10 



Fishery Bulletin 103(1) 



Catch statistics — black sea bass 



During the winter scup season, black sea bass are legally 

 caught with 10.16-cm mesh codends in offshore waters. 

 A boat captain often will target scup and black sea bass 

 on the same trip, but will use different mesh codends. A 

 total of 12 black-sea-bass-targeted tows were observed 

 in our study and 6 black-sea-bass-targeted tows were 

 documented in the NMFS observer data set (Table 1). 



Length frequency — black sea bass 



Black sea bass length-frequency distributions were 

 highly significantly different (often P=0.0001) between 

 those fish landed and those discarded. The mean size of 

 discarded black sea bass from our study was 22.9 cm and 

 ranged from 18.4 to 25.4 cm. Fifty percent of the black 

 sea bass discarded fell between 22.1 cm (25 th percentile) 

 and 24.3 cm (75 th percentile). In contrast, the mean size 

 of landed black sea bass was 31.1 cm and ranged from 



25.4 to 40.9 cm. For black sea bass landed, fifty percent 

 of the fish were found between 28.6 cm (25 th percentile) 

 and 33.3 cm (75 th percentile). For the NMFS observer 

 data, the mean size of black sea bass discarded was 23.4 

 cm and ranged from 20.7 to 27.0 cm. Fifty percent of 

 the black sea bass discarded fell between 22.3 cm (25 th 

 percentile) and 24.7 cm (75 th percentile). The mean size 

 of landed black sea bass was 28.5 cm and ranged from 



24.5 to 34.0 cm. For landed black sea bass, fifty percent 

 fell between 25.0 cm (25 th percentile) and 31.5 cm (75 th 

 percentile). 



Codend and gear 



Nine tows were made with the composite codend and 

 three tows were made with the 11.43-cm legal mesh 

 codend in our study. For the NMFS observer data, all 

 six targeted tows fell into the 6.35-10.16 cm mesh-size 

 group that included the legal mesh size of 10.16 cm 

 (Table 1). 



We found no significant effects of codend mesh size 

 on the percentile length-frequency fractions of black 

 sea bass. We considered landed and discarded black sea 



bass separately for those tows with total catches above 

 and below the median and, once again, no significant 

 codend mesh-size effects were observed. The total num- 

 ber of tows, however, was small. A significant codend 

 mesh-size effect (P=0.0389) was observed for black sea 

 bass landed. Landings were higher with the larger 

 mesh codends (composite 10.16+11.43 cm codend and 

 the 11.43-cm codend) rather than with the sl0.16-cm 

 mesh codend (Table 7). The small number of total tows 

 with the larger codend mesh sizes (10.16+11.43 cm and 

 the 11.43 cm) is probably responsible for this difference 

 in landings rather than differences in net performance. 

 Gear effects (net types) were not determined because 

 only the box net was used. 



Discards-to-landings ratio 



Total mean catch per tow was 365 kg and total mean 

 landings per tow was 279 kg for the 10 tows in our study. 

 For the six directed tows in the NMFS observer data, 

 average total catch was 172 kg and average total land- 

 ings were 170 kg (Table 3). In black-sea-bass-targeted 

 tows, the black sea bass catch comprised 34.2% of the 

 total catch. The discards-to-landings ratio for black sea 

 bass was 0.230. Relatively few black sea bass were dis- 

 carded. Scup comprised 0.9% of the total catch in black 

 sea bass targeted tows. Less than one percent (0.4%) 

 of the scup catch in black-sea-bass-targeted tows was 

 discarded. 



We analyzed cases where black sea bass discards ex- 

 ceeded or were less than landings in tows where total 

 catch (all species combined) was above or below the me- 

 dian. For total catches above the median, a significant 

 size effect was noted for the median length (P=0.0040), 

 the 75 th percentile size (P= 0.0007), and the mean length 

 (P= 0.0026). Larger fish were present in tows where dis- 

 carding was lower (Fig. 5). No significant effects on the 

 size distribution of black sea bass were observed in tows 

 with total catches below the median. We further divided 

 the catches above the median into discards and land- 

 ings. For those black sea bass that were landed from 

 tows with total catches above the median, a significant 

 size effect was observed for the 25 th (P=0.0199), the 



