UNIT 23 

 MARINE MAMMALS OF THE PACIFIC REGION INCLUDING HAWAII 



animal samples in the Hawaiian and coastal Mexi- 

 can breeciing areas showed fewer genetic differ- 

 ences than did the two feeding areas. These differ- 

 ences are substantiated by the observed movement 

 of individually identified whales between Hawaii 

 and Mexico. There have been no individual 

 matches between 597 humpbacks photographed 

 in California and 617 humpbacks photographed 

 in Alaska. Few whales photographed in British Co- 

 lumbia have matched with a California photo- 

 graphic catalog, indicating that British Columbia 

 is an approximate geographic boundary between 

 feeding populations. 



Population Size 



Based on whaling statistics, the pre- 1905 

 population of humpback whales in the North Pa- 

 cific was estimated to be 15,000, but this popula- 

 tion was reduced by commercial whaling to ap- 

 proximately 1,200 by 1966. The present North 

 Pacific total almost certainly exceeds 3,000 hump- 

 back whales. 



Population estimates for the Calitornia/Or- 

 egon/Washington-Mexico stock range from 338 

 (CV = 0.29) to 626 (CV = 0.41). The most pre- 

 cise and least biased estimate is likely to be a 1 994 

 mark-recapture estimate of 597 (CV = 0.07) ani- 

 mals. The minimum population estimate lor 

 humpback whales in this stock from mark-recap- 

 ture methods is approximately 563 humpback 

 whales. 



Current Population Trend 



There is some indication that humpback 

 whales have increased in abundance in C^alilornia 

 coastal waters between 1979-80 and 1991, but 

 this trend is not significant. Mark-recapture popu- 

 lation estimates have increased steadily from 1 988- 

 90 to 1992-93 at about 5% per year. Although 

 the North Pacific population is expected to have 

 grown since it was given protected status in 1966, 

 the possible effects of continued unauthorized take, 

 incidental ship strikes, and gillnct mortality make 

 this uncertain. 



Status of Stock 



The PBR level is estimated as 1 . 1 whales; how- 

 ever, because this stock spends approximately half 

 its time in Mexican waters, the PBR allocation for 

 U.S. waters is one-half of the PBR estimate, or 

 0.5 whale/year. 



Humpback whales in the North Pacific were 

 estimated to have been reduced to 13% of carry- 

 ing capacity by commercial whaling, and the popu- 

 lation remains severely depleted. The population's 

 initial abundance has never been estimated sepa- 

 rately for the California/Oregon/Washington- 

 Mexico stock, but this stock was also probably de- 

 pleted by whaling. Humpback whales are formally 

 listed as endangered under the ESA, and conse- 

 quently the California/Oregon/Washington- 

 Mexico stock is automatically considered as a de- 

 pleted and strategic stock under the MMPA. Al- 

 though the estimated annual mortality due to en- 

 tanglement (1.2/yr) plus ship strikes (0.6/yr) in 

 California is greater than the estimated PBR level 

 allocation of 0.5 for this stock in U.S. waters, the 

 California/Oregon/Washington-Mexico stock ap- 

 pears to be increasing in abundance. 



EASTERN TROPICAL PACIFIC DOLPHINS 



Approximately nine species of dolphins are in- 

 cidentallv taken in the international purse-seine 

 fishery for yellowfin tuna in the eastern tropical 

 Pacific (ETP) waters off Mexico and Central 

 America. Only four species (representing 10 

 stocks) have experienced significant mortality as- 

 sociated with the tuna fishery. Since these four spe- 

 cies also occur in U.S. waters and are impacted by 

 U.S. fishing boats in the fleet, the NMFS South- 

 west Fisheries Science Center has routinely assessed 

 these dolphin populations. 



The greatest dolphin mortality occurred in the 

 1 960's and 1970's and led to dramatic declines in 

 abundance of the northeastern spotted dolphin 

 and eastern spinner dolphin stocks to one-fourth 

 of their pre-exploitation level in 19S9. Addition- 

 ally, trend data collected since 1975 indicate both 

 stocks are still significantly below the levels of 

 1975. In 1993, the NMFS listed both the north- 

 eastern offshore spotted and the eastern spinner 

 stocks as depleted under the MMPA because they 



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