SEA SCALLOP FISHING IMPACT ON AMERICAN LOBSTERS IN 



THE GULF OF ST LAWRENCE 



G. S. Jamieson' and A. Campbell^ 



ABSTRACT 



Damage to American lobsters, Homarus americanus, in Egmont Bay and off Miminegash, Price Edward 

 Island, is minimal from the drags of the seasonal sea scallop, Placopecten magellaniciis, fishery. During 

 May 1981, when commercial sea scallop fishing was occurring, American lobster abundance was low in 

 areas of profitable scallop exploitation. Sea bed substrate in these areas was generally smooth and most 

 lobsters were able to avoid the gear. In the areas with and without commercial scallop fishing, 1.3% and 

 11.7% of observed lobsters, respectively, were injured or retained by the drag. Lobster abundance in the 

 areas commercially exploited for scallops in May and June was significantly greater in July than in May, 

 but whether this was a result of a natural seasonal movement of lobsters or the cessation of scallop fishing 

 is unclear. 



Sea scallop, Placopecten magellanicus, and American 

 lobster, Homarus americanus, populations are fully 

 exploited in Northumberland Strait, Gulf of St. 

 Lawrence (Wilder 1947, 1965; Robinson 1979; 

 Jamieson et al. 1981c; Campbell and Mohn 1983). In- 

 dividual fishermen frequently fish both species, com- 

 monly in the same general area, although the 

 fisheries are separated temporally (Jamieson et al. 

 1981c; Conan and Maynard 1983). Recently, localized 

 low abundance of these important, commercial 

 species has heightened long-held convictions by 

 fishermen of the negative impact of sea scallop 

 fishing on American lobster stocks. Fishermen's con- 

 cern became acute for the Egmont Bay area during 

 1980, coincident with the discovery and exploitation 

 of new nearshore scallop concentrations near West 

 Point, Prince Edward Island (Fig. 1). Decreased 

 scallop recruitment in recent years (Jamieson et al. 

 1981b, c) has resulted in a scarcity of scallops in 

 traditional fishing areas, causing increased ex- 

 ploration for commercially exploitable scallop 

 concentrations. 



The magnitude of scallop gear-lobster interaction 

 is dependent on the spatial and seasonal distribu- 

 tions of scallops and lobsters and the impact of 

 scallop gear on commercial lobster abundance where 

 the distributions of both species overlap. Scallops are 

 widespread in Northumberland Strait (Caddy et al. 

 1977), but commercial concentrations are found only 



'Department of Fisheries and Oceans, Fisheries Research 

 Branch, Halifax, Nova Scotia; present address: Pacific Biological 

 Station, Nanaimo, British Columbia V9R 5K6, Canada. 



^Department of Fisheries and Oceans, Atlantic Biological Sta- 

 tion, St. Andrews, New Brunswick, EOG 2X0, Canada. 



in limited areas. The precise locations of these areas 

 are undocumented, and since they vary with time, 

 they cannot be predicted with any accuracy. However, 

 commercial log data has shown the broad distribu- 

 tion of scallop concentrations in Northumberland 

 Strait during 1979-80 (Jamieson et al. 1981b, c). 



The seasonal abundance and distribution of 

 commercial-sized lobsters is largely unknown, but 

 their general distribution overlaps that of scallops 

 (Stasko et al. 1977; Conan and Maynard 1983). There 

 have been few field studies conducted on lobsters in 

 this area: Ibmplemann (1933, 1934, 1935, 1936) 

 reported on lobsters and the fishery in Northumber- 

 land Strait; Wilder (1963) and Wilder and Murray 

 (1956) reported on movements and growth of tag- 

 ged lobsters liberated in Egmont Bay. 



Scallop and Irish moss, Chondrus crispus, drags 

 can damage lobsters, although lobsters exposed on 

 open ground tended to avoid moving drags. Most 

 gear-induced damage has resulted from lobsters in 

 burrows being hit or crushed by rocks disturbed by 

 the drag (Scarratt 1973, 1975; Pringle and Jones 

 1980). 



Investigations reported here document 1) the 

 scallop drag/lobster interactions off Miminegash, 

 Prince Edward Island, during August 1978 and in 

 Egmont Bay during May and July 1981; and 2) the 

 relative abundance and movement of lobsters trap- 

 ped and tagged in Egmont Bay prior to (June-July 

 1981) and during the lobster fishing season (10 

 August-10 October 1981). Lobster abundance may 

 change relatively rapidly because of their potential 

 high mobility. Therefore it is important to charac- 

 terize lobster microdistribution and assess the con- 



Manuscript accepted January 1985. 

 FISHERY BULLETIN: VOL. 83, NO. 4, 1985. 



575-81^ 



