Decline of the Steller Sea Lion in Alaskan Waters Untangling Food Webs and Fishing Nets (2003) / Chapter Skim
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7. Information Needs and Recommendations
7. Information Needs and Recommendations
Pages 152-160
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From page 152... ...
Second, the western stock has not shown signs of recovery despite substantial restrictions imposed on commercial groundfish fisheries since 1999. This has raised questions about the presumed interaction between sea lions and commercial fishing activity.
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From page 153... ...
It remains unclear whether existing fisheries restrictions and closed areas should be treated as "precautionary" policies with respect to Steller sea lions. Some of the most credible hypotheses about the recent declineincluding killer whale predation, continued illegal shooting and subsistence harvest, productivity declines due to regime shifts, and persistent changes in fish community structure due to predator-prey interactionsare not addressed by reducing the biomass of fish caught in sea lion critical habitat.
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From page 154... ...
Greater attention must be devoted to a socioeconomic study of all fishers and subsistence hunters, including efforts to enlist their knowledge of historic and contemporary Steller sea lion population trends. The possibility that killer whale predation is a major factor in the decline of the Steller sea lion population is not easily dismissed.
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From page 155... ...
Transient animals are known to feed primarily on marine mammals such as sea lions, in contrast to resident killer whale pods that are believed to feed primarily on fish. Efforts should be made to determine if killer whales follow fishing vessels or are disproportionately aggregated around Steller sea lion breeding or haulout sites.
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From page 156... ...
Second, fishery observer records should be consulted for accounts of killer whale attacks on sea lions. These records may constitute a valuable resource on plausible top-down influences on the sea lion population.
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From page 157... ...
as the experimental units. Also, sea lions are thought to be more vulnerable near rookeries because of the presence of pups and juveniles and because females must forage near the rookeries so they can return to nurse their pups.
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From page 158... ...
Under this option, the most critical monitoring needs would be detailed local Steller sea lion censuses and spatial analysis of fish population changes for each experimental unit in the overall design.
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From page 159... ...
Some of the many considerations for the design of such an experiment include Fished area (under normal management plans) The groundfish fisheries have been the focus of restrictions to protect sea lions based in part on the large amount of biomass removed by this fishery, but the potential effects of other fisheries have not been as thoroughly examined.
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From page 160... ...
. There should be a contingency plan to modify or curtail fishing in open areas if these areas show dramatic sea lion mortality as might occur under some scenarios, for example substantial fishery bycatch of Steller sea lions.
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