FISHERY BULLETIN: VOL. 83, NO. 4 



and Flowers (1968) have reported, using a computer 

 program by Campbell et al. (1983). 



RESULTS 



Scallop Gear-Lobster Interactions 



1978 Study 



No scallops were present but lobsters were numer- 

 ous and were observed by divers to be frequently 

 foraging in the open. Average carapace length of 22 

 diver-collected lobsters was 61.3 mm (SD = 26.8). 

 While the microdistribution of substrate type was 

 patchy, tows were of sufficient duration to cover all 

 substrate types. Under the assumption of an average 

 uniform lobster density during tows, lobster catches 

 made by the Gulf sweep-chain drag over sand and 

 rock-sand were highest. Average catches in the lined 

 and unlined portion of the drag were 0.53 and 0.07 

 lobsters/m of drag width fished per min (m^^min^^), 

 respectively (Ikble 2). 



No lobsters were retained by the unlined rock 

 drags, but since they were retained in the back cover 

 of the drag, lobsters were entering the drag and 

 passing through the rings. These lobsters did not 

 show any external evidence of damage. The hoods 



Table 2.— Average number of lobsters caught 

 m~'min'' of drag width In the hoods and linings of the 

 scallop gear used in 1978. Each drag type was hauled 

 over both sand and sand-rock substrates off 

 Miminegash, Prince Edward Island. L = lined gear; 

 UL = unlined gear; H = hood; B = back cover. 



Drag type 



No. 

 tows 



Lobster catch 



UL 



H 



B 



Gulf sweep chain 5 0.53 0.07 0.15 0.31 

 Gulf rock drag 5 0.11 0.00 0.06 0.11 



Digby rock drag 6 0.02 0.00 0.07 0.04 



of all three drag types contained lobsters, indicating 

 that lobsters can escape by swimming over the ad- 

 vancing drag. 



1981 Study 



RELATIVE SCALLOP AND LOBSTER ABUN- 

 DANCE.— Catch results and sightings per tow 

 (Jamieson et al. 1981a) indicated that for each study 

 area, considerable variation existed in abundance of 

 both scallops (Fig. 3) and lobsters (Fig. 4). Substrate 

 type was variable over the distance of a single tow, 

 and this appeared to be a major factor influencing 

 relative scallop and lobster abundance. 



Scallop and lobster densities in the two areas (B 

 and C) fished for scallops varied significantly on 

 some dates (Tkble 3) from those densities in the non- 

 fished areas (A and A^); fished grounds had a greater 

 number of scallops, but fewer lobsters, than did the 

 nonfished ground. Between the two fished areas, the 

 only significant (P < 0.05) difference was in the 

 scallop drag catch in May, but study area C off Red 

 Head generally yielded more of both species than 

 did study area B off West Point (Figs. 3, 4). 



There were no significant differences (P > 0.05) 

 in the densities of either scallop or lobster in the non- 

 fished area between the two sampling periods. 

 Lobster sightings per tow in both fished areas were 

 significantly greater (P < 0.05) in July than in May, 

 but the number of sightings averaged less than in 

 the unfished area. Although not always significant, 

 the general seasonal trend of lobster abundance, as 

 indicated by the control sampling procedures, in- 

 creased between May and July in all areas. Scallop 

 catch decreased significantly (P < 0.01) in the ground 

 off Red Head between May and July. On fished 

 ground, average scallop density decreased whereas 

 scallop density on the nonfished ground increased 

 during this time period. 



Table 3. — Average scallop and lobster catch in a 4-gang Gulf rock drag in 1981, and the abundance per 1,000 

 m^ In each study area before the scallop drag was towed (control) and in the drag path behind the drag. Values 

 with asterisks are significantly different from the corresponding value in the nonfished scallop location. * = 

 P < 0.05; ** = P < 0.01; n = number of tows. 



580 



