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National Marine Mammal Laboratory

(Quarterly Report for Jan-Feb-March 1999)

Gray Whale Workshop

The National Marine Fisheries Service (NMFS) sponsored a review of the status of the eastern North Pacific stock of gray whales (Eschrichtius robustus).  The workshop was held by the National Marine Mammal Laboratory (NMML) in Seattle on 16-17 March 1999.  Thirty-seven people attended. The review concluded the 5-year assessment of the stock following the June 1994 delisting from the List of Endangered and Threatened Wildlife.  Based on the continued growth of this population (rising at 2.5% per year; currently at an estimated 26,600 individuals) and the lack of evidence of any imminent threats to the stock, the participants recommended to continue this stock’s classification as nonthreatened.  Other reports presented at the workshop showed that the widely reported delay in the southbound migration and unusually high levels of strandings in Mexico this year were not significantly different from other years. Those attending the workshop concluded that abundance monitoring should continue and that, ideally, research should continue on human impacts to critical habitats.  This stock’s annual migrations along the highly populated coastline of the western United States and its concentration in limited winter and summer areas may make it particularly vulnerable to impacts from commercial or industrial development or local catastrophic events.

By Dave Rugh and Marcia Muto.

Pinniped Predation on Endangered Salmonids

NMML staff are completing laboratory analysis of harbor seal and sea lion food habits in the Columbia, Umpqua, and Ozette Rivers in preparation for the workshop  “Assessing Impacts of Pinniped Predation on Endangered Salmonids” scheduled for 21 - 23 April in Newport, Oregon. The objectives of the workshop are 1) to evaluate methods of estimating consumption of ESA (Endangered Species Act)-listed salmon and 2) to evaluate salmon life history models for evaluating the impact of measured predation on the recovery of listed fish runs.    At the workshop NMML staff  will present the reports “Food habits of harbor seals in the lower Columbia River” and “Prey consumption estimates for harbor seals in the lower Columbia River” and the draft reports  “Food habits of harbor seals from Umpqua River” and “Food habits of harbor seals, California sea lions and Steller sea lions at Ozette River.”

An interesting aspect of the studies of harbor seals at the Umpqua River has been the potential harbor seal predation on the endangered Umpqua River cutthroat trout.  Scat collections from autumn of 1997 were cleaned and the prey remains were identified.  Samples contained a few salmonid otoliths and identifiable bone.  There was no indication of feeding on cutthroat trout, although a number of the samples contained bone of salmonids which could not be identified to species.  In a collaborative effort, the Northwest Fisheries Science Center (NWFSC) extracted DNA from those bone samples and has been able to provide species identifications in almost all of the samples.  The extraction of DNA from prey remains is an important new tool which aids in distinguishing between species and perhaps even stocks of salmonids in studies along the West Coast.

By Bob DeLong.

Steller Sea Lion Prey and Foraging Studies

Scientists from NMFS and the U.S. Fish and Wildlife Service (USFWS) conducted an echo  integration-midwater trawl survey for Steller sea lion (Eumetopias jubatus) prey at three sites in Alaska waters during 2-25 March 1999 aboard the USFWS vessel Tiglax for a total of 23 sea days.  The area of operations included the Kiska, Kasatochi, and Ugamak rookeries and waters surrounding these sites.

A total of 401 km of transects were run at the three sites, 276 km during the day and 125 km at night.  At Kiska, Kasatochi, and Ugamak 40%, 100%, and 90% of the transects were completed, respectively. Long-line sets or midwater trawls were not conducted due to rough weather. One neuston surface tow was made to verify echosign, verifying the presence of larval fish. Preliminary estimates suggest that midwater biomass was greatest at Ugamak rookery and declined to the west, but these data remain to be analyzed. Additionally, oceanographic seabird and marine mammal sighting data were recorded throughout the trip, all of which are currently being analyzed.

The cruise was moderately successful, though rough weather conditions were more prevalent than in past trips.  The vessel and crew performed admirably during periods of  stormy weather. The vessel continues to provide an excellent platform for winter work.

By Kathryn Chumbley.