Pacific Sleeper Shark Population Increasing

Aug 18 • Predation • 5 Views • Comments Off on Pacific Sleeper Shark Population Increasing

Information suggests that Pacific sleeper shark abundance is increasing. Pacific sleeper shark data was analyzed from fishery independent longline surveys in the Gulf of Alaska and the Bering Sea to determine the trend in abundance and whether any change was statistically significant. Relative population numbers of Pacific sleeper sharks captured in the NOAA Fisheries domestic sablefish longline surveys increased from a low of 79 in 1988 to a high of 1,779 in 2000.

The most substantial increase in relative population numbers occurred between 1992 and 1993, and relative population numbers remained high from 1994 to 2000. For Pacific sleeper shark relative population numbers in the longline surveys between the years 1989 and 2000, 95% bootstrap confidence intervals did not overlap for all years. This suggests that there has been a significant increase (at the 95% confidence level) in the relative abundance of Pacific sleeper sharks captured in the Gulf of Alaska and Bering Sea for some years during this period.

The increase in relative population numbers was driven largely by Pacific sleeper shark catches in Shelikof Trough, a deepwater Gulf of Alaska gully on the continental shelf between Kodiak Island and the Alaska Peninsula. Pacific sleeper sharks appeared to be relatively abundant in this area. Pacific sleeper sharks may be relatively abundant in other areas, such as on the continental shelf of the Gulf of Alaska and the Bering Sea at depths less than 200 m, but these areas are not routinely sampled by the sablefish longline survey.

In 2004 Yves Cherel, of the Centre d’Etudes Biologiques de Chize in Villiers-en-Bois, France, and Guy Duhamel of the Museum National d’Histoire Naturelle, Paris, collected 36 sleeper sharks taken by trawlers in waters off Antarctica. The sleeper shark stomachs contained the remains of at least 49 colossal squid and eight giant squid. Sleeper sharks are proving to be one of the great marine predators.

 

References
Castro, Jose’. 1983. The Sharks of North American Waters. Texas A&M University Press, Texas A&M University.

Eschmeyer, W.N. and E.S. Herald 1983. A field guide to Pacific coast fishes of North America: from the Gulf of Alaska to Baja California. Boston, Mass: Houghton-Mifflin Co.

Hart, J.L. 1973. Pacific Fishes of Canada. Bull. Fish. Res. Bd. Canada 180:44-47.

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