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September 21, 2007

It's a Fish-Eat-Fish World

Fishery management is a complex and often difficult process, no doubt about it. Anyone who has spent much time "in the loop," particularly at the state and federal levels, knows that what may appear to be a simple solution to a resource problem can, in fact, open up a 55-gallon drum of worms. Big worms. One thing always seems to lead to another, mainly because most creatures that live in the ocean are somehow interrelated, either through habitat or predator-prey relationships. Fiddling around with nature can trigger far-reaching consequences.

Fishery scientists and managers have, for some time now, recognized this interaction, particularly as it applies to predators and prey. One prime example is that newly resurgent stocks of striped bass are finding too little to eat because harvest levels of menhaden-an important forage species for stripers-are too high. Another is increasing commercial catches of squid, considered an "underutilized" species that technically may not currently be overfished-but are we factoring in its importance to the recovery of large pelagics such as bluefin tuna, swordfish, marlin and sharks?

Things can get even more complicated. Predator-prey interactions may be felt across a number of food-chain levels, resulting in what's known as a "trophic cascade." For instance, populations of sea otters in the waters of Alaska have declined in several areas, with the result that their principal prey, sea urchins, have increased dramatically. All these sea urchins have caused a ten-fold decline in kelp, which acts as a breakwater against wave action, and this has resulted in increased erosion of the shoreline. And why the decline in sea otters? It appears that it's due to increased predation by killer whales, which may be finding fewer of their regular prey-sea lions and harbor seals-which are perhaps declining due to a reduction in forage fish such as pollock, a result of heavy commercial fishing pressure. Gets involved, doesn't it?

"Ecosystem-based" management, in which a number of interdependent species are taken into consideration in a fishery plan, has been receiving increased attention recently. One champion of the cause, the National Coalition for Marine Conservation (NCMC), has been working with several management bodies to encourage them to begin developing plans that incorporate this principle and to move away from the traditional single-species focus. The NCMC has also drafted changes to the Magnuson-Stevens Act that would require ecosystem-based management, and has published a report that serves as a template for the process entitled "Conservation in a Fish-Eat-Fish World: Managing Related Predator and Prey Species in Marine Fisheries" that's being distributed to state and federal fishery management agencies, NGOs and Congress. "An ecosystem approach to management is a natural outflow of our increasing knowledge of the ocean and our expanding circle of concern for all marine species," says NCMC president Ken Hinman.

We fully support this approach. Sure, there will be resistance and plenty of challenges along the way, but as we learn more about how critically dependent our marine resources are upon each other, it's the only way to go.

¿ ¿ ¿ ¿-- July, 2001