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Fish Schools

Fish Schools Photo Credit: Clipart.com

Making fish hatcheries more mentally stimulating may increase the fish's chance of survival in the wild.


Transcript

Schools for fish. I'm Bob Hirshon and this is Science Update.

Imagine growing up in an empty room, and not being let out until adulthood. That's like the experience of fish bred in hatcheries and released into the wild. But recently, at a salmon hatchery in Norway, Penn State University biologist Victoria Braithwaite and her colleagues spruced up the empty tanks. 

They added rocks, plants, and other obstacles, and moved and replaced them periodically. After eight weeks, the fish competed with conventionally raised salmon in a maze.

Braithwaite:
The fish that had had the enrichment items, unlike those that were reared in standard conditions, were just much more efficient in getting out of the maze.

Changes in the fish's brain also indicated a higher capacity for learning and memory. Braithwaite says that if hatcheries can raise smarter fish, they may be able to breed fewer of them, since they'd be more likely to survive in the wild. I'm Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

Overfishing, pollution, climate change, and other factors have seriously threatened many fish populations, including species that humans rely on for food. One way that conservationists are fighting against the loss is by raising fish, like salmon, in hatcheries (captive breeding centers), and then releasing them into the wild. 

It's assumed that many of these fish won't survive to reproduce. After all, predators, disease, and environmental pressures claim the lives of many wild fish. However, it's reasonable to expect that captive-raised fish would have a lower chance of survival than wild fish, simply because they're being introduced into a new and more dangerous environment that they haven't learned to live in. (This is a potential problem with almost any animal raised in captivity and released into the wild.)

In this study, the researchers created a more stimulating and realistic captive environment for the hatchery fish, and studied its effects on the fish's performance in solving a maze. They found that when the fish were raised in tanks that had the types of objects they'd encounter in nature, like rocks and plants, they did become more adept at the mazes. The fish's brains also showed signs of being more developed in the areas of learning and memory.

This doesn't prove that the fish will actually survive better in the wild. That's actually the next step of the research. Braithwaite and her colleagues will raise some fish in typical, empty tanks and others in enhanced tanks, and tag them before they're released so that they can be tracked. Salmon eventually return to where they were hatched, so the researchers will be able to count how many of the fish-school graduates return, compared with typical hatchery fish.

Eventually, the hope is to make hatcheries more efficient. If enhancing the tanks makes the fish better able to survive, then hatcheries may be able to get the same results they're getting now by starting with far fewer fish. This may also make fish hatcheries economically viable in places where they currently aren't.

Now try and answer these questions:

  1. What is the purpose of a fish hatchery?
  2. Why might hatchery fish not survive as well in the wild?
  3. What effects did the enhanced environment have on the fish? How might this impact their survival?
  4. Why is further study needed to know whether the fish raised in enhanced tanks will survive better than fish raised in empty tanks?

You may want to check out the August 16, 2013, Science Update Podcast to hear further information about this Science Update and the other programs for that week.This podcast's topics include: Scientists test a 3-D underwater microscope, how oxygen led to the rise of ocean carnivores, and why some fish are going back to school. Also, can computers be funny?

The Science Update Disappearing Fish highlights some of the fish species currently in jeopardy.

Ever declining numbers of marine plants and fish are sending ecologists scrambling for better ways to protect the oceans. Some have suggested that marine reserves are the answer. The Science Update Marine Reserves looks at the unexpected impact marine reserves have on their surroundings.


Going Further


For Educators

In the Science NetLinks lesson The Fish Trade, students examine the interdependence of global trade in the context of the economic and social aspects of fisheries and aquaculture.

The Science Update Disappearing Fish highlights some of the fish species currently in jeopardy.

Ever declining numbers of marine plants and fish are sending ecologists scrambling for better ways to protect the oceans. Some have suggested that marine reserves are the answer. The Science Update Marine Reserves looks at the unexpected impact marine reserves have on their surroundings.


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