Galaxias paucispondylus (Stokell, 1938)
Alpine galaxias are difficult to distinguish from dwarf galaxias, but Alpine galaxias have 16 caudal and 7 pelvic fin rays compared to 15 and 6, respectively, in dwarf galaxias. There are also white chevron-shaped marks in front of the dorsal fin on alpine galaxias. Although these marks are only visible on live specimens, they can be used to distinguish alpine galaxias from Canterbury galaxias and koaro. In addition, alpine galaxias have a more slender, elongate shape than Canterbury galaxias or koaro.
Alpine galaxias have a similar life cycle to longjaw galaxias, and they inhabit many of the same streams at mid to high altitudes draining to the east coast of the South Island. However, alpine galaxias generally live in deeper, swifter water than longjaw galaxias, and their distribution extends further south into Southland. These two species have overlapping diets, but the alpine galaxias reaches a larger maximum size (112 mm) than the longjaw galaxias (87 mm).
Salmo salar (Linnaeus, 1758)
As its name implies, the Atlantic salmon is native to the continents bordering the Atlantic Ocean in the Northern Hemisphere. There, it is a highly prized sports fish renowned for its large size and fighting abilities. Although early settlers in New Zealand were eager to establish Atlantic salmon populations here, most introductions were not successful and feral stocks are confined to the upper Waiau River catchment where it is considered to be close to extinction. Breeding stocks of Atlantic salmon are maintained at the Otago Fish and Game Council hatchery in Wanaka.
Atlantic salmon closely resemble brown trout, but are a more slender, elongate fish. The caudal peduncle is also longer; if the anal fin is folded up against the body, it does not reach the base of the caudal fin. Atlantic salmon have dark backs, fading to a silvery colour below the lateral line. The back and sides are covered in small, darker spots but these generally do not extend below the lateral line. There are no spots on the tail.
In their native waters, adult Atlantic salmon live in the sea and migrate to their freshwater spawning grounds in winter. Unlike the Pacific salmon species, Atlantic salmon can spawn more than once. In New Zealand most adults reside in lakes and migrate upstream for spawning. Spawning here also occurs in winter.
Anguilla reinhardtii (Steindachner, 1867)
This freshwater eel is normally found on the east coast of Australia from Cape York to Tasmania. How and when it arrived in New Zealand is somewhat of a mystery but might be related to changes in the oceanic currents that transport the passive larvae from the spawning grounds in the South Pacific. The presence of Australian longfin eels in New Zealand waters was confirmed in 1997 using vertebral counts and DNA markers from eels caught in the Waikato River. Nineteen eels from age 4 to 11 years were examined during this study. Although this confirmation is recent, anecdotal evidence suggests “reinhardtii” may have been in New Zealand for at least 25 years.
The Australian longfin has conspicuous black blotches all over its body except on its belly. This is the easiest way of distinguishing it from the New Zealand longfin. It has only been officially identified from the Waikato River, but mottled eels have been reported on the west coast from Northland to Taranaki and also on the east coast of the Coromandel, and it may be moderately widespread in the northern North Island.
Although the habitat of the Australian longfin overlaps that of the New Zealand longfin, there is little danger than the Australian longfin will edge out our native species. This is because researchers believe that each eel species has a single spawning ground and it is therefore unlikely that a separate breeding stock would be established for “reinhardtii” that reside in New Zealand. It is thought that their arrival here will continue to be erratic and intermittent, although the confirmed presence of several year classes suggests migration here is certainly more than an isolated event.
Galaxias fasciatus (Gray, 1842)
This member of the Galaxiidae family is one of the five species that occur in the whitebait runs that enter our rivers each spring. Banded kokopu are generally the smallest of the five species when they are whitebait and have an overall golden colour. The juveniles are very good climbers and will often escape from buckets by clinging to and wriggling up the sides.
Adult banded kokopu can be distinguished from the other galaxiid species by the presence of the thin, pale, vertical bands along the sides and over the back of the fish. These bands begin to develop quite early, but similar bands also appear on juvenile giant kokopu, and it is easy to confuse young fish of these species. It is probably best to send small specimens to a fish biologist for identification. Banded kokopu commonly grow to over 200 mm, and fish of this size should be no problem to identify correctly.
Adult banded kokopu usually live in the pools of very small tributaries where there is virtually a complete overhead canopy of vegetation. This vegetation does not have to be native bush, however, and banded kokopu happily live in urban streams and streams under exotic pine plantations so long as overhead shade is present. They only occur in pools where there is instream cover such as an undercut bank, large rocks or wood debris. They depend on terrestrial insects for a large proportion of their diet and can detect the small ripples made by moths and flies that become stuck on the water surface of the pool.
Although the juveniles are good climbers, banded kokopu do not penetrate very far inland and are primarily a coastal species. They are found on Chatham and Stewart Island, but occur only in New Zealand. Banded kokopu are rare along the east coast of the North Island south of East Cape and down the east coast of the South Island, but common elsewhere. This distribution is probably a result of intensive land development and the sensitivity of the juveniles to suspended sediments. Rivers containing glacial flour or eroding sedimentary catchments are not attractive to the whitebait of this species.
Galaxias macronasus (McDowall & Waters, 2003)
The bignose galaxias is yet another non-diadromous galaxiid from the South Island that has only recently been described. It was distinguished as a new species based on DNA sequencing and its morphology. The bignose galaxias is closely related to what are referred to as the “pencil galaxias”, small, slender (pencil-shaped), non-diadromous, mainly sub-alpine galaxiids with small fins and long, slender caudal peduncles (G. divergens, G. paucispondylus, G. prognathus and G. cobitinis). It can be distinguished from these species because it has only 4–6 pelvic fin rays (usually only 5) and only 11–14 caudal rays. It also has a distinctly rounded lateral head profile with the upper margins of the eyes being well below the dorsal profile.
Bignose galaxias are found in several locations in the Mackenzie Basin in the upper Waitaki River catchment. Generally it is found in small spring or wetland-fed tributaries. Little is know about its life history, although this is probably similar to the other pencil galaxiids. Sexually mature fish were found in June and July, suggesting spawning takes place in winter.
Rhombosolea retiaria (Hutton, 1873)
The black flounder is the only member of the flatfish family, or Pleuronectidae, that is a truly freshwater species. Other members of the family, such as the yellowbelly flounder, occasionally wander into the lower reaches of rivers, but do not usually stay there. As their name implies, the flatfishes are indeed flat, and have adopted a habit of laying on their sides right down on the substrate. Both eyes are on their dorsal or upper side to improve their field of view.
Because of their unusual shape, flounders are unlikely to be confused with other fish species except other flounders. The black flounder is easily distinguished from other flounders by the colouration; the top of the fish is usually dark-coloured with numerous, obvious brick-red spots. Flounders can grow to about 450 mm in length, although 200–300 mm fish are more common.
The black flounder is found throughout New Zealand but is unique to this country. They have not been reported from Chatham or Stewart Island. They are primarily a coastal species, although they can penetrate well inland if the river gradient is not too steep; specimens have been recorded more than 100 km inland in some river systems.
Little is known about the life cycle of the black flounder. The larvae are undoubtedly marine, but where and when spawning takes place is a mystery. Black flounder are a carnivorous species and probably eat a variety of bottom dwelling insects and molluscs. They are also known to feed on whitebait during the spring migration.
Neochanna diversus (Stokell, 1949)
In many respects the black mudfish is similar to the brown mudfish except that it occupies the northern part of the North Island. Its distribution pattern is a good way to tell it apart from the brown and Canterbury mudfish, but the distribution of the newly discovered Northland mudfish overlaps that of the black mudfish. Black mudfish can be distinguished from the Northland mudfish by the number of caudal fin rays; the Northland mudfish has only 13 or fewer rays whereas the other mudfish usually have 14 or more.
Black mudfish live primarily in swamps and wetlands and are found from the Mokau River catchment in the south up to Kaitaia in the north. They are quite abundant in the Waikato region, particularly in Whangamarino Swamp, and also occur on the Hauraki Plains. They have a similar life history to brown mudfish, with spawning taking place at the beginning of the wet season and probably continuing through to early spring.
In addition to the threat to black mudfish from land drainage and development, these fish are also threatened by the presence of gambusia, an aggressive and prolific introduced fish that has a similar distribution pattern to black mudfish. Observations of their behaviour in tanks showed that large gambusia would readily eat mudfish fry, and that they chased and nipped juvenile mudfish. However, adult mudfish were not harassed, and even attacked the gambusia. Mudfish are able to co-exist with gambusia because they can survive in habitats that periodically dry up, which gambusia cannot do, and because they breed in winter, when gambusia numbers are low.
Gobiomorphus hubbsi (Stokell, 1959)
The bright blue gill cover just behind the head readily distinguishes the aptly named bluegill bully from other members of the Eleotridiae family. Small dark spots that cover their cheeks are another useful characteristic. When viewed from the top bluegill bullies are arrow shaped, with their narrow elongate body trailing behind the larger head.
Bluegill bullies inhabit similar habitat to torrentfish - swift broken water in open rivers and streams. They also have a similar distribution pattern to torrentfish, being absent from Fiordland, Stewart and Chatham Island, and rare in Otago and Southland. Overall, they are not as common as torrentfish, particularly in Taranaki and Coromandel.
Bluegill bullies are the smallest members of the Eleotridiae family in New Zealand. The largest specimen recorded is a 100 mm bully, but most adults are between 60–70 mm in length. In common with all the bully species, bluegill bullies are benthic. Bluegill bullies are strictly carnivorous, and their food is mainly mayfly larvae. Males grow larger than the females and the larger fish (both sexes) are found further upstream than the smaller ones.
