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Commercial Fishing vs. Salmon Farming
07/14/03
Commercial salmon fishing and commercial salmon farming are not always evaluated with exactly the same criteria. One often quoted supposed example of salmon farming's alleged non-sustainability is the amount of natural forage incorporated into salmon diets. It is said to take up to four kg of natural forage to produce a kilogram of farmed salmon.
Therefore for the year 2000, when total Canadian (BC and NB) farmed salmon production was 70,000 mt (Price Waterhouse Coopers 2001), it would have taken 280,000 mt of natural forage incorporated into the salmon feed to achieve this figure.
How much natural forage does it take to support the hatchery portion of the west coast commercial salmon harvest? More, it turns out. Let's look at just Alaska salmon hatchery programs. As is well known, natural salmon populations in Alaska are very well managed, so Alaska hatchery programs exist only to provide additional salmon for harvest by the commercial industry, and are not used there to rebuild depressed populations.
In the year 2000, Alaska hatcheries produced 567,000 mt of salmon that were either captured in the commercial fishery or returned to the hatchery (Waknitz et al. 2003). Had these fish never been released, the natural forage they subsequently consumed would have been available for wild salmon and other species. So the natural organisms eaten by Alaska hatchery salmon constitute a man-made ecological cost just as surely as the salmon feed eaten by farmed fish. Many marine ecologists report that it takes about 10 kg of natural prey to produce one kg of natural predator. Let's say it takes only 5 kg. Therefore, it took at least 2,835,000 mt of natural prey to support the hatchery component of the Alaska salmon fishery in 2000. At the accepted 10:1 ratio, Alaska hatchery programs would require 5,670,000 mt of natural prey items.
Add the fish released from BC and lower 48 hatcheries and the total ecological cost would increase by about 25%. Obviously, salmon farms are more efficient in reducing the ecological cost to natural forage populations than using hatcheries to provide salmon for commercial harvest.
There are numerous additional ecological costs of commercial salmon fisheries that are seldom mentioned when listing supposed or real ecological costs of salmon farming. A short list of such costs would include:
Cost to fresh water habitat. Total harvest of Pacific salmon in west coast commercial fisheries numbers in the scores of millions of salmon annually. It has recently become known that salmon carcasses are vitally important to the nutrient input in Pacific Northwest coastal forests. As a result of west coast commercial salmon fishing activities, local forest ecosystems are deprived of many millions of mt of nutrients that were removed from marine ecosystems by commercial harvesters.
Hooking mortality/net dropout. The exact impact of hooking mortality and dropout from nets is not known, but attempts to estimate this impact should be included in discussions of the ecological footprint of commercial salmon harvest. A review of the literature suggests that hooking mortality in the commercial troll fishery could be between 10% and 20% of the total troll harvest.
Ghost nets. This cost is largely unknown, but is thought to be quite serious by the environmental and fishing communities.
Pollution from salmon processing plants. Without question, the organic enrichment of the natural benthic environment by salmon/fish processing plants is vastly greater than the organic enrichment beneath salmon farms. For example, the accumulation of organic waste at some fish plants in Alaska is up to 7 meters deep, compared to organic accumulation of just a few centimeters at BC salmon farms (Waknitz et al. 2003).
Interestingly, EPA has recently fined fish processing plants in Alaska for NPDES violations while Washington salmon farms, operating under the same NPDES program, haven't been sanctioned.
Adverse marine mammal interactions. Without question, this is a significant problem in both commercial salmon fisheries and at salmon farms. Yet marine mammal impacts by commercial salmon fishers seldom is evaluated in discussions of ecological comparisons between salmon farming and commercial salmon harvest (see Wynne 1990).
Having said this, one might conclude that I feel that the risks associated with commercial salmon fishing are unacceptable. On the contrary, I think that overall, salmon fishing risks are small, but unavoidable. After all, salmon fishing is a human endeavor; therefore the risks can't ever be zero. However, since a thorough review of the literature suggests that the risks of salmon farming are generally less than those associated with salmon fishing, then salmon farming automatically becomes acceptable as well.
F. William Waknitz Research Fisheries Biologist National Marine Fisheries Service P. O. Box 130 Manchester, WA 98353
1-360-871-8322
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