Freshwater fish

Latest news

A 3D Printer is helping save New Zealand’s endangered native fish

Media Release
14 November 2023
A 3D Printer is helping save New Zealand’s endangered native fish

NIWA’s freshwater ecologists helping regional councils remove the barriers to fish migration

21 June 2023
About 76 per cent of indigenous freshwater fish species, that’s 39 out of 54, are threatened with extinction or at risk of becoming threatened.

Half of NZ’s rivers blocked for migratory fish

Media Release
25 January 2023
Nearly half of New Zealand’s river network is partially or fully inaccessible to migratory fish, a new study shows.

Taonga Species Series: Īnanga

Feature story
14 September 2021
What does science tell us about New Zealands' migratory galaxiids?
 

Latest videos

2020_03_06_Alvin Setiawan_RAS

How to farm fish on land

About RAS

Recirculating aquaculture systems (RAS) are a land-based production technology for aquatic organisms and high-value finfish. They utilise simple water treatment technologies (mechanical and biological filtrations) to minimise water use and maintain a tightly controlled environment. These can range from very open systems that use only basic treatment technologies to reuse some of their water resource, to fully closed systems which reuse 100% of the water and only add new water to account for splashing and evaporation. RAS vary in their design and functionality depending on the species being produced, the local conditions and the cost/access to a local water resource.

Advantages of using RAS

  • Reduced water requirements 
  • Water is treated and recirculated, significantly reducing water requirements. 
  • Production Control
  • Water can be heated/cooled, high oxygen can be maintained, pH adjusted, pathogens treated, and waste products removed to maximise health, growth rates, and the welfare of the stock. 
  • Increase in long-term production
  • Stock are unaffected by seasonality, periodic disease events and adverse weather, allowing continuous and reliable production.  
  • Reduced environmental footprint
  • Waste streams are treated and recycled to ensure they have the least impact on the environment as possible. Being land-based, there is also no risk of fish escaping and interbreeding with wild populations. 
  • Flexible design
  • The system can easily be customised for different species, locations and consumer preferences. 
The world's most mysterious fish

The world's most mysterious fish

A video about The world's most mysterious fish. NIWA researchers are working with iwi to try to unlock the secrets of New Zealand tuna—freshwater eels. Every year tiny, glass eels wash in on the tide at river mouths along our coast. But where do they come from and how do they get there?

 

Freshwater fish swim their all for science

Freshwater fish swim their all for science

The tiny inanga have been plucked from Waikato streams and held in a darkened laboratory for the last month, undertaking highly advanced testing to find the strongest, fittest and fastest fish.

NIWA freshwater fish scientists are trying to understand how long they can swim at given speeds – between rests - and how much variation there is between fish of the same species.

 

A 3D Printer is helping save New Zealand’s endangered native fish

Media Release
14 November 2023
A 3D Printer is helping save New Zealand’s endangered native fish

NIWA’s freshwater ecologists helping regional councils remove the barriers to fish migration

21 June 2023
About 76 per cent of indigenous freshwater fish species, that’s 39 out of 54, are threatened with extinction or at risk of becoming threatened.

Game on

Have you ever heard of a fish climbing competition? Mia Blyth drops in on the native fish getting put through their paces for a very good cause.

Half of NZ’s rivers blocked for migratory fish

Media Release
25 January 2023
Nearly half of New Zealand’s river network is partially or fully inaccessible to migratory fish, a new study shows.

Taonga Species Series: Īnanga

Feature story
14 September 2021
What does science tell us about New Zealands' migratory galaxiids?
2020_03_06_Alvin Setiawan_RAS

How to farm fish on land

About RAS

Recirculating aquaculture systems (RAS) are a land-based production technology for aquatic organisms and high-value finfish. They utilise simple water treatment technologies (mechanical and biological filtrations) to minimise water use and maintain a tightly controlled environment. These can range from very open systems that use only basic treatment technologies to reuse some of their water resource, to fully closed systems which reuse 100% of the water and only add new water to account for splashing and evaporation. RAS vary in their design and functionality depending on the species being produced, the local conditions and the cost/access to a local water resource.

Advantages of using RAS

  • Reduced water requirements 
  • Water is treated and recirculated, significantly reducing water requirements. 
  • Production Control
  • Water can be heated/cooled, high oxygen can be maintained, pH adjusted, pathogens treated, and waste products removed to maximise health, growth rates, and the welfare of the stock. 
  • Increase in long-term production
  • Stock are unaffected by seasonality, periodic disease events and adverse weather, allowing continuous and reliable production.  
  • Reduced environmental footprint
  • Waste streams are treated and recycled to ensure they have the least impact on the environment as possible. Being land-based, there is also no risk of fish escaping and interbreeding with wild populations. 
  • Flexible design
  • The system can easily be customised for different species, locations and consumer preferences. 

Freshwater species show vulnerability to climate change

Media Release
15 September 2020
A new study has identified seven freshwater species native to Aotearoa-New Zealand that will likely be highly or very highly vulnerable to climate change.

Freshwater species - publications

These are some recent publications related to the freshwater species ecology and management programme.

Freshwater species ecology and management

The abundance and diversity of life in our rivers, lakes and estuaries is the ultimate indicator of the health and wellbeing of our aquatic ecosystems. NIWA is helping to ensure that New Zealand’s unique and iconic freshwater species are healthy, abundant and thriving.

Taonga Species Series: Tuna

Feature story
18 June 2020
What does science tell us about New Zealand eels?

Taonga Species Series

NIWA, through the MBIE-funded Cultural Keystone Species programme (2016-2020), have developed a series of iwi engagement booklets sharing science knowledge to support species management strategy.
The world's most mysterious fish

The world's most mysterious fish

A video about The world's most mysterious fish. NIWA researchers are working with iwi to try to unlock the secrets of New Zealand tuna—freshwater eels. Every year tiny, glass eels wash in on the tide at river mouths along our coast. But where do they come from and how do they get there?

 

Unlocking the mysterious marine life of eels

Feature story
1 February 2020
Tiny, translucent eels may hold the answers to one of the fish world’s great mysteries. Zen Gregor investigates.

Scientists help lamprey to spread the love

Media Release
30 September 2019
Contraptions that resemble upside-down kitchen sinks have been placed in the Waikawa River in Southland to attract a notoriously elusive native fish species.

Scientists study eels by moonlight

Media Release
1 August 2019
Under the light of the moon where the river meets the sea, NIWA researchers are planning to catch tiny fish that are all but invisible to the naked eye.

Scientists hoping to solve great eel mystery

Media Release
16 May 2019
NIWA freshwater scientists are pinning their hopes of solving an age-old mystery on 10 female longfin eels who are about to begin an epic journey to their spawning grounds somewhere in the Pacific Ocean.
Freshwater fish swim their all for science

Freshwater fish swim their all for science

The tiny inanga have been plucked from Waikato streams and held in a darkened laboratory for the last month, undertaking highly advanced testing to find the strongest, fittest and fastest fish.

NIWA freshwater fish scientists are trying to understand how long they can swim at given speeds – between rests - and how much variation there is between fish of the same species.

Freshwater fish swim their all for science

Media Release
26 March 2019
In a secret training location on the outskirts of Hamilton, a squad of whitebait is being put through its paces by fish scientists.

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All staff working on this subject

Dr Arnaud Gruss

Fisheries Population Modeller
Email Dr Arnaud Gruss
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Dr Michele Melchior

Freshwater Fish Ecologist
Email Dr Michele Melchior
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