Salvelinus fontinalis (Mitchill, 1814)
This native of the eastern North American continent was first introduced to New Zealand in the late 1870s or early 1880s. Brook char have been released in virtually all the main catchments on the east coast of the South Island, and they were also widely introduced in the North Island although they now occur in only 3-4 rivers in the Central North Island. Although many populations have now become established in the South Island, river-dwelling brook char are confined to the very small tributaries where they do not have to co-exist with other salmonids. Here they can reach maturity, but they tend to be stunted (small in size) and thus are not usually fished for. Several lake populations have also become established, and these are more popular with anglers. In particular, Lake Emily in the Ashburton River catchment yields brook char up to 2 kg in weight.
Brook char are an attractive, brightly coloured member of the Salmonidae family. In fact their colouration is a good characteristic to use to distinguish them from the other salmonids. Their bodies are generally dark with marbling present on the back. Their sides are covered with gold and red spots, the latter of which are surrounded by pale blue halos. In addition, there is a distinctive white stripe followed by a contrasting black stripe on the leading edge of the pelvic, pectoral and anal fins. Brook char also have a very large mouth that extends back behind the posterior margin of the eyes.
Neochanna apoda (Günther, 1867)
Mudfish are probably one of the least known freshwater fish. There are five species in New Zealand, and they have become specialised for life in a distinctive type of habitat – swamps, drains, and forest pools that tend to dry up in summer. They can exist in these habitats because they have the ability to survive out of water during drought. In fact, the first records of these fish often came because specimens were discovered curled up in the mud when wet areas were dug up for drainage or cultivation.
Mudfish are an elongate, slender-bodied fish with blunt heads and small eyes. Three of the five species lack pelvic fins, and this is the easiest way to distinguish them from other members of the Galaxiidae family.
The brown mudfish occupies central New Zealand, from Taranaki, through Wellington and the Wairarapa, and down the northwest coast of the South Island. As its distribution does not overlap with the other mudfish species, there is little chance of confusing this species with the others.
Studies show that mudfish mature during the summer aestivation period and spawn as soon as their habitat is re-inundated in the autumn. This gives the larvae the longest possible period with water present in which to develop and grow. Not all brown mudfish aestivate as some live in permanent water. These populations may spawn at any time of the year. Brown mudfish reach a maximum age of at least seven years and grow to about 150 mm in length.
Salmo trutta (Linnaeus, 1758)
Brown trout are native to Europe and were first introduced into New Zealand in the late 1860s from British stock that was first established in Tasmania. Many subsequent introductions have occurred, and brown trout are now the most widespread and common introduced fish in New Zealand waters. Brown trout have been introduced to at least 40 other countries worldwide, including Australia, South Africa and countries in South America.
The colour pattern of brown trout varies with their habitat. Sea-run and lake fish tend to be silvery with brown and olive spots of varying intensity, whereas river-dwelling fish are darker with dark brown and red spots, the latter being surrounded by paler halos. These red spots are particularly prominent on small river fish. Brown trout seldom have any spots on their tails, a feature that distinguishes them from rainbow trout. Brown trout closely resemble the Atlantic salmon and both occur in the Lake Te Anau system. Brown trout are generally stockier, and have a deeper and shorter caudal peduncle than Atlantic salmon. They also have a shorter-based and deeper anal fin than chinook or sockeye salmon.
Brown trout are primarily a freshwater species, but can spend time in the sea. One specimen that was tagged near Christchurch was later recaptured in the Mataura River, while another tagged in the Wanganui River system turned up in Taranaki 125 days later. Spawning, which occurs in autumn and early winter, takes place in fresh water. Brown trout do not undertake extensive spawning migrations like some of the other salmonids, but some movement does occur, particularly for lake populations. Like all salmonids, the female digs a redd where the eggs are deposited.
Although the brown trout fishery does not receive as much publicity as that for rainbow trout, these fish are highly prized by anglers because they are considered much harder to catch. Specimens up to 14 kg in weight have been recorded in recent times, but a fish over 5 kg would cause any angler to smile.
Brown trout occur virtually everywhere in New Zealand south of Auckland. Populations in the northern North Island are limited because winter water temperatures are probably too warm for successful egg development. Although brown trout have spread to Fiordland, they have not become established on Chatham or Stewart Islands.
Galaxias vulgaris (Stokell, 1949)
The Canterbury galaxias is a non-diadromous galaxiid that inhabits low to high altitude rivers and streams in the Canterbury Plains. Previously, the Canterbury galaxias and the Otago/Southland galaxiids were thought to be the same species, but DNA analysis revealed that the Canterbury galaxias is different to the others. The Otago/Southland group has now split into eight species, although three of these await formal recognition. Detailed study of the Canterbury galaxias shows that more than one species occurs in this region as well. The new and as yet undescribed species is thought to occur in the northern part of the range – from the Clarence River north.
There are three galaxiid species that co-exist with the Canterbury galaxias and that might be confused with this species. Alpine and longjaw galaxias are relatively easy to distinguish, but the koaro is more difficult. Both the alpine and longjaw galaxias are very slender fish, and when alive, the alpine galaxias has distinct white chevron-shaped marks at the front of the dorsal fin. The long, protruding jaw of the longjaw galaxias is unmistakable. In koaro, the lower jaw is obviously shorter than the upper jaw, and this feature can be used to tell it apart from the Canterbury galaxias. Koaro also have a bolder colour pattern with sparkling gold highlights whereas the colouration of the Canterbury galaxias tends to be more subdued. However, colour can vary so much in individual fish that this is not an infallible characteristic to use for identification.
Studies show that Canterbury galaxias spawn in September and that mortality of adults can be high after spawning. The male fish excavates a primitive nest, usually under a boulder, and probably mates with several females. Although he guards the nest for a period while attracting females to breed, there is no evidence of any parental care of the eggs or larvae.
Neochanna burrowsius (Phillipps, 1926)
As its name implies, this mudfish species is restricted to the Canterbury region. This is the best feature for distinguishing it from the other mudfish, but the presence of pelvic fins on the Canterbury mudfish is also a unique feature of the mainland mudfish species. The Canterbury mudfish can be distinguished from other members of the Galaxiidae family by the presence of fewer rays in the pelvic fins (4 or 5 rays for Canterbury mudfish compared to 7 in the other galaxids). They also have comparatively small eyes.
The Canterbury mudfish is found from just north of Christchurch down the east coast to the Waitaki River. It has never been found south of there. It occupies weedy springs, drains, and irrigation races at low to mid altitudes across the plains and it does not usually co-exist with other fish species, probably because they frequent habitats that are subject to drying up in summer. Like the other mudfish species, it can aestivate when its habitat dries up and it remains buried in its hole in the mud until the water returns.
Canterbury mudfish lead a precarious existence and are considered to be a rare species. The development and drainage of swampy lands and subsequent lowering of the water table have probably contributed to their decline by reducing and fragmenting their habitat. Recently, a release of Canterbury mudfish occurred in a protected wetland near Willowby south of Ashburton, where it is hoped they will survive and reproduce. The establishment of similar populations in other protected wetlands is also desirable if we are to ensure that this unique New Zealand fish does not disappear.
Ameiurus nebulosus (Lesueur, 1819)
The catfish is not native to New Zealand and is the only member of the Ictaluridae family that occurs in New Zealand waters. The Ictaluridae, or North American catfish, is one of the smallest of more than 30 catfish families worldwide with about 45 species. Ictalurids are characterised by having barbels around the mouth – these look rather like whiskers and hence the common name catfish. However in North America, where there are many species of catfish, the species found in New Zealand is known as the brown bullhead.
The brown bullhead catfish is dark brown to olive green colour with paler sides and bellies. In addition to the eight distinctive barbels around their mouth, catfish also have relatively small eyes and a smooth skin. The leading edge on their dorsal and pectoral fins has a sharp spine, and thus catfish should be handled very carefully to avoid injury from the spine. Catfish are an extremely robust fish and can survive for long periods out of water. They commonly grow to 200–300 mm in length.
Catfish have been present in New Zealand since the late 1800s. For many years, they were rarely encountered with the only known populations occurring in the lower Waikato River and in Lake Mahinapua south of Hokitika. They were first recorded from Lake Taupo in 1985. Since then, catfish have gradually spread throughout Lake Taupo and down the Waikato River. In 1997, catfish were recorded for the first time from the Kaituna Lagoon near Lake Ellesmere, and in 2003 from a stream entering Hokianga Harbour. Accidental introductions via boat trailers and especially fyke nets used for eeling is continuing to spread this species around New Zealand.
Catfish spawn in shallow depressions on the substrate in the shallows. The male guards and fans the eggs during development, and also guards the larvae for about a week after hatching. Catfish are carnivorous and use their sensitive barbels to probe the substrate and locate insects, crustaceans, molluscs and small fish. Freshwater crayfish are a major prey species for catfish in Lake Taupo.
Neochanna rekohua (Mitchell, 1995)
As its name implies, this member of the Galaxiidae family is found only on Chatham Island and it is therefore unlikely to be encountered by most New Zealanders. It was discovered in 1994 and at present is only known from remote peat lakes on the southern part of the island. It can be distinguished from most other mudfish by the presence of well developed pelvic fins, and from other galaxiids by the deep caudal peduncle with strong dorsal and ventral flanges. Juvenile Chatham mudfish resemble inanga, but the two species do not co-exist. The Chatham mudfish apparently lives its whole life in fresh water; although little is known about it.
