Agriculture and Environment: Salmon

Better Management Practices: Reduce Escapes

Escapes can have a huge impact on wild salmon populations, particularly where those populations have been depressed.

For example, if a river has a salmon run of 5,000 animals a year, then a 5% level of escapes within that run (say 25 animals) would not be a large impact.


If, however, a river only has 25 animals in its annual run, then the 25 escapes would have a much larger impact. To date, there is no science available to define what impact levels would be "acceptable" for what reasons.

Similarly, moving the industry away from the mouths of rivers with major runs of salmon or other species would help to reduce contact between wild and caged fish and, consequently, the spread of disease from either.

Norway has adopted a much more thoughtful approach to the siting of operations as well as to the size of operations allowed in any one site since the early days of the industry when it developed with less planning and fewer controls.

Even so, at this time the majority of streams and rivers in Norway no longer have salmon runs. While aquaculture was not the only or even the primary cause of the demise of these runs, it did have an effect on at least some of them.

Measures to reduce escapes
One way to address the issue of escapes is through a code of conduct. A code could address such issues as improved cage engineering, better operating regimes, education of workers on their roles regarding this issue, improved monitoring, enforced prompt reporting, contingency planning, and more effective recovery programs.

The importance of proper siting
Specific targets could be set and monitored. Whoriskey (2000) has suggested an overall escape reduction target of 10% per year for 5 years. Once the goal is set, let the industry find the best ways to meet it. Proper siting could reduce the chance that escapes would happen at all, much less enter rivers with salmon runs.

Another way to reduce the impact of escapes from salmon aquaculture is to stock only sterile fish. Sterile fish programs are not foolproof; there is no way to guarantee that the organisms are always sterile.

However, as long as escapes persist, and perhaps even after they cease, sterile fish should be stocked to help to insure that escapes do not cause genetic pollution of wild salmon runs. Such programs will at least reduce the overall risk of interbreeding from escapes.

Credit

Extracts from "World Agriculture & Environment" by Jason Clay - buy the book online from Island Press

Subscribe to our mailing list

* indicates required
Donate to WWF

Your support will help us build a future where humans live in harmony with nature.