103 



Eastern Tropical 

 Pacific (ETP) Dolphins 



At least four species (13 stocks) of dol- 

 phins are incidentally taken in the interna- 

 tional fishery for yellowfin tuna in the 

 tropical Pacific waters off Mexico and Cen- 

 tral America (about 57,000 were killed in 

 1990). Because those four species also 

 occur in U.S. waters, and because the 

 United States is the major market for the 

 fishery, the NMFS has assessed the dol- 

 phin populations. 



The northern stock of spotted dolphins 

 is estimated at 658,300-2,205,500 and the 

 southern stock at 85,800-451,900 (1986- 

 89). Dolphin sightings suggest that both 



stocks have declined. Eastern spinner dol- 

 phins number 391,200-754,200, while 

 whitebelly spinner dolphin stocks number 

 about 363,300-1 ,398,400. The data are too 

 variable to determine population trends. 

 Common dolphin abundance for the north- 

 ern, central, and southern stocks were 

 about 177,700, 568,000, and 1,657,500, 

 respectively. Differences in yearly esti- 

 mates suggest that 1 ) variances are under- 

 estimated, 2) immigration is extensive, or 

 3) annual calf production or mortality may 

 vary greatly. Estimates of striped dolphin 

 abundance is 652,000-2,251,300. 



Harbor Porpoise 



Harbor porpoises range throughout North 

 American coastal waters. Surveys of them 

 have been conducted off California since 

 1984, periodically off Oregon and Wash- 

 ington, and not at all off Alaska. Harbor 

 porpoises tend to concentrate at the mouth 

 of the Columbia River and at many other 



bays. Estimates of abundance are 1 1,100 

 in California (3,274 in central California 

 alone which is 30-97% of the carrying ca- 

 pacity). About 700-1,000 range Wash- 

 ington's north coast. The species was once 

 abundant in Washington's inland waters 

 but is rare there now. 



Bowhead Whale 



The endangered bowhead whale has 

 ranged as far as the polar ice fields of the 

 Northern Hemisphere. Total prewhaling 

 abundance exceeded 120,000, but by 

 1900 it was probably in the low thousands. 

 In the (J.S. western Arctic, 18,650 bow- 

 heads were killed by Yankee whalers be- 

 tween 1848 and 1914 from a population 



estimated at less than 20,000. The take by 

 Alaska Eskimos has averaged 20-40 

 whales per year since 1914. The present 

 population, 7,500, is about 40-60% of its 

 1848 carrying capacity. The stock has 

 been increasing since commercial whaling 

 ended and has increased 3.1%/year since 

 1978 (Fig. 23-1). 



Gray Whale 



Still listed under ESA as endangered are 

 the two stocks of North Pacific gray whales. 

 The eastern North Pacific or "California" 

 stock was heavily exploited by Yankee 

 whalers in the last half of the 1 9th century. 

 The present stock size, 21,1 13, is equal to 



or larger than the size of the 1846 popula- 

 tion of 15,000-20,000. Population growth 

 rate is 3.2%/year despite a Soviet subsis- 

 tence catch of 167 whales per year (Fig. 

 23-2). 



Humpback whale 



The endangered humpbacks in the eastern 

 North Pacific Ocean migrate between the 

 subtropical waters of Hawaii and coastal 

 Mexico during the calving season and the 

 temperate and subarctic waters of north- 

 ern California and Alaska where they feed. 



The population is estimated at 1,300- 

 2,000. Prewhaling numbers (ca. 1850) 

 were about 15,000, but this may have in- 

 cluded humpbacks from the western North 

 Pacific Ocean. No information exists on 

 population trends. 