Oncorhynchus tshawytscha (Walbaum, 1792)
Chinook salmon are one of three Pacific Salmonidae from the genus Oncorhynchus that has become established in New Zealand. Native to the northwest coast of North American and northeast Asia, the specific name of this fish (pronounced shaw-witch-shaw) comes from the Kamchatka Peninsula and is thought to refer to their distinctive black gums. This character can be used to distinguish chinook salmon from the other Salmonidae in New Zealand. This species is also known as quinnat or king salmon.
Chinook salmon in New Zealand have a life cycle that is typical of salmon in the North Pacific. The adults grow to maturity in the sea and migrate upstream to spawn, usually when they are three years old. After spawning, which occurs in autumn, all of the adults die. Juveniles hatch in spring, and typically spend 3 months in fresh water before migrating downstream to enter the ocean in summer. In some populations, a second downstream migration, consisting of individuals that have spent a year in fresh water, occurs the following spring.
Chinook salmon are a highly prized sports fish in New Zealand although the population is not large enough to support commercial fishing. However, there are a number of successful salmon farms in New Zealand, and it is possible to buy fresh chinook salmon in most supermarkets nowadays. When the spawning migration of adult fish is in progress between December and April, picket lines of eager anglers are a common sight at major river mouths along the east coast of the South Island. Salmon lose condition as they migrate upstream and thus the most prized fish are those caught soon after arrival in fresh water. Chinook are the largest Salmonidae in New Zealand, commonly reaching 10–15 kg in weight.
Chinook salmon occur mainly on the east coast of the South Island from the Waiau River in the north to the Clutha River in the south. The main runs occur in the large braided rivers – the Waimakariri, Rakaia, Rangitata and Waitaki. There are also small runs in the Paringa, Taramakau, and Hokitika River on the west coast, but other records of Chinook salmon on the west coast are probably stray fish. A few land-locked stocks are also known from lakes along both the east and west coasts. Although juvenile fish have been caught in some North Island rivers, indicating successful spawning had occurred, there are no consistent runs of Chinook salmon in the North Island.
Gobiomorphus cotidianus (McDowall, 1975)
There are three other bully species that are easily confused with common bullies, and identification is difficult without a microscope. Sometimes faint vertical lines along the cheek are a good characteristic, but this is not always reliable. The location of head pores and the scale pattern on the head are used to distinguish common bullies from Crans and upland bullies, whereas the number of spines in the first dorsal fin distinguishes common from giant bullies. Both of these characteristics are difficult to see in the field. The situation is further complicated by the wide overlap in the distribution of bully species.
Common bullies are everywhere in New Zealand. Sea-going populations occur in river and streams near the coast, and land-locked populations have become established in many of our lakes where they are an important prey species for trout and eels. In rivers, they mainly inhabit still or slow-flowing waters and thus are probably one of the most likely bullies to be seen. In lakes, the larvae are planktonic and feed on zooplankton. Eggs are laid on the undersides of hard substrates (wood, rock) in both lakes and rivers, and the egg patches are defended by a male.
Apart from a few records from Stewart and Great Barrier Island, common bullies are largely confined to the mainland in New Zealand. Like all the bully species, common bullies are unique to New Zealand. Common bully can grow to a large size; specimens over 120 mm are not unusual.
Retropinna retropinna (Richardson, 1848)
There are two New Zealand species in the Retropinnidae family, the common smelt and Stokells smelt. This family of fishes, known as the southern smelts, is also found in Australia, but the two species we have here are unique to this country. Smelt can be distinguished from other species by the presence of the adipose fin, a small fleshy lobe on their back between the dorsal fin and the tail. They also have scales, a distinctly forked tail, and a cucumber-like smell. The two species that live in New Zealand are very difficult to tell apart, and positive identification depends primarily on the size and number of the scales.
Smelt are a shoaling species, which means they swim in schools near the water surface rather than resting or hiding on the substrate. Thus, they are often seen out in the open in streams and lakes as they feed on drifting food organisms. The common smelt is widespread throughout New Zealand, including Stewart and Chatham Island. They live in flowing and still water, and there are both diadromous (sea-going) and non-diadromous (land-locked) populations in New Zealand, although humans have established many of the latter. Although they are not a climbing species, smelt are good swimmers and will penetrate well inland in river systems that are not too steep (e.g. the Wanganui or Manawatu Rivers). They are particularly abundant in the Waikato River catchment.
Of the freshwater fish that live in New Zealand, smelt are one of the most sensitive to pollutants like ammonia and stressors such as high water temperature. In some cases, they are as intolerant as the salmonids, which are often used as a benchmark species overseas for establishing water quality guidelines to ensure fish are protected from human activities. Smelt are therefore an appropriate native species for establishing guidelines for New Zealand waterways and usually their presence indicates that the water quality is suitable for most other fish.
In most North Island lakes, smelt are the main prey species for trout. In rivers, juveniles are often captured by whitebaiters as they migrate upstream and mix with the whitebait (galaxiids).
Gobiomorphus basalis (Gray, 1842)
Crans bully is another non-diadromous member of the Eleotridae family. They are stocky little fish that are hard to distinguish from common and upland bullies, whose distributions overlap that of Crans bully. On mature males, the top edge of the first dorsal fin is a bright pinkish-orange, but this is not a useful identification characteristic for small bullies and females.
Crans bully is strictly a North Island fish and is found in most areas. Its rarity in the arc northeast of Lake Taupo is thought to be a long-lasting effect of the Taupo eruption over 1800 years ago. As Crans bully has no marine phase, their ability to colonize new river systems is limited, and once they are gone from an area it is unlikely they will re-colonize on their own.
With no requirement to go to the sea, Crans bully is most common at sites at mid altitudes and some distance inland. It dwells in stony rivers and streams and does not establish lake populations. Breeding behaviour is similar to the other bullies, with the male establishing a territory, and remaining to guard the eggs after they are laid.
Parioglossus marginalis (Rennis & Hoese, 1985)
The genus Parioglossus comprises about 13 species found throughout the tropics of the Indo-West Pacific oceans. The recent discovery of a Parioglossus species on Great Barrier Island and in Northland is the first record of any fish from this genus in New Zealand waters. The species found here, the dart goby, is native to the east coast of Australia. How and when it arrived here is unknown, but ship ballast water is one possibility.
Superficially, the dart goby resembles a bully. However, there is no gap between the two dorsal fins, and the scales are very tiny, almost invisible. These features easily distinguish the dart goby from the bully species. The dart goby is also very small, with a maximum size of about 40 mm.
Generally, members of the Parioglossus genus inhabit marine and estuarine waters. The two known New Zealand locations of the dart goby are at least partly seawater. The Great Barrier site occurs in a low gradient wetland where the tidal wedge penetrates inland, and the Northland site is a small, brackish, coastal stream. However, laboratory tests showed that the dart goby could tolerate fully fresh water for at least a fortnight.
Very little is known about the life history or ecology of the dart goby, either here or in Australia. The extent of its distribution within New Zealand is also unknown. This makes it difficult to consider what impacts its introduction might have on the native flora and fauna. Such knowledge will only come after further surveys and studies on this little known fish.
Galaxias pullus (McDowall, 1997)
The dusky galaxias is a new addition to the Galaxiidae family that was formally described in 1997. It has a restricted distribution in the Otago region in tributaries of the Taieri and Clutha River catchments. Although it occurs in the same general area as another of the new Otago galaxiids, Eldons galaxias, the two species have never been found together.
The dusky galaxias differs from the other galaxiids in having only 14 caudal fin rays compared to 15 for Eldons and dwarf galaxias and 16 for the others. It is generally a brown colour, but with a distinct dark and light colour pattern. It also has darker blotches behind the gill openings that are more characteristic of the diadromous banded and shortjaw kokopu. Adults are commonly up to 110 mm in length, although specimens of 150 mm have been recorded.
The dusky galaxias lives in tussock and forest streams at mid to high elevations (400-1000 m), utilizing riffle and pool habitats. Spawning occurs in spring with the fish laying their eggs under overhanging banks in riffles. These fish eat a wide variety of aquatic insects and occasionally terrestrial items that fall in the water.
Galaxias divergens (Stokell, 1959)
The scientific name for this species indicates that it diverges from the other members of the Galaxiidae family: it has only 6 pelvic fin rays compared to the more usual 7 for the other galaxiids. The number of caudal fin rays (15) is also different from most other galaxiids, except for Eldons galaxias. However, dwarf and Eldons galaxias do not co-exist, with Eldons galaxias being confined to Otago.
The dwarf galaxias is amber to olive green in colour with dark brown blotches on the sides and back. The belly is silvery. The whole life cycle of the dwarf galaxias occurs in fresh water, and the maximum size of these fish is about 90 mm, although most adults are usually less than 70 mm in length. Aquatic larvae of mayflies and midges are the most commonly eaten foods of the dwarf galaxias.
Of the non-diadromous members of the Galaxiidae family, the dwarf galaxias has the widest distribution, although this pattern is extremely fragmented. In the North Island, dwarf galaxias occur in the headwaters of the Waihou River near Putaruru, at a few sites in the Rangitaiki River near Galatea, in Hawkes Bay, and the Wellington region. In the South Island, it occurs in Marlborough and Nelson, and on the west coast as far south as the Hokitika River. Recent studies show there are some genetic differences between the populations, but probably not enough to warrant any separate species.
Galaxias gracilis (McDowall, 1967)
The dwarf inanga looks like a small inanga and is closely related to inanga. However, it is found in only 13 lakes near Dargaville in the North Island. As its name implies, it is the smallest member of the Galaxiidae family in New Zealand. Specimens of over 80 mm in length are rare, and mature adults may be only 40 mm.
