Mike Kelly, U.S. Fish and Wildlife Service
At just about every public presentation I've given recently, this question comes up: Why aren't we doing anything to stop seals from eating salmon? I never have a good answer, so I've decided to do some digging and find out what the story is. Besides, what better way to find out if anyone reads my little articles than to maybe generate a few phone calls with a controversial topic?
Luckily, I didn't have to dig too far. The National Marine Fisheries Service document cited below summarizes pretty much everything that the federal government, local agencies, and other entities know about the topic. The report describes feeding habits, behavior, known impacts, ecological considerations, information gaps, and describes some specific attempts to control predation by seals and sea lions. Most of what I say comes either from this report, or from recent newspaper accounts. You can view the report on-line at: http://www.nwfsc.noaa.gov/pubs/tm/tm28/tm28.htm#toc
or click here http://www.nwfsc.noaa.gov/pubs/tm/tm28/tm28.htm#toc
Obviously, the federal government is considering the issue. Officials are looking at the issue, especially with recent Endangered Species Act listings for salmon, and increasing populations of seals and sea lions. The report states: In the 1994 Amendments to the Marine Mammal Protection Act, Congress directed that a scientific investigation be conducted to "determine whether California sea lions and Pacific harbor seals a) are having a significant negative impact on the recovery of Salmonid fishery stocks which have been listed as endangered species or threatened species under the Endangered Species Act . . . , or which the Secretary finds are approaching such endangered species or threatened species status; or b) are having broader impacts on the coastal ecosystems of Washington, Oregon, and California." It is the results of this investigation that make up the report.
The amendments to the Marine Mammal Protection Act also made it possible, under very strict conditions, for states to "lethally remove" problem seals and sea lions. These conditions were met at the Ballard Locks in Seattle, however no sea lions have yet been killed. After several different attempts to frighten and intimidate the sea lions, and after careful studies to document the problem, the state captured three of the five most notorious sea lions in 1996 and shipped them off to a park in Florida (the other two have not returned). With the prime suspects gone, the strategy now is to emit sounds that irritate sea lions to keep newcomers out of the locks. (Once they learn to catch salmon at the locks, they tend to ignore the sounds.) Since then, observations of predation by sea lions at Ballard have declined dramatically, and numbers of steelhead observed going up the fish ladder have actually increased. Of course, we have only two seasons of observations to go by, but it appears that the strategy is working.
The thing that biologists are careful to point out about the Ballard situation is that it was not a general problem with sea lions; it appears to have been a problem with a few individual sea lions. Many other sea lions are observed in adjacent waters of Puget Sound, however they do not appear to be feeding on steelhead. I personally think that this is a very important point. Let me explain why.
The report stresses that we need to consider the fact that we are managing ECOSYSTEMS.
Fading fast (hopefully) are the days when we simply managed one species, or other natural element, and expected everything else to remain the way we want it.
We have been burned too many times by not considering the broader implications of our management actions. (Just look at the problems we caused by removing logs from streams, thinking that it would help salmon by making it easier for them to swim up stream.) We have learned that ecosystems are very complicated things to manage indeed. Here is an excerpt from the report that gives examples of what ecosystem considerations we may face with managing seals and sea lions.
..reduction of pinniped (seals and sea lions, etc.) numbers may increase the population of other predators of commercial fish, thus reducing the population of the commercial fish because predatory fish are greater consumers of fish than marine mammals or sea birds. For example, South African Cape fur seals feed on both anchovy and squid, and if the fur seal population were reduced, the squid population which also consumes anchovies would increase and cause a reduction in anchovies available to the fishery. In another example, because Pacific harbor seals and California sea lions are predators of lamprey, decreasing the seal and sea lion population could increase the lamprey population. Lampreys are parasites which can affect both growth and survival of salmonids; consequently, pinnipeds may benefit certain salmonid populations by limiting the lamprey population.
So, it may be painful to sit and watch a seal kill salmon all day, but what if that seal also eats hundreds of lamprey, and other predatory fish? He may be more valuable to the salmon population alive than dead. Nature is messy and complicated. We are seeing more and more that the adage "everything is connected" looks to be true. Surprising relationships are being discovered in nature all the time - things that we would never have predicted. Anyway, had there been widespread "lethal removal" of sea lions at Ballard , other problems may have resulted.
So, the federal government has decided that it may be necessary to permanently remove seals or sea lions in certain cases, but we need to answer several questions first. Is the level of predation enough to jeopardize the run of fish? Is there some man-made constriction (like the locks at Ballard, or a hatchery intake, etc.), or other situation that makes the salmon easy prey? And if so, can the man-made problem be corrected? Which animals are really doing the most damage? Is there some other way to keep them away from the area? So far Ballard is the only place where all these questions have been answered. (By the way, the answers were: yes, yes, no, those five, and no.)
Whether you hate those salmon-eating-stink-breaths, or are a big time pimped hugger, or fall somewhere in between, you've got to hand it to them - they are SMART. They learn to ignore and outwit our best attempts to fool and frighten them. When they've been captured and moved (as far as from Ballard to California), they have come right back and have been impossible to catch again. And in at least one case when researchers threw firecrackers, or "seal bombs," the sea lions began to surface in an unpredictable pattern - like a fighter pilot using evasive maneuvers.
Anyway, there are clear reasons why we don't just shoot the seals and sea lions to save the salmon. However, we humans create all sorts of difficult situations, and are forced to make difficult decisions as a result. You won't find me advocating the "lethal removal" of seals or sea lions anytime soon, but I am certainly willing to help examine a particular situation. So, call me if you know of a place, or places, in the Chehalis River Basin where seals or sea lions are preying on salmon that are concentrated due to a man-made structure. I can at least help you document the situation, and perhaps some alteration can be made to the structure, or some other non-lethal measure can be taken.
Mike Kelly, U.S. Fish and Wildlife Service, Chehalis Fisheries Restoration Program, 360-753-9560.
Reference National Marine Fisheries Service (NMFS). 1997. Investigation of Scientific Information on the Impacts of California Sea Lions and Pacific Harbor Seals on Salmonids and on the Coastal Ecosystems of Washington, Oregon, and California. U.S. Department of Commerce, NOAA Tech. Memo. NMFS-NWFSC-28, 172 p.
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