ANGFA Queensland

Conservation fish hatcheries are good at rearing lots of fish, but their survivability rate is low. Victoria Braithwaite, professor of fisheries and biology, Penn State, said that adding objects to make hatchery tanks more stimulating for the fish can make fish smarter and better adapted to survive in the wild. Photo: Anne Gro Salvanes

Media release from Penn State at EurekAlert!

Raising fish in tanks that contain hiding places and other obstacles can make the fish both smarter and improve their chances of survival when they are released into the wild, according to an international team of researchers.

"It's a key problem in that we are very good at rearing fish, but we're really not very good at releasing those animals in the wild such that they survive," said Victoria Braithwaite, professor of fisheries and biology, Penn State. "There's a mismatch between the way we raise them and the real world."

Juvenile Atlantic salmon raised in tanks that including pebble and rock hiding places and floating artificial plants were better able to navigate mazes and showed signs of improved brain function compared to the salmon reared in standard hatchery tanks, Braithwaite said. This may help conservation fish hatcheries raise and release fish that are better adapted to survive in the wild.

Setting up an aquatic playground with rocks and artificial plants in a fish hatchery tank made fish smarter, according to Victoria Braithwaite, professor of fisheries and biology. Researchers discovered when fish were raised in the enriched tank, parts of their brains changed and they could escape from a maze quicker than fish raised in standard tanks. Photo: Anne Gro Salvanes

Conservation fish hatcheries raise cod, salmon, trout and other types of fish and release them in places where their species may be threatened, or where their populations are declining.

"The philosophy of most fish hatcheries is to rear a large number of fish and hope some survive," said Braithwaite. "What this study is suggesting is that you could raise fewer, but smarter fish, and you will still have higher survivability once you release them."

The researchers, who released their findings today (July 31) in the Proceedings of the Royal Society B, placed pebbles and rocks at the bottom of the tank and added plastic plants weighted down so they would float vertically in the water. Braithwaite said the objects created a more natural, three-dimensional ecosystem.

"In the hatchery the world is homogenous, life is boring and monotonous," Braithwaite said. "The water flow is the same, you don't have to find your food and you don't have to avoid predators."

The researchers also moved the objects around about once a week during the eight-week study, which took place in Norway.

When the researchers placed the salmon in a maze, the fish raised in the enriched tanks made fewer mistakes when trying to escape the maze, Braithwaite said. The performance of the salmon from the enriched tank continued to improve with each trial, and they learned to solve the maze much faster than fish reared the standard way.

Juvenile Atlantic salmon raised in tanks with hiding places and floating artificial plants showed signs of improved brain function and could better navigate mazes than the salmon reared in standard hatchery tanks. The discovery may help fish hatcheries raise a smaller number of fish that can better survive in the wild. Photo: Anne Gro Salvanes

The brains of the fish from the enriched tank were also different from the fish raised in the standard hatchery tanks, according to the researchers.

They noted increased expressions of a gene in a region of the fish's brain that is associated with learning and memory, an indication of increased brain function and growth. The fish raised in standard tanks did not show this sign of increased brain development.

Interacting with the environment can influence gene expression in the brain, Braithwaite said.

"The brain is a very plastic organ, it's a dynamic structure," said Braithwaite, who worked with Ann Gro Vea Salvanes, professor of biology; Olav

Moberg, doctoral student; Tome Ole Nilsen, researcher in marine development biology; Knut Helge Jensen, senior engineer in evolutionary ecology, all at the University of Bergen, Norway; and Lars O.E. Ebbesson, group leader of integrative fish biology, Uni Research, Bergen. Braithwaite said the enriched tanks created significant improvement in the intelligence and adaptability of the fish, but were relatively inexpensive and easy to implement. Owners of fish hatcheries should be able to afford the creation of enhanced tanks.

Original story from Australia Network News at the ABC

A bigeye tuna that was first tagged by a fisherman 13 years ago has been recaptured off the coast of Fiji.

Pacific tuna tagging program. Teams catch and release thousands of tuna after fitting them with a numbered plastic tag and recording their species, size, condition, tagging date and location. Photo: Secretariat of the Pacific Community

The 100 kilogram tuna has been labelled the 'grand daddy' of the Pacific tuna tagging program, which has been running since the 1970s.

Bruno Leroy from the Secretariat of the Pacific Community says the tuna was originally tagged by a Tongan fisherman in October 2000.

"The fish has been recaptured very close to its original position, 13 years later," he said.

"Of course we don't know where it's been during all this time, but it's suggesting that this particular species [might have] some sort of homing behaviour.

"Some other recapture data from big-eye tuna also suggests that the older the tuna is, the less its moving."

The Secretariat of the Pacific Community uses trained teams catch and release thousands of tuna after fitting them with a numbered plastic tag and recording their species, size, condition, tagging date and location.