Juveniles school around the lake edges where rushes and macrophytes provide shelter from predators. They feed on zooplankton in open waters at night. Adults occur in deeper water near the middle of the lake and return to the littoral zone at night to feed on the larger invertebrates present there
Dwarf inanga populations have declined over the past 30 years, and it is now considered to be a threatened species. The introduction of rainbow trout into some of the lakes it inhabits (especially the Kai Iwi lakes) was initially blamed for this decline, as trout are known to eat inanga. However, removal of trout from one lake did not increase the abundance of dwarf inanga and, up until 2000, it was abundant in Lake Ototoa which was routinely stocked with trout. Gambusia is now thought to be responsible for its scaricty in Lakes Taharoa nd Waikere, and for its extinction in Lake Kai Iwi.
Galaxias eldoni (McDowall, 1997)
This member of the non-diadromous galaxiid group has a very restricted distribution; it is confined mainly to tributaries in the lower to mid Taieri River catchment. This is another new Otago galaxiid species and it was first formally described in 1997. The name honours G.A. Eldon, who assissted Dr R.M. McDowall with his investigations into the galxiidae. Eldons galaxias closely resembles the flathead galaxias, but it has a deeper body and darker colouration, especially in large individuals. Its can also be distinguished from the flathead and other galaxiids by the number of caudal rays (15 in Eldons, 16 in the flathead, and 14 in the dusky galaxias). It shares this characteristic of 15 caudal rays with the dwarf galaxias, but their distributions do not overlap.
Although the full extent of their occurrence is not yet known, it appears that the distribution of Eldons galaxias is highly fragmented. This may be caused by competition from the introduced salmonids: brown trout, rainbow trout and brook char. The establishment of land-locked populations of native koaro in Lake Mahinerangi may have also affected their distribution.
Eldons galaxias reaches a maximum size of about 150 mm and are commonly found up to 110 mm long. Like most of the non-diadromous galaxiids, Eldons galaxias feeds on aquatic insects, occasional terrestrial items, and on rare occasions, small koura. They can often be seen during the day feeding on items drifting downstream.
Eldons galaxias tends to prefer riffle habitats, but can also be found in pools. They occupy a diverse range of streams from high altitude tussock streams to low altitude forested ones. Often they are found upstream of large waterfalls that restrict the distribution of salmonids. Spawning occurs in mid-spring, and the larvae hatch about a month or so later.
The estuarine triplefin is primarily a marine species, but it also occurs in river estuaries throughout New Zealand. It can be easily distinguished from other freshwater species by the presence of the three dorsal fins, a feature it shares with other members of the Tripterygiidae family. Although the other members of the family are strictly marine dwelling, there are a number of poorly differentiated species and the taxonomy of this family is in confusion. Until fairly recently, this species was known by the scientific name of Tripterigion nigripenne, but it has had several other names over the years, including T. robustum and T. varium. The current consensus is that it belongs in the Grahamina genus, with the specific name still in doubt.
The estuarine triplefin is found throughout New Zealand and is probably much more common that the distribution map indicates. This is because it probably does not actually live in flowing fresh waters, only going upstream as far as the tidal influence extends. Tidal habitats are difficult to sample with conventional methods. It is also an abundant species on rocky shores along the coast. Triplefins reach maturity at about 55 mm in length, and commonly reach sizes of 80–100 mm.
Breeding in triplefins appears to occur over an extended period from winter through summer. Like members of the Gobiomorphus genus (bullies), male triplefins establish and defend territories during the breeding season, and try to attract and breed with as many females as possible. After the eggs are laid in a primitive nest, which is usually the underside of a large rock, the male remains to guard them until hatching.
Galaxias depressiceps (McDowall & Wallis, 1996)
The flathead galaxias is another of the recently discovered non-diadromous Galaxiidae that are only found in Otago, primarily in the Taieri River catchment. It was formally described as a new species in 1996, and its scientific name refers to its distinctly flattened (depressus) head (ceps). Other non-diadromous galaxids with flat heads have been found in the Clutha catchment and in Southland, but recent comparisons by Otago University suggest these are distinct from G. depressiceps with 3 new species awaiting formal recognition. Clearly, sorting out the taxonomy of the Otago/Southland galaxiid complex is going to take more time.
At present, this species of flathead galaxias is known mainly from streams in the Taieri catchment, but also the Shag, Waikouaiti and some coastal streams south of the Taieri. The flathead galaxias is difficult to distinguish from some of the other galaxiids that appear to be restricted to the Taieri catchment, although the number of caudal fin rays can be used to distinguish flathead galaxias (16 fin rays) from the dusky (14 fin rays) and Eldons galaxias (15 fin rays). Telling flathead galaxias apart from roundhead galaxias and koaro, also with 16 caudal fin rays, is more difficult, relying on the teeth, colour pattern, and the flattened head. Flathead galaxias often also have a golden stripe down the centre of the back to the dorsal fin and a golden belly. These three species never occupy the same stream, but koaro and flatheads or roundheads and flatheads do co-exist, albeit at few sites.
The distribution of the flathead galaxias is fragmented, possibly a consequence of impacts from the introduced brown trout. The preferred habitat for this species is cobble/boulder streams in tussock grasslands, and most populations occur above large waterfalls. Flatheads are found at altitudes of 140-1130 m in Otago, and they can live in steep mountain streams. Flatheads reach a maximum size of 168 mm, but are usually less than 125 mm.
Gambusia affinis (Baird and Girard, 1854)
In their native waters surrounding the Gulf of Mexico, gambusia are renowned for their ability to eat large numbers of mosquito larvae and are also commonly called mosquitofish. This ability led to their introduction into many countries where mosquitoes were perceived to be a problem, resulting in gambusia possibly being the most widespread fish in the world today. Their arrival in New Zealand is not well documented, but probably occurred in the 1930s when a population was established in an Auckland pond. Since then, they have been steadily spread thoughout the North Island. A number of wild populations were discovered around Nelson after 2000 but most of these have now been erdicated to restrict its spread in the South Island.
Compared to some of the other Poeciliidae, gambusia are rather drab, although the darker margins on their scales give them a crosshatch pattern. Gambusia are relative small fish: females may reach 60 mm in length, but males are usually less than 40 mm. Mature females often have a large black blotch behind the operculum and mature males are charactersied by their elongated pelvic fins which from a gonopodium.
Gambusia makes up for its small size by being an extremely aggressive species and attacks on some native fish species have been well documented globally as well as in New Zealand. Overseas, they have also reduced a number of frog and dragonfly species. Their value as a mosquito control agent is questionable and clearly they are an unwanted species so their spread should be prevented.
Gobiomorphus gobioides (Valenciennes, 1837)
As its name implies, the giant bully is the largest member of the Eleotridae family in New Zealand. Specimens of over 250 mm in length have been reported, although fish in the 120-150 mm range are more common. It is virtually impossible to distinguish the giant bully from the common bully unless you count the number of spines in the first dorsal fin. In giant bullies there are always six spines and in common bully there are usually seven. However, these are difficult to count in the field unless you have some forceps because the spines tend to collapse when the fish is out of the water. Size alone is not a good indicator because common bullies can also grow to 150 mm.
The life cycle of giant bullies is somewhat of a mystery. The larvae are thought to have a marine phase, but no juvenile giant bullies have ever been positively identified. In fact, few giant bullies of less than 80 mm have been recorded. Whether small giant bullies have not been distinguished from common bullies or whether they live elsewhere is not known. The adults are never found more then a few kilometres inland and it is possible that they may spend a long period in estuaries before moving into fresh water.
Giant bullies have been found in most regions in New Zealand. The slow flowing coastal habitats they live in are difficult to sample although bullies will readily enter fyke nets and traps. To date there have been no studies of this fish so there is no knowledge of its ecological requirements and role.
Galaxias argenteus (Gmelin, 1789)
As its name implies, the giant kokopu is the largest member of the Galaxiidae family. Specimens of over 450 mm in length have been reported, although fish in the 200–300 mm range are far more common. The profusion of golden spots and other shapes on the bodies of larger fish are very distinctive, although small specimens may be difficult to distinguish from banded kokopu. The giant kokopu was the first Galaxiidae to be discovered, and it was its colour pattern that led to the generic name Galaxias, referring to the profusion of stars in the galaxy.
Many people are surprised to learn that giant kokopu are one of the whitebait species. However, giant kokopu are uncommon in the whitebait catch and usually run late in the season. Little is known of their spawning habits. It is thought that the adults migrate to a common spawning site, but spawning has never been observed or any eggs discovered.
Giant kokopu are primarily a coastal species and do not usually penetrate inland very far. They are endemic to New Zealand but are found on the major offshore islands. Like banded kokopu and koaro, they can establish land-locked populations. In streams, they prefer the slow flowing waters that occur in lowland runs and pools. They are also usually associated with some form of instream cover like overhanging vegetation, undercut banks, logs, or debris clusters. It is thought that they lurk quietly in this cover awaiting their prey, which ranges from koura to terrestrial insects such as spiders and cicadas.
Carassius auratus (Linnaeus, 1758)
Most people know goldfish as a popular aquarium fish. Feral goldfish lack the bright colours, bulging eyes and feathery fins of their domestic relatives, but are nevertheless the same species of Cyprinidae. Goldfish have no mouth barbels, a feature that distinguishes them from many of the other Cyprinidae present in New Zealand. The scales are large and the dorsal fin has a long base and 14–20 rays. There are also several thicked fin rays at the front of the dorsal fin, and the last and largest of these is strongly serrated. Wild fish are usually a dark bronze colour.
Goldfish generally live in still waters (ponds and lakes), but also inhabit slow flowing rivers and streams. Spawning occurs in spring and summer when water temperatures exceed about 15°C. The eggs are very small and are spawned in huge numbers. They adhere to aquatic plants and hatch about a week later. There is no parental care of the eggs or larvae. Goldfish are omnivorous and will feed on plant material, detritus, small insects and crustaceans. They commonly reach 150–200 mm in length.
