Burger 



Chapter 29 



Marine Distribution, Abundance, Habitats in British Columbia 



Table 3 Density estimates (birds per linear km) of Marbled Murrelets at four 

 nearshore sites in the Queen Charlotte Islands surveyed in May-June 1977 

 and again in spring or summer 1990, 1991 or 1992. See appendix 1 for details 



Murrelet carcasses were rarely found in surveys of beached 

 birds in southern British Columbia, and were not among the 

 small sample of birds killed by chronic oiling but could 

 easily have been overlooked (Burger 1993b). 



Other Toxic Chemicals 



High levels of polychlorinated biphenyls (PCBs), dioxins, 

 and furans have been found in some piscivorous birds in 

 inshore waters of British Columbia, although Marbled 

 Murrelets were not sampled (Elliott and Noble 1993). Levels 

 of these contaminants and of organochlorides appear to be 

 declining in water birds sampled in British Columbia (Elliott 

 and Noble 1993, Elliott and others 1992). 



Gill Nets 



Little is known about the effects of gill nets on seabirds 

 in British Columbia. In 1988, the gill-net effort totaled 54,770 

 net-days, concentrated in summer and fall in inshore areas 

 (Barlow and others 1990). Anecdotal evidence from fishermen 

 suggests that Marbled Murrelets are among the bird species 

 most often killed. Carter and Sealy (1984) estimated that the 

 bycatch of 200 Marbled Murrelets caught in gill nets in 

 Barkley Sound in 1980 represented a loss of 7.8 percent of 

 the expected fall population (including loss of fledglings 

 caused by deaths of parent birds). There have been no other 

 studies of this problem in British Columbia, but it clearly 

 needs to be examined in detail. 



Other Effects of Fishing and Aquaculture 



Competition with the fishing industry for prey species 

 does not appear to be a significant issue for murrelets in 

 British Columbia. The herring stocks appear to have recovered 

 after periods of overfishing in the 1960's and are now strictly 

 regulated. Sand lance, zooplankton, and other prey species 

 are not fished in appreciable amounts. Sport fishing continues 

 to increase, and disturbance from the hundreds of small 

 boats, plus occasional bycatch of murrelets on lures is possibly 

 a localized problem. 



Habitat degradation and disturbance at fish and shellfish 

 pens can affect Marbled Murrelets, and many aquaculture 

 farms exist or are planned in sheltered inshore waters favored 

 by murrelets (e.g., Clayoquot, Barkley, and Desolation 

 sounds). Marbled Murrelets were not among the species 



considered to be most affected by aquaculture in British 

 Columbia (Rueggeberg and Booth 1989). 



Conclusions 



Proper management of the Marbled Murrelet in British 

 Columbia requires an improved estimate of the provincial 

 population and better understanding of its distribution and 

 relative abundance in the breeding and nonbreeding seasons 

 (Kaiser and others 1992). The census coverage of marine 

 areas has greatly increased over the past decade, but 

 quantitative surveys are still lacking for large tracts of the 

 convoluted 27,000-km coastline (fig. 4). The differences in 

 distribution between exposed and sheltered waters (e.g., fig. 

 6) and the variability within and among seasons (e.g. fig. 7 

 and 8) make it very difficult to estimate regional populations 

 from single-season shoreline transects. We need to know a 

 lot more about the factors which affect the murrelet's marine 

 distribution, such as prey distribution and effects of tides, 

 sea temperature, salinity, and seafloor topography, before 

 we can plan and interpret census transects and monitor 

 population dynamics. Regularly repeated surveys made over 

 many years, such as those performed in Laskeek Bay and 

 Barkley Sound, will be very valuable in showing both short- 

 and long-term patterns. 



Most of the urgent gaps in our knowledge can be filled 

 by relatively simple, inexpensive studies of fine-scale 

 distribution and foraging ecology if they are carefully planned 

 to collect the most pertinent data. There are also opportunities 

 to tap the expertise of the burgeoning number of birders and 

 naturalists who visit remote coastal areas of British Columbia. 

 The establishment of a long-term data base, meshed with a 

 Geographic Information System, would facilitate the 

 accumulation of data from both dedicated and opportunistic 

 censuses. Other priority problems, such as making a province- 

 wide marine census, measuring population demographics, 

 or investigating the effects of gill nets or logging, require 

 more dedicated, expensive studies. 



Acknowledgments 



Preparation of this chapter was funded by the British 

 Columbia Ministries of Forests (Research Branch) and 

 Environment, Lands and Parks (Wildlife Branch), and I thank 

 Brian Nyberg and Don Eastman for their support. I thank 

 Dick Brown, Rick Burns, Tony Gaston, Gary Kaiser, Anne 

 Harfenist, Moira Lemon, Ken Morgan, and Lynne Prestash 

 for valuable comments. Unpublished material was provided 

 by Rick Burns, James Clowater, Brian Fuhr (Wildlife Branch), 

 Bob Hanson (Pacific Rim National Park), John Kelson 

 (Conservation International), the Laskeek Bay Conservation 

 Society, Andrea Lawrence, Lynne Prestash, Anne Stewart 

 (Bamfield Marine Station), and Anne Harfensit, Gary Kaiser, 

 and Moira Lemon of the Canadian Wildlife Service. A special 

 thanks to Andrea Lawrence for assistance in analyzing the 

 Laskeek Bay data and with many other parts of the chapter. 



308 



USDA Forest Service Gen. Tech. Rep. PS W- 152. 1995. 