Bruno Leroy says the tagging program is a vital part of efforts to maintain the health and sustainability of tuna fisheries in the Pacific.

"When you tag tuna, you can learn about fish movement, migration and the fish world," he said.

"The main goal is to estimate what proportion of the fish stock is taken by the fishing industry, which, in the western and central Pacific Ocean, is the biggest tuna fishery in the world.

"We are talking about 2.4 million tonnes every year...[so tagging] gives you an idea of the pressure on the stock - if this is sustainable or not."

Original story by Matthew Cawood, The Land

A RECENT calculation that global fish farming now produces more tonnage than beef farming highlights a little-considered reality: when it comes to feeding the world's growing population, the sea may be more important than the land.

A Queensland prawn farm. Photo: CSIRO

Nigel Preston certainly thinks so. The acting director of CSIRO's Food Futures Flagship, Dr Preston observes that only a third of the planet is dry land; the remainder is water.

"Where are we going to meet the demand for animal protein? Do the sums," Dr Preston said.

The US-based Earth Policy Institute recently did the sums on fish versus beef. Somewhere in 2011, the Institute said, the world began producing more farmed fish than beef.

In 2012, aquaculture produced 66 million tonnes of protein, and the beef industry 63 million tonnes.

Aquaculture is now the world's fastest growing animal protein food. The Institute reported that production of farmed fish is growing by nearly six per cent a year, poultry by 4pc, and pork by 1.7pc — "fast outpacing beef, which barely increased at all".

Dr Preston thinks the aquaculture industry's growth will continue to climb, thanks to fundamentals no longer available to land-based agriculture.

To begin with, some of aquaculture's livestock are among the world's most efficient convertors of feedstuff to animal protein.

A Black Tiger Prawn, one of CSIRO’s ‘perfect’ prawns. Photo: CSIRO

To produce 100 grams of beef requires about 800 grams of feed, giving cattle a feed conversion ratio (FCR) of about 8.0. Pork has an FCR reported as between 3.5-5.0, poultry 1.9.

Farmed Atlantic salmon, the most efficient of aquaculture's livestock, have an FCR of about 1.2 - meaning 120 grams of feed can produce 100 grams of salmon. In some cases, farmed salmon have reached an FCR of 1.0. On the other hand, farmed tuna can have an FCR of 10-20.

These figures aren't set in stone: aquaculture has enormous scope to improve productivity through breeding alone.

Aquaculture's livestock have barely been touched by selective breeding. It is akin to today's wheat yields being obtained by a variety only a generation or two removed from the original wheat ancestor.

Agricultural livestock have been developed through millennia of intuitive selection based on appearance and fitness for a location. That long, arduous process is being bypassed by CSIRO, which is instead cashing in on the molecular DNA technologies recently developed for animals like cattle and goats - with phenomenal results.

Within eight generations, CSIRO researchers boosted yields of the black tiger prawn from the industry average of five tonnes per hectare to 17.5 t/ha. In prawn-time, eight generations is eight years.

For aquaculture producers, such rapid development sometimes outstrips their ability to handle it, Dr Preston said. A system with the technology to handle 5t/ha is severely stressed when a new prawn suddenly bulges capacity at 17t/ha.

In prawns, and salmon, Dr Preston reported that breeding is continuing to improve productivity by about 10 per cent each generation.

The ultimate testimony to fish productivity rests in Asian villages, where centuries of necessity have honed peasant productivity to a fine edge.

Here, herbivorous fish are grown in ponds "with much higher production efficiency than you can with chickens or pigs," Dr Preston said.

"There are a number of reasons, for that, not least that a pond is three-dimensional. If you put chickens in it, they would just utilise the floor. Fill it up with water, and fish can utilise the whole production space."

Australia is not constrained for production space, Dr Preston observes, at least in saltwater. Australia's variable freshwater flows make freshwater aquaculture a dicier proposition.

In northern Australia, there are extensive tracts of coastline unsuitable for any other form of production, but highly suited to aquaculture.

"If you dig some ponds, you can have a very high value, high production protein system, and do it in a way that has no adverse impacts on the receiving environment," Dr Preston said.

"It's probably not something you can say about any terrestrial form of agriculture."

"We've shown over the past 20 years that prawn farms adjacent to the Great Barrier Reef have absolutely no adverse impacts. If you were to stop growing prawns and released the water into the environment, and went back three months later, using the most sensitive detection techniques available, you couldn't tell that there had been a discharge of water into the reef."

At the moment, Australians export $7.5 billion of excess meat and dairy each year, but we import 60 per cent of our seafood. Dr Preston thinks there is something wrong with this equation.

"Will it change? Absolutely, it will."