Goldfish were first brought to New Zealand in the late 1860s. Aquarists and breeders carried out further introductions and goldfish are now widespread and well established in the North Island. Their South Island distribution is more restricted, but recent surveys by the Department of Conservation have shown that they are in Nelson, central Otago, Southland and the West Coast. In the early 1900s, feral goldfish populations in central North Island lakes were important to the Maori as a food fish.
Galaxias gollumoides (McDowall & Chadderton, 1999)
This recently described member of the Galaxiidae family was only recognized as a distinct species in the last few years. Because this fish was first found in a swamp and has relatively large eyes, its name refers to its similarity to Gollum, a character in J.R.R. Tolkein's “The Hobbit” and “Lord of the Rings”. Recent studies at Otago University indicated that it occurs on Stewart Island, throughout the Catlins and Southland, and in the Nevis River (which used to drain into the Mataura).
The best way to tell this species apart from other galaxiids is by counting the pelvic fin rays; the Gollum galaxias has 6 pelvic fin rays whereas most of the other galaxiids usually have 7. The two galaxiids that also have 6 pelvic fin rays, Eldons and dwarf galaxias, do not co-exist with the Gollum galaxias.
No detailed studies of its life history have taken place yet, but its life cycle is probably similar to that of the other non-migratory galaxiids, with spawning taking place in spring, and the whole life cycle occurring in fresh water. The largest Stewart Island fish recorded is 75 mm, but Southland populations contain fish up to 150 mm long.
Ctenopharyngodon idella (Valenciennes, 1844)
Grass carp were first brought to New Zealand in the 1960s because of their potential to control the growth of aquatic plants. Unlike the other introduced fish brought to New Zealand, the potential value and impact of grass carp was investigated in secure facilities prior to their use in field trials. Although these fish mature, they have extremely specific spawning and rearing requirements and the establishment of a wild population is extremely unlikely.
There has been much controversy surrounding the use of grass carp as a weed control agent in New Zealand. So far, the main value of grrass carp in New Zealand has been to eradicate problem weed species from lakes, thus allowing native plant communities to re-establish. This means they have a role to play in lake restoration, as well as weed control, but their use for weed control in drains is still being investigated. Today, stocks of grass carp are maintained for breeding at a private hatchery north of Auckland.
Grass carp are a large and robust fish. They commonly exceed 500 mm in length, 10kg in weight, and can live for 15-20 years. Their backs are a dark bronze colour, but this gradually fades to silver on the belly. The margins of their large scales are outlined in a darker colour, giving them a crosshatched appearance. Grass carp have no barbels, but can be distinguished from goldfish by the short dorsal fin with only 7–9 rays.
Prototroctes oxyrhynchus (Günther, 1870)
Most New Zealanders are well aware that some of our native bird species, such as the huia and moa, are now extinct. Few also know that the same is true of one of our native fish species, the grayling. This fish, which is closely related to the smelts, was the only member of the Prototroctidae family in New Zealand. Today, there are probably only a couple of dozen specimens in existence, carefully preserved in museum collections. Fortunately, a closely related species still lives in Australia and studies on this grayling have given us some insight into our own species.
The grayling commonly grew to 200–400 mm in length and was a shoaling species like the common smelt. It was widespread and common in the early 1800s, and appeared to reside in lowland rivers and streams during summer, autumn, and winter. It was New Zealand's only herbivorous fish, grazing on the periphyton present on rocks and boulders. Its life cycle was probably similar to that of the whitebait species and common smelt, with the fish growing and spawning in fresh water, and the newly hatched larvae being washed out to sea to live for several months before migrating back to rivers.
Grayling numbers began to decline soon after Europeans arrived in New Zealand, and as early as the 1870s biologists were expressing concern about their decline. In 1930, they were officially described as being on the verge of extinction by the Marine Department. Why the grayling became extinct is a mystery, but the introduction of trout and widespread forest clearance that rapidly followed European settlement are thought to have contributed to their demise.
Mugil cephalus (Linnaeus, 1758)
The grey mullet is the second member of the Mugilidae (or mullet) family found in New Zealand. In common with the yelloweyed mullet , the grey mullet has two dorsal fins, the first being tall and with four obvious spines. They also have large, easily dislodged scales. Technically, the way to tell the two species apart relies on the presence of the thick fleshy adipose eyelid found on the grey mullet. However, grey mullets also lack the bright yellow eye found on the appropriately named yelloweyed mullet.
Grey mullet have a worldwide distribution and New Zealand is at the southern limit of their range. Hence, they are mainly found in the North Island, and only in the Cook Strait area during the summer months. Although primarily a marine species, grey mullet will penetrate considerable distances upstream. In the Waikato River they are found as far inland as Karapiro Dam and travel up the neighbouring Waipa River to Te Kuiti. However like the yelloweyed mullet, they must return to the sea to spawn.
Grey mullet feed on detritus and plant material that they suck from the substrate. They are also known to feed by grazing the surfaces of aquatic plants. Grey mullet are large fish, commonly reaching 500 mm in length. They are regarded as a valuable food fish, and are particularly nice smoked because of the oily flesh. In many parts of the world they are farmed commercially, but in New Zealand most of the commercial catch comes from fishers operating on Kaipara and Manukau Harbour and in the lower reaches of the Waikato River. Tagging studies of grey mullet in this area showed that there was considerable movement of fish between the river and harbours, and that commercial and recreation fishers extracted a significant proportion of the grey mullet population.
Galaxias maculatus (Jenyns, 1842)
Every New Zealander knows what whitebait are, and most have probably eaten a fritter or two in their time. What many people don't realize is that five separate galaxiid species make up the whitebait catch - inanga, banded kokopu, koaro, shortjaw kokopu, and giant kokopu. In most river systems, the inanga makes up the majority of the whitebait catch, and thus this fish is probably encountered more often than other members of the Galaxiidae family.
Adult inanga are the smallest of the five whitebait species, rarely exceeding 110 mm in length. Their silvery belly and somewhat forked tail make them easy to distinguish from the other galaxiids except for their close relative the dwarf inanga, a species restricted to some dune lakes near Dargaville. Smelt frequent similar habitat to inanga and can be confused with them. However, smelt have scales and an adipose fin, features that are easy to see on close examination.
Inanga inhabit open rivers, streams, lakes, and swamps near the coast and can often be seen shoaling in open water. They are very poor climbers, however, and do not penetrate any distance inland unless the river gradient is very gradual. Inanga are one of the most widespread galaxiids. They occur right around New Zealand and its offshore islands, as well as in South America and Australia.
Over the years, much has been said about the decline of the whitebait fishery and possible reasons for it. Fishing pressure was the target of a recent study on the Mokau River, which used dye-stained whitebait to determine the number of fish that escaped past anglers' nets. This showed that whitebaiters caught a relatively small proportion of the run. However, a parallel study showed that only about 20% of the whitebait that escaped survived to reach adulthood. Historically, their abundance has been greatly reduced nationwide by swamp and wetland drainage. Introduced fish (trout, gambusia) are also thought to have reduced inanga. But today, a reduction is spawning habitat is believed to be the major limiting factor. Inanga spawn on river/stream banks among vegetation inundated by spring high tides. The eggs remain above the water level until the next spring tide when they hatch and are washed out to sea. Modification of the tidally affected regions of stream and river banks by cattle browsing and flood control works have no doubt destroyed much spawning habitat. Because they cannot climb small falls, inanga are restricted to the lower reaches of rivers and stream and their access to good habitat can be greatly reduced by poorly designed culverts.
Galaxias brevipinnis (Günther, 1866)
The koaro is unlikely to be confused with the other diadromous whitebait species because of its shape. It is more elongate and slender shaped, almost like a tube. The sides and back are covered in a variable pattern of light patches and bands that making the koaro a very attractive fish.
Unfortunately, it is not so easy to tell the koaro apart from some of the non-diadromous galaxiids like the Canterbury galaxias and those that live in Southland and Otago. Identification problems are complicated by the fact that koaro can co-habit with the other species in the same rivers and streams. Even the experts have problems separating them, relying on technical measures such as the number of caudal fin rays to ensure correct identification.
Koaro have the ability to penetrate well inland in many river systems, and thus have a more widespread distribution than the other whitebait species. In addition to the mainland, they are also found on Chatham and Stewart Island, in Australia, and on the sub-Antarctic Auckland and Campbell Island.
Rocky, tumbling streams are the preferred habitat of koaro, and they are almost always found in streams with native bush catchments except for tributaries of upland lakes that may be above the bush-line. Studies in Australia found that koaro spawned in damp areas along the edges of the streams they lived in, relying on subsequent floods to inundate the eggs for hatching. A requirement for dampness could explain their preference for forested streams, and shows why their distribution in New Zealand has probably been curtailed by widespread forest clearance, more so than most of the other Galaxiidae.
Although koaro comprise part of the whitebait catch, they also form land-locked populations in lakes. For example, koaro populations occur in the catchments of many of the Rotorua lakes, Taupo, Rotoaira, Manapouri, Tekapo, Pukaki and Wanaka. Koaro populations in lakes were decimated by predation from introduced trout and are now much lower than in pre-European times when they provided a fishery for Maori. In lakes, where smelt have been introduced, koaro have declined even further and are either now confined to tributary streams or have become extinct.
