FISHERY BULLETIN: VOL. 85, NO. 4 



was analyzed with respect to shell hardness and 

 carapace length (<81 mm vs. >81 mm). Size- 

 specific damage to newshell American lobsters 

 taken in the trawl fishery was significant with 

 smaller lobsters incurring more damage (43% vs. 

 30%, x^ = 6.64, P =0.01). There were no size- 

 specific differences in damage to newshell lob- 

 sters taken in the pot fishery or to hard-shelled 

 ones in either fishery. 



Trawled egg-bearing female American lobsters 

 (always hard shelled) incurred 1.9% major dam- 

 age, no immediate mortality, and 2.1% minor 

 damage throughout the sampling period 

 in = 909). Eggbearers >81 mm CL (n = 585) ex- 

 hibited 2.2% major damage and 2.4% minor dam- 

 age while those <81 mm CL (n = 306, 18 size 

 unspecified) incurred 1.3% major damage and 

 1.6% minor damage. Pot-caught eggbearers sus- 

 tained 0.9% major, and 0.8% minor damage 

 throughout the sampling period in = 1,926). One 

 of 1,926 pot-caught egg-bearers (0.05%) died on 

 deck. These data suggest that the damage and 

 immediate mortality to gravid American lobsters 

 associated with both fisheries is minimal. 



From September 1983 through December 1984, 

 trips were made with both large (15-26 m) and 

 small (12-14 m) trawl vessels during eight differ- 

 ent months. In two of those months, damage rates 

 were equal, in two they differed by <1%, and in 

 four they ranged from 7.3% higher for small ves- 

 sels to 13.7% higher for large vessels. The differ- 

 ence exhibited in the four months for which devi- 

 ations of more than 1% were observed was not 

 significant (x^ = 0.019, P < 0.5) indicating that 

 damage to trawled American lobsters is inde- 

 pendent of vessel size. 



Trawl-induced damage occurred at similar 

 rates in cold-water vs. warm-water intermolt pe- 

 riods (2.2% January-June vs. 3.1% August- 

 September) and between cooling and warming 

 postmolt periods (11.5% October-December vs. 

 12.6% July; Table 1). This suggests that damage 

 due to trawling is more a function of shell condi- 

 tion than water temperature. 



Delayed Mortality 



From November 1983 to August 1984, 526 



Table 3. — Estimated mortality to American lobsters <81 mm CL (delayed and imme- 

 diate) due to otter trawling in 1984. Actual delayed mortality is computed by multiplying 

 the percent occurrence of each damage category in trawl catches by the laboratory 

 delayed mortality rate for that category. Total mortality rate is the sum of the actual 

 delayed mortality plus immediate mortality observed on deck. 



fVlay {N = 608, trawler catches; N 

 Hardshell 



41 , laboratory samples) 



740 



