It's not just fishing

(from the April, 2006 issue of National Fisherman)

I just dug into the spiny dogfish situation in the Northeast (see The Dogfish Follies at http://www.fishnet-usa.com/dogfishfollies.html), and was intrigued by the fact that it apparently took 2.4 million metric tons of prey - including hake, cod, pollock, ling, haddock, porgies, croakers and flatfish - to support last year's standing crop of 400,000 tons of horn dogs. This got me interested in the impacts of predation by other protected species.

Finding population estimates of these species is fairly easy (the various Stock Assessment Reports are available via the Protected Resources section of the NMFS website), but determining how much of what they eat isn’t. Fortunately, I stumbled across  an article, Food Webs in the Ocean: Who Eats Whom and How Much? (by Andrew Trites of the Marine Mammal Research Unit at the Fisheries Centre of the University of British Columbia) that shed quite a bit of light on the subject. Dr. Trites wrote “consumption of marine organisms, expressed as a percentage of an individual’s body weight per day, ranges from about 4–15% for zooplankton, to 1–4% for cephalopods, 1–2% for fish, 3–5% for marine mammals and 15–20% for sea birds.”

So I took a look at the possible impacts of some other protected species on our East coast fisheries. Starting out with Flipper and his friends, I found that in our neck of the western North Atlantic there were 30,000 bottlenose dolphin, 31,000 common dolphin, 61,000 striped dolphin, 36,000 spotted dolphin and perhaps 30,000  white sided dolphin, (these are all 1998 figures, the most recent available, though “anecdotal” observations indicate that they have been increasing since then). So in 1998, we can conservatively estimate at least 180,000 of these efficient predators were eating fish off our shores, that many of them were species that fishermen – both recreational and commercial – are seeking, and that many others were species that economically important species eat. If we assume an average weight of 150 pounds per porpoise or dolphin (your guess might be better than mine), they are collectively consuming a million pounds of fish a day, or 180 thousand metric tons a year. The 14,000 pilot whales, if we assume an average weight of 3,000 pounds each, are eating another 300 thousand tons a year.

What about seals? The 100,000 harbor seals in Maine’s water, with an average weight of 200 pounds, would consume 130,000 metric tons of fish and invertebrates a year.

So we have a handful of “protected” species, all presumably increasing in numbers each year, that are conceivably consuming some 3 million metric tons of commercially and recreationally important species, or the species that those species eat, off our East coast. In 2004 the commercial landings of all species of finfish and shellfish from the Atlantic coastal states were 750 thousand metric tons.

The situation can’t be much different on the West coast or in Alaska’s waters.

But according to our current management philosophy, this doesn’t make much of a difference. Just take a look at the current situation in the New England groundfish fishery. After what seems like eons of cutbacks, the fleet is facing the latest; a proposed reduction to 22 days at sea (55% below last year’s allocated days). The first allocated groundfish DAS - that’s “Days At Sea” for those fortunate enough to be unaware of this acronym – were on the order of 200 per year ten or so years ago. They’ve been ratcheted steadily downwards ever since. Not too surprisingly, landings have followed suit. In 2004, the total landings of the major groundfish species -  cod, haddock and yellowtail flounder - were under 25,000 metric tons. Post-Magnuson highs were 50,000 metric tons for cod, 25,000 for haddock and 33,000 for yellowtail flounder. After two decades of increasingly restrictive management and corresponding declining harvests, the stocks still aren’t where “they should be. ” Accordingly, the managers insist that more, and more debilitating, cutbacks in fishing are deemed to be necessary. But in those same two decades all of these protected species have been increasing with no limits.

Nils E. Stolpe