Cyprinus carpio (Linnaeus, 1758)
This brightly coloured member of the Cyprinidae family is a variety of the common carp. The common carp is native to Asia, although it has been introduced so widely and for so many centuries that its precise origins are uncertain. Today, it occurs on every continent except Antarctica. It is not known whether the introduction of koi carp here was deliberate or accidental, but feral breeding stocks were first noticed in the Waikato in 1983. They are now common throughout the lower Waikato system, and have been spread mainly into ponds throughout the North Island. The first South Island record of koi carp occurred in Nelson in 2000, but most of the South Island populations have now been successfully eradicated.
Wild common carp tend to be an olive green colour, but the New Zealand stocks are derived from the highly bred ornamental Japanese koi and thus can exhibit a calico pattern of black, red, orange, gold and white blotches. So far, our feral stocks have not reverted back to the wild colouration. Although their colour pattern is a useful distinguishing characteristic, they also have two pairs of barbels that the other Cyprinidae found here lack.
Koi eat a wide variety of organisms, including both plants and animals. One way they feed is by sucking up and expelling material from the bottom, filtering out edible material as they do so. This habit means that, at high densities in shallow lakes, they can greatly increase the turbidity of the water because they are constantly disturbing the substrate.This makes waterways unattractive and reduces the abundance of aquatic plants. In other countries, common carp have caused such an increase in turbidity that vast amounts of money and effort have been spent trying to eradicate them; unfortunately these have largely been unsuccessful. Although similar problems have not yet been documented in New Zealand, the spread of this fish should certainly be minimised.
Geotria australis (Gray, 1851)
The lamprey spends most of its life in the sea, where it uses a circular sucker to attach itself to other fish. It feeds by rasping a hole in their flesh and then, like a leech, it sucks out a meal of blood. The adults, which are over 400 mm long, spawn in fresh water, and thus migrate into rivers from the sea to spawn in small headwater streams. The adults do not feed while in fresh water and so are not parasitic on freshwater fish, although North American species in the Great Lakes do feed on salmonids.
Lampreys can be distinguished from eels by the presence of the circular sucker instead of a mouth and by the seven gill openings along their sides just behind the head. Male adult lampreys also have large pouches just behind their mouths. When they first come in from the sea, lampreys are bright silvery-blue but soon change to a drab dark grey colour.
We believe juvenile lampreys spend up to four years in fresh water before migrating to the sea. At first they are a muddy brown colour and look like small eels. They appear different from eels by having seven gill openings and no eyes. At this stage, they inhabit sandy banks along the sides of streams. As they approach the size for migration to the sea, juvenile lampreys develop eyes and change to a bright silvery-blue, just like the adults. However, they are only about 100 mm long at this stage.
Lampreys are found throughout New Zealand, and also in Australia and South America. Despite their wide distribution, they have not been reported from Stewart or Chatham islands. Generally they occur close to the coast at low altitudes. On returning to freshwater to breed, adults can use their circular sucker to latch onto and surmount obstacles such as rapids and small falls. Little is known about their breeding habits.
Lampreys were an important food resource for Maori, and elaborate weirs were constructed to catch them. This traditional fishery still occurs on a small scale in the Wanganui River near Pipiriki.
Anguilla dieffenbachii (Gray, 1842)
Longfin eels are distinguished from shortfin eels by the length of the dorsal fin; when viewed side-on, the dorsal fin is longer than the anal fin and extends well forward past the end of the anal fin. In shortfin eels, the dorsal and anal fin ends are almost the same length. Australian longfin eels can be distinguished from native longfins by the presence of irregular black blotches on the back and sides.
Longfin eels are only found in New Zealand and occur throughout the country. The elvers are legendary climbers and penetrate well inland in most river systems, even those with natural barriers such as steep falls. Large hydroelectric dams can also be surmounted if appropriate facilities are provided for eel passage, or if elvers are caught at the base of the dam and stocked into the waters above it. Adults can move overland from one waterbody to another (e.g. from a river to an isolated farm pond) by crossing flat grassy land, especially when it is wet. The longfin eel occupies a wide range of habitats and occurs in rivers, streams, lakes ponds and wetlands. Longfin eels are carnivores and over about 40 cm in length they feed mostly on small fish and crustacea. They are responsible for major commercial and customary fisheries in New Zealand.
Although the longfin eel is endemic and is one of our most common and largest freshwater fish, there is mounting concern at the scarcity of very large specimens which are being rapidly fished out, and longfin elvers are now becoming scarce as well. Pictures of huge eels used to appear regularly in local newspapers, but not any longer. Commercial harvesting is probably mostly to blame for the scarcity of large eels. These are generally females that contain huge numbers of eggs, and are thus important in sustaining the population. So, if you catch a big longfin – put it back in the water instead of feeding it to the cat!
Galaxias cobitinis (McDowall & Waters, 2002)
The lowland longjaw galaxias was first described from specimens caught in the Kauru River, a tributary of the Kakanui River in north Otago. Previously, these longjaw populations were thought to be disjunctive, lowland populations of Galaxias prognathus, the upland longjaw. However, DNA sequencing showed that the Kauru River fish were highly divergent from the other longjaws, and that it is a distinct species. Although its distinctly protruding lower jaw distinguishes this galaxiid from most of the others, it also has only 5 pelvic fin rays, compared to 7 for the other galaxiids, and fewer caudal rays and vertebrae compared to upland longjaws.
Based on its location, the new longjaw species was given the common name of lowland longjaw galaxias. This was unfortunate because recent surveys have shown that this fish also occurs in parts of the upper Waitaki catchment and so is not a lowland species. A single specimen from the Hakataramea River in 1989 was positively identified as a lowland longjaw, but no other longjaws have been found there since. How this species came to be present in such widely separated locations is a mystery, although further surveys may show that it is even more widespread.
Generally, the lowland longjaw looks similar to its upland cousin; it is a slender elongate fish lacking strong colouration. It is also quite small, rarely exceeding 70 mm in length. Adult fish occur in the margins of riffles and runs, but in daylight are usually hidden under rocks and stones. Spawning occurs in late winter and spring, and juvenile longjaws, which lack the distinctly protruding jaw that adults develop, are readily visible in backwaters and side braids from October to January.
Neochanna heleios (Ling & Gleeson, 2001)
The Northland mudfish is a newly discovered member of the mudfish genus. As its name implies, it is only found in Northland and only then from a fairly restricted area near Kerikeri. It can be distinguished from the other mudfish species by counting the caudal fin rays; the Northland mudfish has only 13 or fewer rays whereas the other mudfish usually have 14 or more. The body also has a distinct reddish tinge, particularly on the fins. The largest Northland mudfish on record is 134 mm long, and adult specimens regularly exceed 100 mm in length.
Little is known about the life cycle of the Northland mudfish, although it is undoubtedly similar to that of the other mudfish species. The distribution pattern of the black mudfish overlaps that of the Northland mudfish, but the two species have never been caught together.
The conservation status of the Northland mudfish is uncertain. The largest population occurs in a protected conservation area, but already a separate, smaller population has disappeared in conjunction with deteriorating water quality at the location.
Leuciscus idus (Linnaeus, 1758)
This member of the Cryprinidae family is native to northern Europe where it is valued as a coarse angling fish. Orfe eggs were illegally imported to New Zealand by mail sometime in the 1980s. Subsequent releases occurred between 1985–86 in at least 8 and possibly 5 more sites north of Auckland. The current status of these populations is in doubt; some believe orfe failed to survive in at least 7 of these sites while others are less certain. At least one release site remains unknown and it seems likely that orfe persist in the wild in at least one location in New Zealand.
In Europe, wild orfe are usually greyish brown with silver bellies. However, the variety of orfe present in New Zealand (the golden orfe) is derived from ornamental pond stocks and thus closely resembles rudd. Although it is not known if the two species co-exist, on orfe the scales are smaller and the fins more orange than red coloured. Rudd also have a small projection at the base of their pelvic and pectoral fins. Eventually, the orfe’s golden colouration may revert to the wild type.
Little is known about the biology of orfe in New Zealand. In Europe they primarily inhabit slow-flowing waters. Their food consists of aquatic invertebrates such as worms and snails, but large orfe may consume other fish and aquatic vegetation. Like the other Cyprinidae, orfe are prolific breeders and large females may contain tens of thousands of eggs. Whether they become a nuisance species in New Zealand or will be successfully eradicated remains to be seen.
Perca fluviatilis (Linnaeus, 1758)
Redfin perch belong in the Percidae family, a family of about 60 species that are native to the Northern Hemisphere. One species has become established in New Zealand and it is known simply as the perch. New Zealand perch come from Tasmanian stocks that were originally imported from England. They have become well established in Otago and Southland, but also occur in many other parts of New Zealand, especially around Auckland, the Waikato and in North Island west coast lakes south of New Plymouth.
Perch can be distinguished from other species by the presence of the two dorsal fins, the first having 13–17 firm sharp spines. There is also a broad flat spine on the gill cover. Perch have six or more dark bands along their sides; these are most prominent in small fish. The bottom edge of the caudal fin is bright red-orange, as are the anal and pectoral fins. These features make perch easy to recognize.
Although perch were liberated widely in the late 1870s, there was little interest in their angling potential until after 1990. They are a fine table fish with firm white flesh, but their small size and lack of fighting ability meant that they never became as popular with anglers as the salmonids. Perch are suitable game fish for youngsters because they are relatively easy to catch. Most perch in New Zealand are between 1–2 kg in weight.
Perch prefer slow-flowing and still water habitats. They are strictly carnivorous and adults feed mainly on other fish. Perch have been shown to reduce the abundance of common bullies in lakes. They also reduce inanga, smelt and crayfish in lakes where they have been introduced. At high densities, small fish predominate and can cause toxic cyanobacterial blooms.
