Carter and others 



Chapter 27 



Mortality in Gill Nets 



week during the summer. Fishermen have reported further 

 (DeGange, pers. comm.) that murrelets have been killed 

 occasionally near Raspberry Island at the northwest end of 

 Kupreanof Strait, involving mostly juveniles. In other areas 

 near Kodiak Island (e.g.. Cape Uganik and the south side of 

 Kupreanof Strait), none were known to be killed. A few 

 murrelets per year also were reported killed in nets on the 

 east side of Cook Inlet near Clam Gulch (between Kenai and 

 Homer). This mortality occurred during nine net sets over 

 the fishing season, whereas about 150 net sets occur in this 

 area throughout the year. Puffins (Fratercula sp.) and other 

 seabirds (possibly including murrelets) are taken occasionally 

 in nets set near Chisdik Island on the west side of Cook Inlet. 

 However, no seabirds were reported killed in nets while 

 fishing north of Chisdik Island. 



Since 1990, official observers were placed on fishing 

 boats in Prince William Sound and near the Copper River 

 delta by the National Marine Fisheries Service (Mendenhall 

 1992). Observers reported mortalities of 36 and 25 

 Brachyramphus murrelets (84 percent Marbled Murrelets) in 

 1990 and 1991 (Wynne and others 1991, 1992). Extrapolating 

 from observed fishing effort (3.9 percent and 3.5 percent nets 

 observed in 1990 and 1991, respectively), then, as many as 

 923 and 714 murrelets may have been killed in gill nets in 

 Prince William Sound in 1990 and 1991, respectively (Piatt 

 and Naslund, this volume; Wynne and others 1991, 1992). 

 Extrapolating 1990 data from mean catch per week data, 

 Wynne and others (1991) estimated that 1,468 seabirds (95 

 percent confidence limits: 836-2,100) were killed in Prince 

 William Sound in 1990, 97 percent of which were murrelets. 

 Using this level of observed mortality in Prince William 

 Sound. Piatt and Naslund (this volume) estimated annual 

 mortality of 900, 1 100, and 300 murrelets in Southeast Alaska, 

 lower Cook Inlet, and along the Alaska Peninsula, respectively. 

 Thus, the Alaska total may approach about 3,300 birds 

 annually. However, it is likely that gill-net mortality rates 

 differ in other areas, and it may be inappropriate to apply 

 mortality rates from Prince William Sound elsewhere. 



Offshore Mortality 



Only one bird was reported killed in offshore high-seas 

 drift-net fishery near the western Aleutian Islands through 

 1988 (DeGange 1978, DeGange and others 1985, Mendenhall 

 1992. Sealy and Carter 1984). However, murrelets do not 

 usually occur far offshore, and there does not appear to be a 

 significant problem in offshore fisheries. 



Outlook 



Additional observer programs are required to estimate 

 total mortality of Marbled Murrelets and other seabirds 

 throughout Alaska (see DeGange and others 1993). Effort 

 should focus on American nearshore fisheries. In 1992, a 

 United Nations resolution was passed which ended large- 

 scale pelagic driftnet fisheries, and this problem appears to 

 be resolved for the time being. On the other hand, declining 

 populations of Marbled Murrelets in Alaska cannot sustain 

 the apparent levels of mortality in fishing nets. Great efforts 



should be made to reduce this mortality to much lower levels. 

 Carter and Sealy (1984) pointed out two main methods of 

 reducing gill-net mortality: (1) exclude fishing from areas 

 with high murrelet densities at sea; and (2) allow daylight 

 fishing only, since most murrelets are caught in nets at night. 

 These solutions often may not apply to other seabird species. 

 Another factor affecting levels of mortality is the future of 

 these fisheries themselves, if fish stocks decline. However, 

 gill-net fishing is likely to continue at high levels due to 

 climbing value of salmon, limited entry of fishermen, and 

 constant fishing pressure during openings. It is clear that gill- 

 net mortality has the potential to be the greatest conservation 

 problem for Marbled Murrelets in Alaska since it occurs 

 annually throughout almost all at-sea foraging areas during 

 the breeding season when murrelets are aggregated. 



British Columbia 



Large salmon gill-net fisheries have existed off the mouth 

 of the Fraser River and in the Skeena River area since the 

 turn of the century. In the 1950s, other large fisheries 

 developed in other parts of British Columbia as the Fraser 

 fishery declined, due to severe landslides and other problems 

 upriver (Larkin and Ricker 1964). Small coastal fisheries 

 expanded with the development of a mobile fleet of gill-net 

 boats that travelled widely in relation to regulated openings. 

 The British Columbia gill-net and seine fishery is broken 

 down into 32 statistical areas and subdistricts (figs. 3 and 4). 

 Certain portions of these areas are closed to net fishing. Like 

 Alaska, open fishing periods vary considerably within areas 

 and districts. Gill nets used have a 1 15-mm minimum mesh 

 size and vary from 100-500-m length maximum (Department 

 of Fisheries and Oceans Canada 1978). 



Historical documentation of gill-net mortality of murrelets 

 and other seabirds in British Columbia is lacking. In 1979, 

 Marbled Murrelets were first reported in gill nets in Barkley 

 Sound on the west coast of Vancouver Island in Statistical 

 Area 23 (Carter and Sealy 1984, see below). It is likely that 

 gill-net mortality has occurred widely and for many decades 

 in British Columbia. Carter (unpubl. data) travelled widely 

 around the coast of British Columbia while conducting seabird 

 surveys in 1974-1977 (e.g., Campbell and others 1990, 

 Vermeer and others 1983). From 4-7 July 1976, he noted 

 two areas in the inside passage from Prince Rupert to Campbell 

 River where many gill-net fishing boats and Marbled Murrelets 

 co-occurred: (1) between Namu and Fairmile Inlet in Fitz 

 Hugh Sound in Statistical Area 8 (fig. 3; see brief reference 

 in DeGange and others 1993); and (2) in Johnstone Strait, 

 west of Port Neville, in Statistical Area 12 (fig. 4). Mortality 

 of murrelets probably has occurred in many areas of British 

 Columbia, but has not been properly documented, except in 

 Barkley Sound (below). 



In 1979 and 1980, Carter and Sealy (1984) documented 

 mortality of Marbled Murrelets in gill nets in Barkley Sound. 

 A total of 28 dead Marbled Murrelets (including 26 breeding 

 adults, 1 nonbreeder and 1 juvenile), 10 Common Murres and 

 1 Rhinoceros Auklet were recovered from 5 fishermen, a 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



275 



