‘Do fish talk?’ and other important questions:
A mysterious fish ‘language’ is being uncovered at a New Zealand marine reserve, leading to startling hypotheses about fish communication.
NZ Marine Sciences Society conference on the latest in marine research.
Underwater recordings of grunts, growls, chirps and pops at Leigh Marine Reserve, north of Auckland, have lead scientists to suspect fish use sound for a variety of functions including social interactions, interception and orientation – much like whales.
The research is just one of 178 research papers to be presented at the NZ Marine Sciences Society conference, 7-9 July: Marine Environments – Past, Present, Future.
In another paper, University of Otago scientists have been able to follow how Kaikoura’s sperm whales dive in 3D for the first time. Sonar recordings have revealed foraging habits including swooping down on prey from above, chasing prey in midwater depths (400m), and foraging along the canyon floor at depths of over 900 metres – nine football fields deep.
National Institute of Water and Atmospheric Research (NIWA) scientist Alison MacDiarmid, who is chair of the conference organising committee, says the conference was an opportunity for researchers – and the public – to get an update on the work going on around the country.
“We are at a confluence of change,” said Dr MacDiarmid. “The marine economy is growing and with government encouragement it is likely to grow further. This increases pressure on the use of marine space and on environmental limits that, once exceeded, could undermine the marine economy. We need to ensure that sufficient science is underway that can help document, explore, explain and suggest just how our marine ecosystems have responded, are responding and will respond to a plethora of impacts ranging from one-off and local to long-term and widespread.”
Topics covered in the 178 research papers include
· How effective are Marine Reserves?
· The habitats of mega predators, from the tagging of Great White sharks, to the impacts of humans and tourism on the habitats and behaviour of dolphins. How effective are Hector’s Dolphin protection measures?
· Modelling of tidal energy projects: what works, and what are their effect on the tidal currents and the surrounding environment?
· The Sustainability of New Zealand fishing resources such as Orange Roughy, Hoki, and Groper
· Industry-related research –the impact of exercise on fish growth, threats to the Greenshell mussel industry, causes of growth retardation in Salmon, and the spread of the bryozoan organisms that foul boats and harbours
· The effect of climate change on a particular marine species and an analysis of lake sediment to measure climate change over the last 7,000 years
The conference marks the 50th anniversary of the NZ Marine Sciences Society, set up in May 1960.
Research topics that may be of further interest:
Auckland University marine scientist Shahriman Ghazali has been listening to underwater recordings at Leigh Marine Reserve, trying to decipher who’s making the grunts, growls, chirps and pops - and what they mean.
By placing the fish into tanks and coaxing them to continue vocalising (noise made by vibrating their swim bladder) he is working to identify which fish make which sound and why.
Fish vocalisation has been researched overseas, but little has been done in New Zealand. Unlike the ability to hear which is inclusive in fish, the ability to vocalize on the other hand appears selective. Mr Ghazali and his supervisors John Montgomery, Andrew Jeffs and Craig Radford have discovered the gurnard has a wide vocal repertoire. Furthermore, noises audible to humans that divers have for years attributed to crayfish, seem to be made by the nocturnal plantivorous fish the bigeye (Pempheris adspersa), which lives in similar crevices.
The team say the vocalisation sounds suggest these fish use sound for a variety of functions including communication in social interactions. They are also measuring how the sounds propagate away from the reef to work out if fish use the sound waves for ‘acoustic orientation’.
And for those who are wondering: Goldfish don’t make any noise, but they have exceptional hearing.
Some of Mr Ghazali’s audio recordings are available on request
Reconstructing Past Marine Environments through Archaeology
Archaeologists, in collaboration with NIWA scientists, have been working to estimate how much kaimoana was harvested by pre-European Maori, to paint a picture of the effect of pre-European Maori on the marine environment – and hopefully draw lessons about the changing marinescape.
Focussing on two areas, Otago and Hauraki Gulf, University of Otago Associate Professor Ian Smith examined information from all the excavations of the area to create a picture of how many animals were harvested in those two areas at 1400 AD and again at 1750 AD.
Through studies of human bones found at the time, scientists have been able to estimate what proportion of plants and animals made up local diets. By estimating human populations at the time, they have been able to estimate how many tonnes of snapper, spotted shags, pipi, seals and other marine animals were harvested.
Impacts were greater in the north than south, due to higher human populations, leading to extinction of furseals and sea lions in the North Island, but overall Maori harvesting had minimal impact on the marine environment when compared to the more recent past. In conjunction with evidence for climate change the research will help draw a picture of the marine environment in the past and how it has adapted over time.
3D underwater movements of sperm whales in the Kaikoura Canyon
Otago University scientists have developed a sonar system, similar to those used to listen for submarines, to collect the first 3-D information about what Kaikoura’s sperm whales do when they dive deep underwater.
Up until now, most tracking of sperm whales has been via electronic tagging, which measures sounds, depths and orientation, but no other sense of direction.
PhD candidate Brian Miller and his supervisor Associate Professor Steve Dawson used four underwater-listening buoys, or sonobuoys, to measure where the whales went. Sonobuoys are usually used to detect submarines and were neither affordable nor available in New Zealand, so the scientists made their own and created software to track the whales in 3-D.
Brian then spent a year living in Kaikoura waiting for fine weather so he could head out in his 6-metre boat and place the four buoys so that the whales would swim within the one square mile area. “Sperm whales are very, very vocal, they make echolocation clicks almost all the time,” he said. “As they get closer to their prey, their long-range echolocation sounds become a ‘creak’ or ‘buzz’ so we could tell when they were close to their prey.”
Whale movements before and after the creak revealed a variety of foraging strategies including swooping down on prey from above, chasing prey in midwater depths, and foraging along the canyon floor at depths of over 900 metres.
Mr Miller also discovered these 13-15m long giants, known to hunt alone, also dive remarkably close to each other. "On one occasion, they may have got as close as a whale-length apart, but so far there is little indication of co-operative behaviour", he said.
Audio and video images are available upon request.
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