Oncorhynchus mykiss (Walbaum, 1792)
Rainbow trout are native to the westward draining rivers of North America and also to the Kamchatka Peninsula on the western side of the Pacific Ocean. Stock introduced into New Zealand were brought from North America as early as 1883. Although they were not as easy to establish as brown trout, self-sustaining populations of rainbow trout are now widespread in New Zealand and form the backbone of the popular and highly valued fisheries that occur in the lakes and rivers of the central North Island. They also support fisheries in many of the lakes along the eastern flanks of the Southern Alps in the South Island.
Like other salmonids, the colour pattern of rainbow trout is variable. Lake-dwelling fish are generally uniformly silver with small, darker spots along the back, mainly above the lateral line. The backs of river dwelling fish are often more olive-green, and the red band, or rainbow, along the lateral line more prominent. When rainbow trout move into rivers and streams for spawning, this band intensifies in colour, and red slashes may occur on the cheeks and in the folds beneath the lower jaw.
Rainbow trout can be distinguished from brown trout and Atlantic salmon by the presence of dark spots on the caudal (tail) fin, and from brook char and mackinaw by the absence of pale spots on their sides. Rainbow trout have a short-based anal fin compared to a long-based anal fin on sockeye salmon. Spawning chinook salmon also develop a red flush along their sides and hence can be confused with rainbow trout. However, chinook salmon have black gums whereas the mouth of rainbow trout is pale in colour.
Most rainbow trout migrate to their spawning grounds, with both lake and river dwelling fish moving upstream to suitable locations, often in small tributaries. Here they may congregate in large schools just prior to spawning. In lakes without suitable spawning tributaries, spawning can occur along the lakeshore. The main spawning season for rainbow trout is June and July, but the season can be extended to October in some lakes, especially those in the colder regions of the North Island.
Although there are no sea-run populations of rainbow trout in New Zealand (usually very large fish known in North American as steelhead), fish 500–600 mm in length and 2–3 kg in weight are the norm in most New Zealand populations. In lakes regarded as trophy fisheries, fish of 4–5 kg are caught regularly.
Gobiomorphus huttoni (Ogilby, 1894)
The bright red fins of an adult male redfin have to make this one of New Zealand's most attractive freshwater fish. Although only males get this distinct colouration, the diagonal stripes on the cheeks make the redfin bully easy to identify. These stripes are even visible in small bullies from about 30 mm in length.
Redfin bullies are strictly diadromous and do not establish land-locked populations. Thus, they tend to live near the coast even though they are very good climbers (populations above 5-m-high waterfalls have been recorded). Spawning takes place in fresh water and after hatching the larvae are swept out to sea. The juveniles enter fresh water in the spring and reach maturity about two years later. This diadromous habit means that they are widespread throughout the country and have been frequently recorded from Chatham and Stewart Islands. However, they are rare along the east coast of the South Island above Oamaru, except for Banks Peninsula.
Redfin bullies occur mainly in the runs and pools of small bouldery streams and their principal food is mayfly, caddis fly and chironomid larvae. Becuase of their dependance on this habitat, they are more sensitive to the effects of siltation in streams than other fish species.
The redfin bully was recognized as a distinct species as early as 1894, but it has had many name changes over the years. The present specific name huttoni honours one of New Zealand's early biologists, Sir Frederick W. Hutton, who was a director of the Canterbury Museum from 1892 to 1905.
Galaxias anomalus (Stokell, 1958)
The roundhead galaxias is another non-diadromous member of the Galaxiidae family that is found only in Otago. It occurs in the Taieri and Clutha catchments, although there is still some uncertainty about the records in the Pomahaka. The map shows our best knowledge of its distribution to date and the description below refers to the Taieri roundhead galaxias.
The number of caudal fin rays can be used to distinguish the roundhead galaxias (16 fin rays) from the dusky (14 fin rays) and Eldons galaxias (15 fin rays), both of which also occur in the Taieri River catchment. The roundhead galaxias, flathead galaxias and koaro all have 16 caudal fin rays, and distinguishing characteristics for these species rely on the teeth, colour pattern, and shape of the head. Although roundheads are only known to co-exist with flathead galaxias in a single stream, and roundheads have never been found with koaro, positive identification is probably best left to the experts.
Roundhead galaxias grow to a maximum size of about 130 mm, but are rarely found larger than 90 mm long. They occupy a diverse range of low gradient streams, from small weedy drains to braided cobble streams. The roundhead is tolerant of high water temperatures and low flows, surviving droughts by living in remnant pools that remain in ephemeral streams. They spawn in early spring, laying their eggs amongst loose gravel and cobbles in riffles and at the stream edge. Spawning sites are used by many fish, and up to 40 individuals can be found at once in areas smaller than 10 x 10 cm.
Scardinius erythrophthalmus (Linnaeus, 1758)
This member of the Cyprinidae family is native to Eurasia and was illegally imported to New Zealand in 1967. Stock bred from this importation was subsequently widely released and rudd are now well established in many North Island waterways, particularly in the Waikato River catchment. Rudd have also been recorded around Christchurch, and more recently from other parts of the South Island.
Like goldfish, rudd do not have any barbels around their mouth, a feature that tells them apart from koi. They can be distinguished from goldfish because they lack the stout spines on the front edge of the dorsal fin, and from orfe by the projections that occur at the bases of their pectoral and pelvis fins. Rudd can also be confused with perch, but perch have two dorsal fins, the first with several firm spines. Rudd are darker on their backs than on their bellies and have bronze highlights when the light catches their scales. Their fins are usually bright reddish orange.
Juvenile rudd are planktivorous, but as adults their diet consists mainly of aquatic plants. As a herbivore, rudd are likely to have a role in supressing the regeneration of aquatic plants in lakes and hence in maintaining poor water quality. A high-density rudd population ruined the trout fishery in an Auckland lake becuse they outcompeted trout for anglers lures. This suggests their introduction into new waters could be detrimental to fish and native plant communities as well as to water quality.
Like all the Cyprinidae, rudd are prolific breeders and large females can produce literally hundreds of thousands of eggs. The largest rudd ever recorded was over 400 mm in length, but fish 200–250 mm in size are much more common.
Anguilla australis (Richardson, 1841)
Shortfin eels are one of the three Anguillidae species found in New Zealand. They differ from longfin eels in the length of their dorsal fin. In shortfin eels, the dorsal and anal fins are the same length so the ends are almost adjacent when the fish is viewed side-on.
In longfin eels the dorsal fin is longer and extends well forward towards the head. Shortfin eels usually have a silvery belly compared to a yellowish one on longfins, but colours can vary considerably. Even pure yellow shortfin eels have been caught!
Shortfin eels are found throughout New Zealand and on Chatham and Stewart Island. However, they are not unique to this country and also occur throughout the South Pacific – in Australia, New Caledonia, Norfolk and Lord Howe Island, and perhaps Fiji. Generally shortfin eels are found at lower elevations and not as far inland as longfin eels, but they are still able to climb large obstacles such as waterfalls when they are young. They are often very numerous in lowland lakes, wetlands, and streams, and shortfin eels form the basis of the commercial eel fishery that has existed for over 20 years in New Zealand.
Shortfin eels are our most tolerant native fish species. They survive environmental hazards like high water temperatures or low dissolved oxygen concentrations. That means they can live in habitats where other species cannot survive. Their ability to live almost anywhere might explain why eels are so familiar to New Zealanders and why they were such an important food resource for Maori.
Galaxias postvectis (Clarke, 1899)
As its name implies, the shortjaw kokopu has an undercut jaw, with the lower jaw being shorter than the upper jaw. Koaro also have shortened lower jaws, but they are much more tube shaped than the kokopu. Shortjaw kokopu are also rather drab in colour unlike the sparkly koaro. The main distinguishing feature is a distinctive dark blotch on each side just behind the gills. Otherwise, this fish is essentially brownish with faint bands and blotches.
Shortjaw kokopu are endemic to New Zealand and do not occur on Stewart or Chatham Island. Although they penetrate well inland in many catchments, they appear to be restricted to streams with native forest vegetation. Even though it is widespread, the shortjaw kokopu is probably the rarest of the whitebait galaxiids as it is unusual to capture more than a few fish at a given site. It is usually found in streams with large boulders in pools and is difficult to catch using conventional methods. Because this fish has been so rarely encountered, little is known about its life history. In 2009, the first landlocked population was discovered in an Auckland reservoir.
Hypophthalmichthys molitrix (Valenciennes, 1844)
There are no self-sustaining populations of silver carp in New Zealand. Like grass carp, silver carp were brought to New Zealand specifically for their potential to control the growth of aquatic plants, in this case tiny floating plants known as phytoplankton. Field trials showed that silver carp could control planktonic blooms of bluegreen algae(cyanobacteria) at most times if enough fish were present. Cyanobacterial blooms are undesirable because they cause the water to become toxic and can cause the death of cattle and health problems for humans.
Silver carp have a distinctive bright silver colour and are unlikely to be confused with other fish species in New Zealand. They have small scales and no barbels. They feed by filtering phytoplankton from the water using specialised gill structures and their gut is greatly elongated to aid digestion of their food. Like grass carp, silver carp have very specific breeding and rearing requirements and it is unlikely that self-sustaining populations could develop in New Zealand rivers, although the risk of breeding in the Waikato River is much higher than in all other rivers. In North American rivers where they now breed and are common, they are reknowned for their jumping behaviour which creates a hazard for boaties.
Field trials with silver carp ceased in 1982. Since then brood stock have been transferred to and are maintained at a private hatchery north of Auckland. Their future in New Zealand is uncertain.
