Chapter 27 



Mortality of Marbled Murrelets in Gill Nets in North America 



Harry R. Carter 1 



Michael L.C. McAllister 2 



Abstract: Mortality of Marbled Murrelets (Brachyromphus 

 marmoratus) due to accidental capture in gill nets is one of the 

 major threats to murrelet populations. Gill-net mortality of 

 murrelets throughout their range has been occurring for several 

 decades and probably has contributed to declines in populations, 

 in conjunction with loss of nesting habitat and mortality from oil 

 spills. Gill-net mortality has been best studied in Prince William 

 Sound, Alaska, and in Barkley Sound, British Columbia. How- 

 ever, gill-net fishing occurs widely and it is likely that: (1) 

 several thousand to tens of thousands of murrelets are killed 

 annually in Alaska; (2) hundreds to thousands are probably killed 

 annually in British Columbia; and (3) tens to hundreds may be 

 killed annually in Washington. In the 1980' s, hundreds also were 

 killed in central California although recent regulations have mark- 

 edly reduced this mortality. Despite the potential impacts of gill-net 

 mortality on murrelet populations, little has been done to examine 

 the degree of mortality or to develop long-term solutions to 

 reduce or eliminate net mortality. Gill-net mortality should be 

 assessed by management agencies through the establishment of 

 more observer programs, especially in Alaska, British Columbia, 

 and Washington. 



Gill-net fisheries have occurred off the Pacific coast of 

 western North America throughout this century. Following 

 World War II, these fisheries expanded to cover large 

 geographic areas, including most nearshore and offshore 

 waters. Concern has been expressed repeatedly over the last 

 3 decades about the excessive mortality of seabirds and 

 marine mammals in gill nets in many areas of the North 

 Pacific Ocean (see reviews in DeGange and others 1993; 

 Jones and DeGange 1988; King 1984; King and others 1979). 

 Most attention has been paid to offshore international fisheries 

 where hundreds of thousands of seabirds are killed annually. 

 Less attention has been directed towards lower levels of 

 mortality in nearshore gill-net fisheries, even though this 

 mortality can have serious impacts to local seabird populations 

 (Atkins and Heneman 1987; Carter and Sealy 1984; DeGange 

 and others 1993; Piatt and Gould, in press; Piatt and others 

 1984; Takekawa and others 1990). 



There has been mounting concern about the impacts of 

 gill-net mortality on the Marbled Murrelet (Brachyramphus 

 marmoratus) (Carter and Morrison 1992, Carter and Sealy 

 1984, DeGange and others 1993, Marshall 1988a, Sealy 

 and Carter 1984). Murrelets become tangled and drown in 

 gill nets while swimming under water. Gill-net fishing is 

 conducted with either drift or set nets. Drift nets are operated 



1 Wildlife Biologist, National Biological Service, U.S. Department 

 of the Interior, California Pacific Science Center, 6924 Tremont Road, 

 Dixon, CA 95620 



2 Wildlife Biologist, Wildland Resources Enterprises, 60069 Morgan 

 Lake Road, La Grande, OR 97850 



3 Commercial Fisherman, 9229 Emily Way. Juneau. AK 99801 

 (Deceased June 1993) 



M.E. "Pete" Isleib 3 



from a boat and are free to move with the currents, whereas 

 set nets are anchored at both ends and can be set at any 

 depth. Other forms of net fishing tend to be much less 

 destructive to birds. Seine fishing is known at times to 

 cause mortality. 



At-sea mortality from gill nets and oil spills has been 

 identified as a significant conservation problem for the 

 Marbled Murrelet (Carter and Morrison 1992; U.S. Fish 

 and Wildlife Service, in press). Gill-net mortality may act 

 separately or in concert with the loss of nesting habitat 

 and mortality from oil pollution to threaten survival of 

 several populations. In this paper, we: (1) review factors 

 that lead to mortality of murrelets in gill nets; (2) discuss 

 known and suspected levels of mortality of Marbled 

 Murrelets in gill and seine nets throughout their range in 

 North America; and (3) indicate management actions that 

 have been considered to stop or reduce the impacts of gill- 

 net mortality. Information is presented by state and province 

 from north to south. Information for the three southern 

 states was collated for the Marbled Murrelet Recovery 

 Plan (U.S. Fish and Wildlife Service, in press.) 



Alaska 



Large net fisheries have existed in many areas of Alaska 

 for decades. These fisheries target mainly salmon 

 (Onchorynchus sp.), although other fish also are taken (e.g., 

 herring Clupea harengus). Salmon fisheries are broken 

 down into 12 statistical areas with many districts and 

 subdistricts in each area. The salmon gill-net fishery targets 

 specific stocks of fish as they return to rivers to spawn, and 

 can occur within 3 miles of land in a river, river delta, 

 embayment, or fiord. Open fishing periods vary between a 

 half day and 7 days per week, depending on run strength of 

 fish stocks, harvest levels, and numbers of fish reaching 

 spawning areas. Some districts are opened for only one 

 year out of five. 



Types of Nets 



Drift nets are about 900-1200 feet (275-365 m) long 

 and are fished as a single unit. Set nets are about 300-900 

 feet (90-275 m) long, but are usually broken down into 

 subunits as short as 60 feet (18m) long. Gill nets in most 

 areas are restricted to 60 meshes deep. In Bristol Bay, there 

 is a 28-meshes deep maximum for both set and drift nets. 

 Stretched mesh sizes vary from 4.5-9.0 inches (11.4-22.9 

 cm) although restrictions apply in certain districts and at 

 certain times. Thus, a net with a mesh size of 5.5 inches (14 

 cm), with 60 meshes, would be about 30 feet (9 m) deep. 

 When restrictions do not apply, nets are often set at 120-150 

 meshes deep. Further discussion of various aspects relating 



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



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