Carter and others 



Chapter 27 



Mortality in Gill Nets 



to how murrelets become tangled in gill nets can be found in 

 Carter and Sealy ( 1984). 



Behavior Near Nets 



Isleib (1982) observed Marbled Murrelets feeding close 

 to nets, as well as elsewhere, but birds appeared to be displaced 

 by a vessel or activity aboard a vessel. Young of the year 

 showed little fear of vessels. Isleib usually observed murrelets 

 swimming along the nets in singles or pairs, frequently 

 diving, often surfacing on one side and then the other of the 

 net. This occurs with nets 60 feet (18m) deep, with mesh 

 sizes of 5.5 inches (14 cm). Isleib suggested that they may 

 actually be going through these nets, but more than 80 

 percent of the birds were caught at night. Isleib felt murrelets 

 are likely caught while pursuing small feed fishes, including 

 juvenile herring, sand lance (Ammodytes hexapterus), capelin 

 (Mallotus villosus), needlefish (Strongylura exilis), and 

 various salmon fry. This may not be the case for some of the 

 juvenile murrelet mortalities where juveniles tend to dive 

 from suspected danger on the surface while adults tend to 

 fly. Murrelets are caught at varying depths in the nets, from 

 the surface to 10 meters, mostly 3 to 5 meters down. Beyond 

 60 meshes deep, murrelets do not appear to be caught. 



Historical Records of Mortality: 1950s to 1980s 



Historical documentation of gill-net mortality of murrelets 

 (and other seabirds) in Alaska before the 1970s is poor. An 

 observer program for determining incidental mortality of 

 seabirds in offshore net fisheries in Alaska began in 1974 

 (King and others 1979), but a similar observer program for 

 nearshore waters, where murrelets primarily occur and are 

 killed, was not instigated by the National Marine Fisheries 

 Service until 1990 in Prince William Sound (DeGange and 

 others 1993, Mendenhall 1992, Wynne and others 1991). At 

 least 3 scraps of information indicate that gill-net mortality 

 occurred in the 1950s and 1960s: (1) Sealy and Carter (1984) 

 reported an adult murrelet in breeding plumage was killed at 

 a depth of 25-30 feet in a gill net near Little Port Walter on 

 Baranof Island in southeastern Alaska between 29 July and 6 

 August 1958 (Sealy, pers. comm.); (2) a molting murrelet 

 was reported killed in a fishing net at Coho Beach, in the 

 northern Gulf of Alaska, in August 1959 (Smith 1959); and 

 (3) two adults in breeding plumage were killed in gill nets 

 near Cordova, in the northern Gulf of Alaska, in 1969 (Carter, 

 unpubl. data in Mendenhall 1992). 



In the 1970s, the only documentation of mortality of 

 murrelets in gill nets in Alaska was obtained by one of us 

 (Isleib). Below we summarize the information and 

 observations, taken largely from a letter to the senior author 

 (Isleib 1982). Most of Isleib' s observations are from Statistical 

 Area E, the Prince William Sound/Copper-Bering River 

 Districts. Specific districts have different opening periods 

 by gear type. 



The number of murrelets that are killed is difficult to 

 determine. Isleib estimated that the degree of magnitude for 

 all the districts of Area E was "several hundreds" annually. 



He felt that the numbers had increased in the past 20 years 

 due to several factors: the vessels are continuously fishing 

 around the clock; the use of finer web; and more boats are 

 actively fishing (Isleib 1982). He observed that murrelets 

 are killed throughout the fishing season, with most (80+ 

 percent) killed at night. 



He felt that the major locations of kills were as follows. 

 In the Copper and Bering River Districts, murrelets are not 

 numerous, except during brief migration periods in early 

 September, and most birds occur offshore. These districts 

 front the open Gulf of Alaska. Here, most murrelets are 

 caught between 0.5 and 3 miles (0.3-1.9 km) offshore, where 

 water depth is about 10 fathoms (18 m). His best estimate of 

 murrelet mortality in these districts is from 100 to 300 

 annually. A similar number, or slightly higher mortality of 

 Common Murres (Uria aalge) also occurs here. 



In the Coghill-Unakwik and Eshamy districts, murrelets 

 were numerous in the 1970s: 10,000+ Kittlitz's Murrelets 

 (Brachyramphus brevirostris) and 100,000+ Marbled 

 Murrelets. These districts are either within or at the mouths 

 of fjords. Isleib estimated the annual kill at about 500 birds. 

 In the Bristol Bay area, murrelets are very rare. Isleib fished 

 Bristol Bay for 3 years and only 3 Common Murres were 

 killed in 1981. 



While the above observations apply mainly to the 1970s, 

 more recent comments by Isleib reflected similar or greater 

 amounts of mortality continuing throughout the 1980s (see 

 DeGange and others 1993). For southeastern Alaska, Isleib 

 had estimated in DeGange and others (1993) up to 1,000 

 Marbled Murrelets were taken annually, but it is unclear if 

 this estimate is based on more data than available in 1982. 

 At this time, he had "no first hand knowledge", but suspected 

 mortality at similar levels as found in Prince William Sound 

 (Isleib 1982). His suspicion was based on fishing effort, 

 fishing locations near murrelet aggregations, and types of 

 fishing gear (Isleib, pers. comm.). For the same reasons, he 

 suspected similar mortality along the Alaska peninsula during 

 the 1970s and 1980s (Isleib, pers. comm.). 



Isleib observed that murrelets are captured in the same 

 locations year after year throughout the season. Young of 

 the year, first noted in mid-July, are killed in a higher 

 proportion to their respective numbers than adults. 



Historical Records of Mortality: 1980s and 1990s 



From 1983-1993, one of us (McAllister, unpubl. data) 

 conducted surveys of murrelets throughout most coastal regions 

 in the Gulf of Alaska. Preliminary population estimates for 

 the Gulf of Alaska are similar to estimates generated more 

 recently from the Outer Continental Shelf Environmental 

 Assessment Program (OCSEAP)(Piatt and Ford 1993; Piatt 

 and Naslund, this volume). The sub-area found to support the 

 greatest populations (45,000-70,000 birds [McAllister, unpubl. 

 data]) is Southeast Alaska. Three major nesting areas (each 

 containing approximately 5,000-10,000 birds) occur in 

 southeastern Alaska: the west slopes of Admiralty Island; the 

 mainland slopes of Stephens Passage (Juneau south to Tracy 



272 



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



