"To Hit et al.: Sizes of walleye pollock consumed by Eumetopias jubatus 



527 



plication of our DCFs to all structures in good and fair 

 condition increased the estimated mean mass of pollock 

 consumed by 88% (from a mean of 388 g to 731 g). 

 Thus, although we estimate that 44% of the number of 

 pollock eaten by Steller sea lions were adults, based on 

 length, their contribution, based on weight, increased 

 to 74%. In contrast, the contribution of juvenile fish (in 

 terms of mass) dropped to <0.1% (compared to <2% by 

 number). 



Geographical and temporal variation in sizes of 

 pollock consumed 



More pollock elements in good and fair condition were 

 recovered from inside haul-outs (?? = 567) than from sites 

 on the outside coastline (n = 342) (Table 1). Upon investi- 

 gation, we found the size of pollock consumed by Steller 

 sea lions varied over time and across regions (Fig. 3). 

 In particular, the frequency of occurrence of pollock 

 stage classes differed significantly in the scats of sea 

 lions resting at rookeries on the outside coastline of 

 Southeast Alaska in summer (mean FL=48.4 cm, n = 328, 

 modal range: 44-50 cm, 95% CI = 46.5-50.2, n s =126 

 scats) compared to those collected between October and 

 May at haul-outs in the waters of the inside passages 

 (mean FL = 38.4 cm, /; = 499, modal range; 30-34 cm, 



95% CI=36.9-40.3, n s =168 scats) (^=45. 2, P<0.001). 

 Scats from these inside haul-outs contained a greater 

 diversity of stage classes, and there was an equal prob- 

 ability of any given scat containing adults (51.2%), sub- 

 adults (47.6%). and adolescents (53.0%), but a far less 

 probability of containing juveniles (6.5%). In contrast, 

 the pollock found in scats from the outside rookeries 

 contained mostly adults (73.8%) and fewer occurrences 

 of the remaining three stage classes (38.1%, 9.5%, and 

 3.2%. respectively). Notably, the stage-class compar- 

 ison of summer 1999 with scats from inside versus 

 outside waters was not significant (Fishers exact test, 

 P=0.11). 



Similar proportions of each pollock stage class were 

 found in scats collected between years (Forrester, 

 Fisher's exact test, P=0.54; Hazy, Fisher's exact test, 

 P=0.16), and between rookeries (1994 only, Fisher's ex- 

 act test, P=0.57; all years, Fisher's exact test, P=0.22). 

 Scats from inside haul-outs collected in spring 1996 

 contained comparatively smaller fish than in other 

 months and years examined (Fig. 3). However, there 

 were no significant monthly differences in the pro- 

 portions of age classes from October 1995 to Febru- 

 ary 1997 (* 2 = 16.52, P=0.28) or when all monthly data 

 (June and July 1999) were included from inside haul- 

 outs (/=23.4, P=0.10). 



