SPRING 1974 



0.6 f 



0.4 

 0.2 



12/23 



11/19 ^ ^1'?9 



2/18 



0/13 0/14 



SPRING 1975 



9- 19- 28- 56- 111- 184- 



18 27 55 HO 183 366 



9- 19- 28- 56- 111- 184- 



18 27 55 110 183 366 



FISHERY BULLETIN: VOL. 85, NO. 2 



e/,g SUMMER 1975 



6 



SUMMER 1976 



10/23 



1/14 0/10 ^''^ 



FALL 1973 



13/18 



13/19 ^_ 5/1 2 



9- 19- 28- 56- 111- 184- 

 18 27 55 110 183 366 



DEPTH ZONES 



Figure 1.— Indices of relative abundance (Musick and McEacliran 1972) oiDecapterus pwnctatvs by depth zone from MARMAP trawl 

 survey for all cruises. Fractions are the number of trawls with round scad/total number of trawls. 



Table 2.— Surface and bottom temperatures where Decapterus 

 punctatus was collected in the South Atlantic Bight. Upper figure 

 of each pair is surface value, lower figure is bottom value; x = 

 mean, s = variance. 



Winter 



Spring 



Summer 



Fall 



1975 1976 1977 1974 1975 1974 1975 1976 1973 



mini- 

 mum 



maxi- 



17,4 

 17.2 



2.5 

 2.0 



13.3 

 13.3 



21.7 



mum 19.9 



19.1 

 17.0 



3.5 

 2.8 



12.1 

 12.3 



23.3 

 22.8 



17.9 

 16.4 



2.5 

 2.1 



11.5 

 11.6 



18.9 

 18.9 



19.6 

 19.1 



1.5 

 1.3 



17.4 

 17.0 



23.2 

 22.0 



18.7 

 17.4 



2.7 

 1.3 



14.9 

 14.9 



27.9 

 25.5 



0.5 

 1.9 



26.9 

 19.3 



28.1 

 25.4 



26.0 

 25.4 



23.8 

 23.7 



23.8 29.1 

 19.2 28.2 



winter. Catches over sponge-coral habitat were sig- 

 nificantly larger than catches over sandy habitat in 

 winter during 1976-77, whereas catches over the 

 two bottom types were similar in other seasons 

 (Table 3). Habitat types did not differ in tempera- 

 ture during either winter (Wilcoxon rank sum tests, 

 P = 0.25 and 0.20, df = 19 and 12, respectively). 

 Thus, temperature alone did not appear to account 

 for the observed difference in winter catches over 

 the two bottom types. 



Table 3.— Comparison of catches of Decapterus punctatus over 

 sponge-coral and sand habitats by cruise. If the Wilcoxon rank sum 

 (Z) is significant (*), the direction of the difference is indicated. 

 ZC; = sum of catches over sponge-coral habitats (n, = # trawls), 

 XCj = sum of catches over sand habitats (n^ = trawls). 



Cruise 



IC, 



ICc 



Winter 

 1975 

 1976 

 1977 



Spring 

 1974 

 1975 



Summer 

 1974 

 1975 

 1976 



Fall 

 1973 



3 



7,201 



10,936 



239 

 2 



445 

 614 

 663 



215 



(3) 

 (11) 

 (11) 



(11) 

 (6) 



(14) 



(18) 



(8) 



(10) 



672 



597 



39 



4,717 

 46 



8,023 

 4,805 

 5,094 



13,139 



(49) 

 (75) 

 (82) 



(91) 

 (34) 



(74) 

 (69) 

 (81) 



(77) 



0.23 



3.57* 



5.40* 



0.05 

 0.36 



0.61 

 0.92 

 0.86 



0.74 



(L>S) 

 (L>S) 



Round scad did not appear to undertake seasonal 

 longshore migrations in the South Atlantic Bight. 

 Catches north and south of lat. 31°30'N (which 

 roughly bisects the South Atlantic Bight) showed 

 occasional differences (Table 4), but no consistent 



254 



