FISHERY BULLETIN: VOL, 77, NO. I 



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5 6 7 8 9 10 11 12 13 14 IS 16 17 

 Bottom Temperature °C 



Fu:URE 3. — Bottom temperatures at 448 stations where Ameri- 

 can shad were collected during bottom trawl surveys, 1963-76, 

 Cape Hatteras. N.C.. to Nova Scotia. 



Table 2. — Total sampling effort, number of shad catches, and 

 percent catch frequency of shad at each bottom temperature 

 during bottom trawl surveys, 1963-76, Cape Hatteras, N.C., to 

 Nova Scotia. 



Bottom temperature 

 (C) 



Total no 

 of trawls 



Trawls witti shad 



1 



2 



3 



4 



5 



6 



7 



B 



9 



10 



11 



12 



13 



14 



15 



16 



17 



18 



19 



20 



21 



22 



23 



16 



104 



270 



567 



987 



964 



1,047 



997 



909 



750 



741 



739 



626 



333 



164 



71 



56 



41 



30 



29 



34 



19 



5 











7 



16 



41 



40 



55 



50 



45 



40 



54 



48 



37 



12 



3 











































2 59 



2 82 

 4 15 

 4 15 

 5,25 

 502 

 495 

 533 

 7 29 

 6 50 

 591 



3 60 

 1 83 





 

 

 

 

 

 

 



temperatures between 7" and 1.3°C, with the 

 greatest capture frequency at 11°C (Table 2). 



Ocean depths at stations with shad ranged from 

 20 to 340 m, but most of these stations (65'7f ) were 

 <100 m deep (Figure 4). Of the 527 successful 

 collecting stations, 269 iBW) occurred at depths 

 between 50 and 100 m. Since trawling effort dur- 

 ing U.S. spring and fall surveys was proportional 

 to the area of each depth interval (Table 3), the 

 number of shad catches within these depth strata 

 was amenable to chi-square analysis. A compari- 

 son between shad catches at each depth interval 

 and catches at all other depths combined indicated 



105 125 145 



Median Deplhlmt 



FIi;lirE 4. — Frequency of American shad catches with depth at 

 527 survey stations. 1963-76. Cape Hatteras, N.C., to Nova 

 Scotia. 



T.'iBLE 3. — Depth intervals within the survey area and as- 

 sociated shad catches during U.S. bottom trawl surveys. 1967- 

 76. Cape Hatteras. N.C., to Nova Scotia. 



•P--0.05. 

 ••P 01, 



that the greater capture frequency in the 56- 110 m 

 interval was highly significant (P<0.01); shad 

 catches at all other depths were significantly 

 fewer (P<0.05) than expected (Table 3). 



Spring surveys were conducted mainly in March 

 and April, accounting in part for the more fre- 

 quent collections during these 2 mo (Figure 5). In 

 March, shad were distributed along the Middle 

 Atlantic Bight. Most fish between Long Island, 

 N.Y., and Cape Cod, Mass., were taken in 60-200 

 m of water, many along the outer continental shelf 

 (Figure 5). Few shad occurred in <60 m of water 

 north of lat. 40°N, whereas most catches south of 

 Long Island were at depths <60 m. 



During the summer, shad were not captured 

 south of lat. 40'N (Figure 6). Forty-six collections 

 in July and August were made in two general 

 areas: the Gulf of Maine and southeast of Cape 

 Cod, near Nantucket Shoals. Mean depth at these 

 stations was 95 m, but ranged from 35 to 214 m. 

 Catches were distributed along the coastal margin 

 of the Gulf of Maine and the southern half of 

 Georges Bank; most trawling stations in the 

 deeper, central Gulf did not collect shad. 



October received the greatest trawling effort 

 during autumn surveys. Shad were again distrib- 



202 



