MARINE MAMMAL COMMISSION - Annual Report for 1995 



Russia on counts of walrus at haul-out sites, walrus 

 distribution, population censuses, harvests, and other 

 topics. The work is scheduled to be completed early 

 in 1998 and is being done in conjunction with a 

 project to develop a geographic information system 

 database of biological and ecological data for the 

 entire Bering Sea ecosystem. The telemetry studies 

 involved attaching VHF and satellite tags to 17 

 walruses in Bristol Bay to determine haul-out patterns 

 and to locate feeding areas. The results are expected 

 to be available in 1996 when work is planned to field- 

 test new global positioning system satellite tags that 

 provide more accurate location data. If successful, it 

 is hoped that the new tags can be used on walruses 

 hauled out along the ice edge to assess behavioral 

 responses to vessel traffic and aircraft overflights. 



Monitoring studies carried out by the Fish and 

 Wildlife Service's Marine Mammals Management 

 Office have focused on three areas, in addition to the 

 harvest monitoring work noted above. In 1995 the 

 Office contracted for laboratory analyses of contam- 

 inant levels and effects in walrus livers and kidneys 

 collected in cooperation with Native hunters during 

 spring hunts at Gambell and Savoonga between 1992 

 and 1994. Past studies have found high levels of 

 mercury and cadmium in these tissues, and the studies 

 are part of a continuing effort to detect trends and 

 assess possible effects. A report of the work will be 

 available early in 1996. 



Also in 1995 the Division supported laboratory 

 analyses of blood samples from 20 walruses for signs 

 of unusual diseases. None were found. It was also 

 determined that there were no signs of exposure to 

 several highly contagious animal diseases, such as 

 morbillivirus or brucellosis. To monitor walrus 

 health, the Service also has encouraged Native hunters 

 to report observations and collect samples from 

 walruses with unusual physical conditions. Among 

 other things, laboratory analyses of samples collected 

 by Native hunters found two samples that were 

 apparently coated with crude oil and two liver samples 

 with fibrosis possibly caused by infection. 



Pacific Walrus Stock Assessment 



In 1994 amendments to the Marine Mammal 

 Protection Act directed the Fish and Wildlife Service 



to prepare stock assessments for marine mammal 

 stocks under its jurisdiction. The purpose of the 

 assessments is to provide a basis for managing the 

 incidental take of marine mammals in commercial 

 fishing gear. Among other things, the assessments are 

 to include estimates of population size and maximum 

 productivity, and to calculate the potential biological 

 removal level (not including natural mortality) that 

 could be taken annually and still allow the stock to 

 reach or remain within optimum sustainable popula- 

 tion levels. The assessments also are to provide 

 information on annual incidental-take rates and to 

 determine whether the stock is a "strategic" stock, 

 which could require special management action (see 

 Chapter IV). 



The Service circulated draft stock assessments for 

 walruses and certain other species in August 1994. 

 As described in the previous annual report, the 

 Commission provided comments to the Service on 1 

 December 1994. The draft assessment concluded, 

 among other things, that the Pacific walrus stock 

 should be considered a strategic stock because the 

 combined average annual harvest in the United States 

 and Russia over the past 30 years exceeded its esti- 

 mated potential biological removal level. In its 

 comments to the Service on this conclusion, the 

 Commission noted that if the analysis was limited to 

 harvest levels since 1990 — the date of the population 

 estimate used to calculate the potential biological 

 removal level — the average annual harvest number 

 would not exceed the potential biological removal 

 level. The Commission, therefore, recommended that 

 the Service reassess its finding that the stock should 

 be considered strategic. 



Final stock assessments were provided to the 

 Commission by the Service in October 1995. The 

 assessment for Pacific walruses concluded that the 

 stock probably numbers between 200,000 and 250,000 

 animals, but that, based on coefficients of variation 

 from the most recent population survey, the best 

 minimum stock estimate is 188,316 animals. It also 

 concluded that the best current estimate of the maxi- 

 mum productivity rate is eight percent per year. 



Using these and other data, the Service calculated a 

 potential biological removal rate of 7,533 animals per 

 year. National Marine Fisheries Service observer data 



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