Fishery Bulletin 103(1) 



This study 

 NMFS 



Table 3 



Mean catch and landings per tow for scup and black sea bass-targeted tows. 



Target 

 Target 



10 

 6 



365.0 

 171.9 



278.7 

 170.1 



86.3 

 1.8 



0.31 

 0.01 



(P=0.0085), and 75 th (P=0.0038) percentile sizes and 

 the mean length (P= 0.0001) were significantly lower for 

 tows in which most scup were discarded (Fig. 3). When 

 the data sets were analyzed separately, our study found 

 that the 50 th (P=0.0133) and 75 th (P=0.0040) percentile 

 sizes and the mean length (P= 0.0338) were significantly 

 lower for tows where discards exceeded landings. Not 

 surprisingly, when fishermen caught larger scup, fewer 

 scup were discarded. In the NMFS observer data set, 

 no significant size effects were found for any of the 

 percentile fractions. 



When the discards and landings were analyzed sepa- 

 rately, the lengths of fish discarded did not differ be- 

 tween tows for which discards exceeded landings and 

 tows for which landings exceeded discards. However, for 

 the landed fish, the 50 th (P=0.0034) and 75 th (P=0.0018) 

 percentile sizes and the mean length (P=0.0033) were 

 larger for tows where landings exceeded discards 

 (Fig. 4). Discards decline when larger scup are propor- 

 tionately more abundant in the catch. 



We examined the influence of total catch (all species 

 combined) on the length-frequencies of scup in tows 



where scup landings exceeded or did not exceed scup 

 discards. For those tows with total catches below the 

 median catch, a significant effect was noted for the 

 median (P=0.0039), the 75 th percentile (P=0.0006), 

 and the mean (P=0.0288) length of scup. In those tows 

 where total catch weight was relatively low, the median, 

 mean, and 75 th percentile lengths were larger in tows 

 where scup landings exceeded discards. No significant 

 effects on the length-frequency distribution of scup were 

 observed for total catches that were above the median. 

 The analysis identifies a strong trend towards the land- 

 ing of larger-size scup in tows yielding total catches 

 below the median for all tows. 



Both landings and discards were affected in those 

 tows in which total catch fell below the median. For 

 landed scup, the median (P= 0.0062), the 75 th percentile 

 (P=0.0051), and the mean (P=0.0113) length were higher 

 in tows with total catches below the median when scup 

 landings exceeded discards. For those scup that were 

 discarded from tows with total catches below the me- 

 dian, a significant size effect was observed for the 75 th 

 percentile (P=0.0265). Discarded scup were larger in 



