Fritz and Brown: Interactions between the Pacific cod fishery and Steller sea lions 



511 



Although a portion of the AE of the sampling area is 

 also critical habitat, the majority of it is not. Cod are 

 thought to move from the areas east and south of the 

 survey area to aggregate within critical habitat, partic- 

 ularly north of Unimak Island, for spawning (Shimada 

 and Kimura, 1994; Thompson and Dorn, 2002). Leslie 

 analyses were conducted on longline data collected from 

 1 January to 2 March in the AE of the survey area, and 

 on trawl data collected from 20 January to 21 March. 

 The longline data yielded a highly significant nega- 

 tive relationship between CPUE and cumulative catch 

 (P<0.000001), whereas the trawl data did not <P=0.65; 

 Table 5 and Fig. 6). 



Trawl fishery CPUE in the HSE area was not cor- 

 related with daily average vessel length for the pe- 

 riod 20 January-30 April 2001 (P=0.16; r 2 = 0.02; Fig. 

 8). The data from the analysis period 6 February-24 

 March are highlighted in Figure 8. Although there 

 was a significant linear relationship between vessel 



length and CPUE for this shorter period (P=0.004), 

 the correlation coefficient was low (r 2 = 0.16), indicat- 

 ing that daily average CPUE and vessel length were 

 poorly correlated. 



Discussion 



The bottom trawl survey point estimate of cod biomass 

 in the HSE area (31,312 t) is approximately twice the 

 values derived from analyses of fishery data (approxi- 

 mately 14,500 t). This is in part because the fishery 

 worked almost exclusively within the eastern two-thirds 

 of the HSE area. Restratifying the HSE survey yields 

 biomass estimates of 23,329 t for the eastern two-thirds 

 used by the fishery and 7983 t for the western portion. 

 The fishery-derived biomass estimates for the eastern 

 portion of the HSE survey area are within the 957c con- 

 fidence bounds on the survey estimate (12,846-33,812 t). 



