MACDONALD ET AL.: FISH ASSEMBLAGES AND THEIR SEASONAL MOVEMENTS 



bottom station C were the most seasonally dynamic 

 (Fig. 12). Adult witch flounder and most hakes left 

 station B in winter for grounds further offshore in the 

 Gulf of Maine (Powles and Kohler 1970; Kulka and 

 Stobo 1 98 1), and this site was occupied by adult win- 

 ter flounder and longhorn sculpin, perhaps from 

 inside Passamaquoddy Bay or other adjacent 

 inshore sites (McCracken 1963). 



Superimposed on the two offshore, essentially 

 benthic fish assemblages was a seasonal semipelagic 

 component. In summer, silver hake was the 

 numerically dominant species. During fall, diversity 

 increased with the arrival of spiny dogfish, butterfish, 

 and American shad. In winter, Atlantic herring 

 numerically dominated the pelagic component at all 

 offshore sites (Fig. 12). 



Diversity, expressed simply as number of species 

 captured, varied appreciably at beach sites during 

 the year. Diversity was 2-5 species in winter-spring, 

 9-13 species in summer, and 4-6 species in fall-winter 

 (Fig. 13). Total number of species captured at 

 inshore sites was 35, compared with 51 species cap- 

 tured at offshore sites. 



Diveristy of assemblages at deep offshore sites 

 (80+ m) was more stable on an annual basis because 

 of the seasonal influx and departure of species from 

 and to adjacent habitats (Fig. 14). Species number 

 varied between 7 and 1 7 fishes at station B and 7 and 



20 fishes at station A, fluctuating about a mean of 1 2/ 

 sampling trip. During 1965, Tyler (1971) observed a 

 higher mean diversity of 17 species/ trip at station A 

 with a maximum occurrence of 24. The difference 

 between his observations and ours may be accounted 

 for partially by the decline in haddock abundance 



o 



5 



14 



12 - 



10 - 



8- 



Q. 

 CO 



~ 6 



2 - 



J J A 

 Month 



FIGURE 13.— Monthly diversity of fishes at intertidal stations 3 and 

 8 in Passamaquoddy Bay. Species/month for station 3 is mean of 

 1976 and 1977 samples. 



20 



16 



12 



2 



a 



CO 



Station A \ 



Station B 



' ' i i ' i i i i i i . i i i i i i i i i i i i i i i i  i 



F A J A O D| F A J A O D| F A J A 

 1976 1977 1978 



Figure 14.— Seasonal diversity of 

 fishes at station A (Passamaquoddy 

 Bay) and station B (Bay of Fundy). Ver- 

 tical bars represent the range among 

 replicated collections. 



01 — I — 1—1 — I — I — 1 — I — I I 1—1 ,_l I I 1 L_l I I I i i i 1 I I I I I l_l 



F A J A O D] F A J A O D| F A J A 

 1979 1980 1981 



135 