Oncorhynchus nerka (Walbaum, 1792)
Sockeye salmon stocks in New Zealand derive from a single importation of eggs that occurred in 1902. Although in their native North Pacific habitat most stocks are anadromous, stocks in New Zealand are wholly land-locked. Sockeye were released into the Waitaki River catchment, and were restricted to Lake Ohau for over 60 years where they were largely unknown to anglers. When Lake Benmore was established, this provided the sockeye with unusual but effective adult habitat, and during the 1970s stocks increased. However, when Ruataniwha Dam was completed in 1982, access to Lake Benmore was no longer possible, and today, apart from breeding populations on a couple of commercial salmon farms, sockeye salmon are virtually extinct.
Sockeye salmon co-exist in the Waitaki catchment with chinook salmon and brown and rainbow trout. The black gums of the chinook salmon distinguish this species from the sockeye. Sockeye also have a long-based anal fin (see glossary), which can be used to tell them apart from the trout species.
In North America, sockeye salmon support an important commercial fishery and are a splendid table fish with bright orange flesh. The land-locked stocks here do not grow as large as their anadromous northern counterparts and rarely exceed 1 kg in weight. Northern stocks also develop brilliant spawning colours, becoming bright red along the back and sides with a green head. These colours are much more subdued in the New Zealand stocks although a pink flush may develop along the sides of larger spawning fish. Spawning occurs in autumn and is confined to a brief period of 2–3 weeks.
Stokellia anisodon (Stokell, 1941)
Stokells smelt is the second of the two smelt species found in New Zealand. Although it superficially resembles the common smelt, it is sufficiently different, at least to biologists, to warrant a new generic name, Stokellia. This name honours G. Stokell, a biologist who collected and studied New Zealand’s freshwater fish for over 40 years, and who did much to identify and classify the species.
Stokells smelt has smaller scales than the common smelt, a feature that only an expert would recognise. The teeth, which are not a very obvious feature, are used to tell the two species apart. The small, fleshy, adipose fin can be used to distinguish smelt from galaxiids, however, smelt can be distinguished from the salmonids (which have an adipose fin) by the absence of a lateral line.
Found only on the east coast of the South Island between the Waiau and Waitaki Rivers, Stokells smelt is a strictly coastal species and is never found very far inland. In fact, this species probably spends most of its life in the marine environment. They enter fresh water to spawn in late spring and summer, and can be extremely abundant at times, providing a feast for the trout, kahawai, and sea birds that prey on the annual migrations. Stokells smelt grows to about 95 mm in length, but mature adults are typically 70–90 mm long.
Gobiomorphus alpinus (Stokell, 1962)
Although the Tarndale bully is hard to visually distinguish from the other bully species, its location is a dead giveaway. Found in only a few small sub-alpine tarns in the headwaters of the Clarence and Wairau Rivers, it lives in splendid isolation in this remote region of Marlborough. The bully’s name comes from its location - that part of Molesworth Station formerly known as Tarndale Station.
Tinca tinca (Linnaeus, 1758)
This member of the Cyprinidae family is native to Europe and was first introduced to New Zealand in 1867. Although imported as a sports fish, there has been little angler interest in tench until recently. Tench grow to a large size in New Zealand, and some northern lakes have now gained an international reputation among anglers who prefer fishing for coarse fish. Fish over 2 kg in weight are not uncommon, and in some instances 4-kg fish have been caught.
Tench are generally an olive green colour although this varies from dark to light. There is a single small barbel at each corner of the mouth. The fins tend to be thick and fleshy and the body is covered in small scales. Their eyes are bright orange, and this is their most distinctive characteristic.
The biology of tench in New Zealand has not been studied, but is probably similar to that of fish in their native waters. Tench generally live in still or slow-flowing waters and are carnivorous, feeding mainly on crustaceans, molluscs and insect larvae. Males have longer and fatter pelvic fins than females. Spawning occurs in spring and summer and, like all the Cyprinidae, tench are prolific breeders; a large female may produce hundreds of thousands of small eggs.
Although most fishing for tench occurs in the Auckland area, tench are also present in some lakes and ponds in Northland, Tauranga and Wellington. They have been present in the South Island near Oamaru for many years, but have also been found recently in Nelson, Marlborough and Canterbury during recent surveys by the Department of Conservation. A golden variety of tench, which is bright yellow-orange, is thought to be present in some small lakes and ponds near Auckland. This variety of tench was illegally imported in about 1980.
Cheimarrichthys fosteri (Haast, 1874)
This little fish is the only freshwater member of the Pinguipedidae family in New Zealand. Closely related to the more familiar blue cod, the scientific name of this fish means literally torrent (cheimarros) fish (ichthyos). And it’s an apt name for this species because that is exactly where this fish lives - right in the swift white rapids of stony rivers and streams. The flattened head and large pectoral fins help this fish to anchor on the riverbed, while the raised eyes and ventral mouth are probably adaptations for feeding in this habitat. These later two features, along with the distinct dark bands along the sides, easily distinguish the torrentfish from other freshwater species.
Despite its skill at living in swift water, the torrentfish is not a good climber and only penetrates inland in river systems where the gradient is relatively low. It is less common in Otago and Southland than in other parts of New Zealand, and torrentfish have never been reported from Fiordland, Stewart, or Chatham Islands. It is not found in any other country except New Zealand.
Like many of New Zealand’s freshwater fish, the torrentfish undertakes migrations between the sea and fresh water as part of its life cycle. Looking just like tiny replicas of the adults, juvenile torrentfish enter fresh water in spring and autumn, and after a few weeks in the estuaries, begin moving upstream to the adult habitat. The adults continue to move slowly upstream, with the largest and most inland fish being the females and those in the lower reaches predominately males. How and where they get together for spawning is unknown - we suspect the females move downstream to the males, but no spawning sites or spawning behaviour has ever been observed. Despite the mystery surrounding aspects of its life cycle, torrentfish are one of the most common fish in open-bedded rivers in New Zealand.
Gobiomorphus breviceps (Stokell, 1940)
The upland bully is one of the non-diadromous members of the Eleotridae family. That means they live their whole lives in fresh water. Adult male upland bullies are relatively easy to identify - they have orange spots on their cheeks and head, and the outer edge of the dorsal fin is also orange. Immature fish and females are less easy to identify, particularly where their distribution overlaps with Crans bully in the lower North Island. Experts have to rely on pectoral fin ray counts under a microscope to ensure that upland bullies can be distinguishd from Crans bullies.
Upland bullies are common along the east coast of the South Island. On the west coast, they occur in the Hokitika, Grey, and Buller River systems, but are absent from rivers north and south of there. It was recorded for the first time on Stewart Island in 1998. In the North Island, upland bullies are found from the Ruamahanga River catchment up to the Wanganui and Patea systems. They do not occur in the northern half of the North Island.
Because upland bullies do not have to go to sea as part of their life cycle, they occur well inland in many river systems. But they are also found close to the coast. They will tolerate a variety of habitats, from stony-bedded rivers to weedy streams, and have even established populations in a few South Island lakes, e.g. Lake Coleridge.
Like all the bully species, the males establish and defend territories during the breeding season. This accounts for their more dramatic colouration compared to the females. The eggs are laid in a primitive nest, which is usually the underside of a large rock. However, instream debris such as wood can also be used. After the eggs are laid, the male guards the nest from intruders and fans the eggs to keep them oxygenated. There is no parental care after hatching.
Galaxias prognathus (Stokell, 1940)
As its name implies, the distinguishing characteristic of this member of the Galaxiidae family is its long, protruding jaw. In fact, its Latin name means exactly that – forward (pro) jaw (gnathos). The long, protruding jaw of the longjaw galaxias is unmistakable, and it is unlikely to be confused with any other species except the lowland longjaw, which has only 5 (compared to 7) pelvic fin rays. The longjaw galaxias is a slender, elongate fish and is one of the smaller galaxiids, rarely exceeding 80 mm in length.
The longjaw galaxias is non-diadromous, and the whole life cycle takes place in fresh water. Spawning occurs from March to May and also from October to November. They are nocturnal feeders and live on a variety of aquatic insects, especially mayflies. Studies of their diets showed that they selected soft-bodied prey in preference to harder shelled animals like snails or cased-caddis.
Longjaw galaxias generally live at mid to high altitudes in rivers and streams draining to the east coast of the South Island. Like the Canterbury and alpine galaxias, a population also occurs in the headwaters of the Buller River (Maruia River) near Lewis Pass. Although it inhabits swiftly flowing streams, longjaw galaxias are usually found along the quiet river margins.
Aldrichetta forsteri (Valenciennes, 1836)
There are two members of the Mugilidae (or mullet) family in New Zealand, the yelloweyed mullet and the grey mullet. The mullet family has a worldwide distribution in rivers and seas of all regions except the Arctic and Antarctic Oceans, with about 70 species in total. The two species found in New Zealand are not really freshwater fish, but both are common in river estuaries and they can penetrate upstream for several kilometres in large rivers.
All mullets have two dorsal fins, and the first one is tall with four obvious spines. They also have large, easily dislodged scales. New Zealand mullets belong in two separate genera based on the presence of an adipose eyelid. This is a thick fleshy eyelid that forms an oval, vertical slit over the pupil on the grey mullet. For amateurs, however, the bright yellow eye of the appropriately named yelloweyed mullet is probably the easiest way to distinguish the two species.
Yelloweyed mullet occur all around New Zealand and they are also found in western and eastern Australia. They are never found far from the coast. Yelloweyed mullet are very familiar to any youngster who has spent time fishing off wharves or in harbours, competing with the spotty as the most easily caught fish. Fish 150–200 mm long are commonly caught, although fish of up to 500 mm have been reported. Yelloweyed mullet may spend considerable time in fresh water, for example they are found at all times of the year in Lake Ellesmere south of Christchurch, but their spawning takes place in the sea.