Risk assessments urged for fish escaping from net-pen aquaculture

Substantial risks to native fish stocks argue for evaluation of dangers

The substantial risk to salmon stocks posed by salmon that escape from net-pen farms argues for risk assessments of all types of marine fish farming, according to an article published in BioScience. Rosamond Naylor of Stanford University and nine coauthors conclude in their article that without a firm policy mandate for risk assessment of escaping farm fish, aquaculture will “almost certainly lead to extensive competition between wild fish and continuously released farm fish–or widespread establishment of exotic fish species–and thus to a further decline in wild fish stocks.”

Naylor and her coauthors conclude that, despite some efforts by aquaculture companies to curtail farm salmon escapes—such as using stronger net materials—the efforts are inadequate, as monitoring and enforcement of regulations governing escapes are weak. An estimated two million farm Atlantic salmon escape each year into the North Atlantic, and millions more have escaped on the western coasts of North American and South America. Farm Atlantic salmon are more aggressive and faster-growing than native fish, with which they compete for food.

Interbreeding with native salmon stocks leads to long-term loss of fitness and productivity in wild populations and threatens their genetic diversity. Moreover, farmed salmon appear to have transmitted parasites and infections to wild stocks. Escaped farm salmon are now successfully breeding in the wild in Norway, Ireland, the United Kingdom, and North America. Incipient feral Atlantic salmon populations have been found in rivers in British Columbia and South America.

Naylor and her coauthors point out that understanding the risks associated with escapes from salmon farms is especially important because net-pen aquaculture of many fish species is expanding. Other marine finfish now being farmed include Atlantic cod, sablefish, halibut, Pacific threadfin, mutton snapper, bluefin tuna, turbot, sea bass, and sea bream.

The study is described in detail in the May 2005 issue of BioScience, the monthly journal of the American Institute of Biological Sciences. Journalists may obtain copies of the article by contacting Donna Royston, AIBS communications representative. BioScience publishes commentary and peer-reviewed articles covering a wide range of biological fields. The journal has been published since 1964. AIBS is an umbrella organization for professional scientific societies and organizations that are involved with biology. It represents 89 member societies and organizations with a combined membership of about 240,000.