Burger 



Chapter 29 



Marine Distribution, Abundance, Habitats in British Columbia 



Trevor Channel - Cape Beale model 



1 2 



Distance from shore (km) 



Laskeek Bay 1 992 open water surveys (n = 5) 





1 2 



Distance from shore (km) 



Figure 6 Variations of the density of Marbled Murrelets with distance from shore, in exposed (upper) and 

 sheltered (lower) ;nshore waters in British Columbia. Upper: densities predicted by the logarithmic model derived 

 from Carter's (1 984) counts made in 1 980 in Trevor Channel and the Cape Beale area (see fig. 5). Lower: mean 

 densities in 200-m segments of open water surveys made in Laskeek Bay in 1 992 (Lawrence, pers. comm.). Error 

 bars show standard deviation. 



abundance, such as estimates using echosounders. Carter 

 (1984) explained the influx and aggregations of murrelets in 

 Trevor Channel. Barkley Sound, as a consequence of 

 aggregations of juvenile herring (Clupea harengus) and sand 

 lance. Murrelet distribution in this area was highly clumped 

 and was associated with features such as gravel or sand 

 substrates, where sand lance might burrow, or thermal fronts 

 and small channels, where juvenile herring and other prey 

 aggregate (Carter 1984, Carter and Sealy 1990). Carter (1984) 

 found that murrelets in Trevor Channel were more likely to 

 have food in their guts in the morning than in the afternoon 

 or at night, and linked this with the availability of sand lance 

 and juvenile herring in surface waters. Off Langara Island, 



where murrelets concentrated on euphausiids and sand lance, 

 the birds appeared to feed throughout the day (Sealy 1975c). 

 Availability of sand lance appeared to affect both the spatial 

 distribution and the seasonal densities of murrelets in Okeover 

 Inlet, Desolation Sound during the breeding season (Kaiser 

 and others 1991, Mahon and others 1992). 



The effects of El Nino and other oceanographic events 

 on murrelets in British Columbia are poorly known. 

 Exceptionally warm water persisted off southwestern 

 Vancouver Island from January through August 1992 and 

 again from April through mid-June 1993 (data from H. 

 Freeland, in Burger 1994). In Barkley Sound this warm water 

 was associated with an influx of mackerel (Scomber japonicus) 



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



303 



