Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search


How butterfish "buck the system"

7 March 2005

University of Auckland research aims to find out how butterfish "buck the system"

Finding out how New Zealand butterfish "buck the system" is the aim of a study by researchers at The University of Auckland's School of Biological Sciences in the Faculty of Science.

Dr David Raubenheimer, a nutritional ecologist, and Dr Kendall Clements, an expert on marine herbivorous fishes, are the recipients of a Marsden Fund grant to investigate the foraging and nutrient intake of wild and captive butterfish.

Their research aims to find out how butterfish, also known as green-bone, defy conventional thinking that cold-blooded, herbivorous fish only thrive in warm, ocean environments.

Like cows, many seaweed-eating fishes employ symbioses with micro-organisms in the gut to ferment plant foods and extract the nutrients.

"Butterfish are cold-blooded, live in cold water and feed mainly on kelp. There's the general belief that these animals should not be able to meet their nutritional needs from these plants because the microbes needed to break them down require a relatively high temperature to function," says Dr Raubenheimer.

"But not only do butterfish survive here, flying in the face of received dogma, they also grow bigger and are at higher population densities the further south you go and the colder the water becomes. We aim to find out how they buck the system."

The butterfish is found in shallow water around the coasts of New Zealand and its offshore islands where it feeds largely on kelp. It is caught in small commercial quantities by set net, mainly in the Cook Strait. It is most plentiful around Stewart Island and lives up to at least 25 years of age. At the Three Kings Islands off Cape Reinga the butterfish is replaced by the closely-related blue-finned butterfish, Odax cyanoallix.

While the project is primarily aimed at better understanding of the nutritional biology of the butterfish and furthering knowledge about biological systems, Dr Raubenheimer says there are potential implications for commercial fish farming.

"The oceans are pretty stretched at the moment in terms of how sustainable fishing is as an industry, so the alternative is aquaculture. The problem with most fish aquaculture is that carnivorous fish are farmed, which means they are fed basically on fish meal further depleting the ocean's resources.

"But the butterfish is an edible, herbivorous fish which could be farmed much more efficiently and sustainably. It would be hopelessly inefficient for our pastoral farmers to farm carnivores, but we do it all the time with fish."

Dr Clements says the project is a "marriage" of his and Dr Raubenheimer's expertise. Dr Raubenheimer joined the Faculty of Science's School of Biological Sciences earlier this year from Oxford University. Professor Howard Choat from James Cook University, Queensland, is also a collaborator on the project.

"I've worked for nearly 20 years on the biology of these fish. We have a good idea of what they eat and how they digest it. But with this grant, we are looking not so much from a microbiological viewpoint as we have done previously, instead we are bringing in David's expertise as a world authority on how animals organise their nutrient budgets.

"Herbivorous fish sit at the base of the food chain, they feed on plants which are primary producers and almost nothing is known about the way seaweed is converted into fish flesh. We don't know what the processes are, why fish eat some seaweed and not others. At a simplistic level, this would be a huge advantage in terms of aquaculture. But these fish occur naturally on our reefs and if we want to understand the way our reef ecosystems function, then it is important to know about these things."

Using theoretical modeling techniques that Dr Raubenheimer has developed to study nutrition in insects and other animals, the research will examine food selection patterns of the butterfish in the wild in northern, central and southern New Zealand, and analyse the chemical composition of the nutrients gained. Dr Raubenheimer has recently used the same modeling techniques to derive a new theory for the relationship between food selection and the global increase in obesity and obesity-related diseases in humans.

In the laboratory, the chemical composition of nutrients will be manipulated to analyse selection patterns of captive fish. Field and laboratory outcomes will be compared to get "a very strong approach for reading the nutritional foraging and processing" of these fish, say the researchers.

The study will also look at growth patterns in each marine region to determine where the butterfish does best and if water temperature has an effect on their growth and at what stage of their life cycle.


© Scoop Media

Business Headlines | Sci-Tech Headlines


I Sing The Highway Electric: Charge Net NZ To Connect New Zealand

BMW is turning Middle Earth electric after today announcing a substantial contribution to the charging network Charge Net NZ. This landmark partnership will enable Kiwis to drive their electric vehicles (EVs) right across New Zealand through the installation of a fast charging highway stretching from Kaitaia to Invercargill. More>>


Watch This Space: Mahia Rocket Lab Launch Site Officially Opened

Economic Development Minster Steven Joyce today opened New Zealand’s first orbital launch site, Rocket Lab Launch Complex 1, on the Mahia Peninsula on the North Island’s east coast. More>>


Marketing Rocks!
Ig Nobel Award Winners Assess The Personality Of Rocks

A Massey University marketing lecturer has received the 2016 Ig Nobel Prize for economics for a research project that asked university students to describe the “brand personalities” of three rocks. More>>


Nurofen Promotion: Reckitt Benckiser To Plead Guilty To Misleading Ads

Reckitt Benckiser (New Zealand) intends to plead guilty to charges of misleading consumers over the way it promoted a range of Nurofen products, the Commerce Commission says. More>>


Half A Billion Accounts, Including Xtra: Yahoo Confirms Huge Data Breach

The account information may have included names, email addresses, telephone numbers, dates of birth, hashed passwords (the vast majority with bcrypt) and, in some cases, encrypted or unencrypted security questions and answers. More>>


Rural Branches: Westpac To Close 19 Branches, ANZ Looks At 7

Westpac confirms it will close nineteen branches across the country; ANZ closes its Ngaruawahia branch and is consulting on plans to close six more branches; The bank workers union says many of its members are nervous about their futures and asking ... More>>

Interest Rates: RBNZ's Wheeler Keeps OCR At 2%

Reserve Bank governor Graeme Wheeler kept the official cash rate at 2 percent and said more easing will be needed to get inflation back within the target band. More>>


Get More From Scoop

Search Scoop  
Powered by Vodafone
NZ independent news