198 



W. B. KING, R. G. B. BROWN, AND G. A. SANGER 



set), whereas the mothership fishery usually 

 operates between mid-May and late July. As- 

 suming similar seabird densities and catch per 

 unit of effort in the areas of the land-based 

 and coastal fisheries, the estimated annual 

 mortality is between 214,500 and 715,000 

 birds. Since 1952, as many as 4.7 million birds 

 may have been killed by the Japanese salmon 

 gill-net fishery. It must be stressed that sea- 

 bird densities and catch per unit of effort are 

 not known to be similar for the areas in ques- 

 tion; consequently the projection of bird kill 

 figures from one area to all three is 

 speculative. 



In the mothership area and adjacent seas to 

 the east, in addition to murres (48% of birds 

 killed), significant numbers of shearwaters, 

 Puffinus spp. (27%); puffins (9%); and ful- 

 mars, Fulmarus glacialis (5%) are killed, as 

 are lesser numbers of small alcids, albatrosses 

 (Diomedea spp.), and storm-petrels. The 

 murres and puffins taken in the mothership 

 area are of U.S. and U.S.S.R. origin, and the 

 shearwaters come from New Zealand, Aus- 

 tralia, and Chile. In the coastal fishery area, 

 Japanese and U.S.S.R. alcids are taken. 

 Available knowledge of the populations of the 

 species making up the bulk of the kill, which 

 has been taking place for 20 years, is insuffi- 

 cient to suggest whether their annual repro- 

 duction can tolerate such losses. Prohibition 

 of fishing within 160 km of North Pacific sea- 

 bird breeding islands would help to decrease 

 losses of alcids of U.S. origin, but would not 

 help the shearwaters from the southern 

 hemisphere. 



Comparison of statistics of the salmon 

 fisheries and associated bird kills from the 

 North Atlantic and the North Pacific shows 

 that the North Atlantic salmon fishery is con- 

 centrated in a relatively small area which is 

 also along a major migration pathway of 

 murres. Virtually all seabird mortality is con- 

 fined to one species. Enough information is at 

 hand to indicate that this cause of mortality, 

 in conjunction with others known to be sig- 

 nificant, is causing a drastic decline in the 

 thick-billed murre population. 



In the North Pacific, on the other hand, the 

 fishery is more widely dispersed and the ratio 

 of seabirds to salmon caught is much lower. 

 Furthermore, several species are subject to 

 mortality. No information is available to indi- 



cate whether alcid populations (which make 

 up two-thirds of the kill) are stable or decreas- 

 ing. The shearwaters, primarily sooty (Puffi- 

 nus griseus) and slender-billed (P. tenuiros- 

 tris), appear to be able to sustain not only 

 these losses but also a sizable harvest of birds 

 of the year (the so-called muttonbirds) on 

 their New Zealand and Australian breeding 

 grounds. Thus, although the latest estimates 

 of the total standing stock of seabirds in the 

 North Pacific in summer may be as high as 

 100 million (Sanger and King, this volume), 

 and thus only about 1 of every 200 birds in the 

 North Pacific region may be caught, the fact 

 that a few species, particularly murres, are se- 

 lectively caught raises questions about the 

 impact of this fishery on populations of these 

 species. 



The U.S. -Japan Migratory Bird Convention 

 of 1973 specifically protects all of the species 

 thought to be subject to gill-net mortality in 

 the Pacific. Thus, the Japanese salmon fleet 

 apparently operates in constant violation of 

 this convention. 



Mortality of Albatrosses 



A recent analysis of recoveries of Laysan 

 albatrosses (Diomedea immutabilis) and 

 black-footed albatrosses (D. nigripes) banded 

 on the northwest Hawaiian chain from 1937 

 to 1969 showed that of a sample of 532 re- 

 covered birds, 57.4% of the Laysan species 

 and 49.5% of the black-footed species were 

 caught on fishhooks or in nets, and the means 

 of recovery of many additional birds was 

 thought to have been the same (Robbins and 

 Rice 1974). It is likely that the large majority 

 are taken on Japanese and U.S.S.R. longline 

 tuna fishing gear. Although this cause of mor- 

 tality is insignificant in terms of the total 

 population of either species (only 0.2% of 

 banded Laysan and 0.8% of banded black- 

 footed albatrosses have been recovered by 

 any means away from their breeding 

 grounds), these species are protected by the 

 U.S.-Japan Migratory Bird Convention. 

 Furthermore, the possibility exists that indi- 

 viduals of the endangered short-tailed alba- 

 tross (Diomedea albatrus) might be killed in 

 this manner. 



