To Hit et al.: Sizes of walleye pollock consumed by Eumetopias /ubatus 



523 



58 N 



56 



A 



50 



Petersburg 



" 14- 



15 



fh. r 



50 



Kilometers 



Pollock trawl 

 19 ' Dixon ,lsher V 



Entrance 



138 W 



134 



130 



Figure t 



Location of Steller sea lion (Eumetopias jubatus) haul-outs and rookeries visited during 

 1994-99 to collect scats containing pollock hard remains. Symbols: haul-outs in inside 

 waters (•), haul-outs in outside waters (©), haul-outs where scats were not collected or 

 sites at which no pollock hard remains were found (O), rookeries  and cities (*i. 



and Goodwin 1 ). We sought to compare the sizes of pol- 

 lock consumed in the 1990s with these earlier samples, 

 as well as with the sizes consumed by the declining 

 population of sea lions in the Gulf of Alaska and Ber- 

 ing Sea during the 1970s and 1980s (e.g., Pitcher, 1981; 

 Merrick and Calkins, 1996) and between 1998 and 2000 

 (Zeppelin et al., 2004, this issue). We also wanted to 

 evaluate the use of digestion correction factors (DCFs) 

 and skeletal structures other than otoliths to estimate 

 prey size, and to compare the different size estimates 

 for fish consumed by sea lions in Southeast Alaska 

 with sizes of fish caught by a nearby commercial trawl 

 fishery. 



Materials and methods 



Estimating sizes of pollock consumed 



Scats that contained pollock hard remains were collected 

 from four rookeries and 16 haul-outs from both inside 

 and outside waters of Southeast Alaska between 1994 



and 1999 (Fig. 1 and Table 1). Scats from three haul- 

 outs and four rookeries in outside waters were collected 

 from May through October 1994-99, but most were 

 collected from June and July. Scats from inside waters 

 were collected at 13 haul-outs located in the straits 

 and sounds between Juneau and Petersburg, Alaska 

 (56.8-58.6°N, 132. 8-134. 9°W) (Fig. 1). The majority of 

 these "inside" scats were collected from Frederick Sound 

 (Fig. 1) between October 1995 and February 1997. Most 

 were collected in the winter and spring, but some were 

 collected in the summer of 1999 (Trites et al. 3 ). In gen- 

 eral, the haul-out sites visited to collect scats were those 

 with relatively high numbers of animals across South- 

 east Alaska (Calkins et al., 1999; Sease et al., 2001). 



Scats were washed and sieved (0.5 mm) and hard 

 remains were identified by Pacific IDentifications Inc. 

 (Univ. of Victoria, Victoria, B.C.). Seven commonly 



3 Trites, A. W., D. G. Calkins, and A. J. Winship. 2003. Unpubl. 

 data. Marine Mammal Research Unit, Fisheries Centre, 

 University of British Columbia, Room 18, Hut B-3. 6248 Bio- 

 logical Sciences Rd., Vancouver, B.C., Canada, V6T 1Z4. 



