THE EFFECTS OF BOTTOM TRAWLING ON AMERICAN LOBSTERS, 

 HOMARUS AMERICANUS, IN LONG ISLAND SOUND 



Eric M. Smith and Penelope T. Howell' 



ABSTRACT 



American lobsters taken in the commercial trawl fishery in Long Island Sound, U.S.A., were in- 

 spected for incidence of damage and immediate mortality associated with bottom trawling. Similar 

 sampling was conducted in the pot fishery. American lobsters from trawl and pot catches were held 

 in controlled conditions for 14 days to determine the level of delayed mortality associated with the two 

 fisheries. Trawl-caught lobsters were exposed to subfreezing (-9.5°C) temperatures for periods from 

 30 to 120 minutes and then returned to seawater to determine the rate of freeze-induced mortality. 

 Major damage rates due to trawling ranged from 12.6-14.0% during molting periods to 0-5.6% during 

 intermolt periods. Delayed mortality ranged from 19.2% during the July molt to 1% during August 

 and appeared to be related to the incidence of damage, molt condition, and temperature. Mortality of 

 American lobsters held in subfreezing temperatures occurred after 30-minute exposure and reached 

 100% at 120-minute exposure. 



The American lobster, Homarus americanus, 

 supports one of the most valuable commercial 

 fisheries in the northwest Atlantic Ocean with 

 landings of approximately 20,900 t per year val- 

 ued at $115 million (Anonymous 1985). The fish- 

 ery is conducted predominantly with traps or pots 

 and, secondarily, with bottom trawl nets. 



Long Island Sound is a 2,908 km^ embayment 

 of the Atlantic Ocean in southern New England, 

 lying between Connecticut and New York at ap- 

 proximately lat. 41°N. The Sound supports a 

 spawning stock of American lobsters and a valu- 

 able commercial lobster fishery, which, in 1985, 

 generated landings of 1,134 t valued at $7.0 mil- 

 lion for some 900 commercial fishermen. In Con- 

 necticut, over 907^ of the commercial landings are 

 taken by the pot fishery, and over 90^^ of Connect- 

 icut's commercial fishermen are lobster pot fish- 

 ermen. Connecticut trawlers, who catch Ameri- 

 can lobsters in a mixed species bottom fishery, 

 take <109c of Connecticut commercial landings 

 and constitute about 10% of all commercial fish- 

 ermen taking lobsters. Recreational lobstermen, 

 both potters and scuba divers, totaled 2,440 in 

 1985 but only accounted for about 5% of total 

 landings (CT DEP2). 



The resource is heavily exploited with annual 

 exploitation rates ranging from 85 to 959c (Briggs 

 1985; Blake 1986). Principal management mea- 



1 Bureau of Fisheries, Connecticut Department of Environ- 

 mental Protection, P.O. Box 248, Waterford, CT 06385. 



2Connecticut Department of Environmental Protection (CT 

 DEP) unpublished fishery statistics. 



sures include prohibitions on the taking of fe- 

 males bearing external eggs and the retention of 

 any American lobster <81 mm carapace length 

 (CD. These measures are intended to protect 

 American lobsters from exploitation until they 

 have reproduced at least once. 



During late 1982, commercial catch per unit 

 effort rates doubled from those of the previous 5 

 years (CT DEP fn. 2). This increase stimulated a 

 shift in directed fishing by some trawlers from 

 mixed finfish to lobsters. The redirection of effort 

 also generated competition for lobsters and fish- 

 ing space, and an extremely emotional contro- 

 versy arose between potters and trawlers. This 

 paper addresses the resource considerations of the 

 controversy, that is, the impacts of mobile trawl 

 gear on lobsters. 



This study was designed to measure 1) the 

 physical injury and immediate mortality in- 

 curred by American lobsters in the trawl fishery; 

 2) the potential level of trawl-induced delayed 

 mortality of American lobsters less than the min- 

 imum length upon return to the water; and 3) the 

 rate of mortality of American lobsters due to ex- 

 posure to subfreezing air temperatures during 

 winter fishing. 



METHODS 



Incidence of Damage 



Biologists made 63 trips aboard commercial 

 stern trawlers from 12 to 26 m and 12 trips on pot 

 vessels from 12 to 14 m. Except during January 



Manuscript accepted June 1987 



FISHERY BULLETIN: VOL. 85, NO. 4. 1987. 



737 



