382 



Fishery Bulletin 100(2) 



71,0 70.5 70,0 69,5 69,0^„.--^8.5 68,0 67.5 67 66 5 \66,0 65,5 



21 June 2000 22 June 2000 



Figure 1 



The northeast U.S. continental shelf region, with scallop fishing fleet activity i  I in 

 closed area II of Georges Bank on 21-22 June 2000 overlaid with the sampling sites 

 I ▲ I occupied by the NOAA FRV Albatross IV i Cruise AL 00-0.3 ). 



lop viscera in the diets of longhorn sculpin. among other 

 species, and undertook extra samphng of sculpin stomachs 

 to assess the magnitude of this phenomenon. We also un- 

 dertook extra samphng of sculpin at the other two sta- 

 tions. We present mean stomach volume and mean percent 

 (by volume) diet composition for longhorn sculpin at these 

 four stations. 



To determine the prevalence of this phenomenon and 

 whether discarded scallop viscera are a regular food sub- 

 sidy that significantly influences the sculpin population, 

 we examined the stratified mean number of sculpin per 

 tow on Georges Bank (Azarovitz, 1981). We calculated this 

 index of abundance across the fall bottoni-trawl survey 

 time series from 1963 to 1998. Additionally, we examined 

 the mean stomach contents (cm'), maximal stomach con- 

 tents, percent frequency of occurrence of bivalve, inollusk, 

 or pectinid viscera, and an index of gorge feeding on an 

 annual basis from the food habits time series (Link and 

 Almeida, 2000). The index of gorge feeding (or more sim- 

 ply, the gorge index) was calculated as the percent of stom- 

 achs examined with total stomach contents greater than 

 10 cm'. We executed a simple linear correlation between 



the sculpin food-habit metrics and the index of abundance 

 to determine if any significant relationship exists between 

 gorge feeding and sculpin population abundance. 



Results 



On 21 and 22 June 2000, scallop fishing clearly occurred 

 at stations 8B and 7E, whereas no scallop fishing occurred 

 at 7D or 8E (Fig. 1 ). Rock crabs (both Cancer irroratus and 

 C. boreal is) and small crustaceans typify the diet of long- 

 horn sculpin (Fig. 2). However, at stations in areas with 

 scallop fishing activity, the diet of sculpin was predomi- 

 nately made up of scallop viscera. Crabs and small crusta- 

 ceans were still a part of the diet at those stations, but did 

 not comprise as large a percentage as was found at non- 

 dredged stations. 



The volume of food in sculpin stomachs was also an or- 

 der of magnitude higher at stations with intense scallop 

 fishing activity (8B=38.7 cnr' ±6.9; 7E=19.4 cnr' ±12.7) 

 than at those with no scallop fishing (8E=1.7 cm'^ ±1.4; 

 7D=0.3 cm' ±0.1). When scallop remains were present at 



