MACDONALD ET AL.: FISH ASSEMBLAGES AND THEIR SEASONAL MOVEMENTS 



It may be a response to avoid warm temperatures 

 (Olsen and Merriman 1946). Movement of ocean 

 pout is generally thought to cover only short dis- 

 tances (Orach-Maza 1975; Sheehy et al. 1977). 



Other blennioids occurred infrequently at station A 

 (Table 2). Selectivity of our shrimp trawl may have 

 been a factor in these low catches. One species, 

 radiated shanny, Ulvaria subbifurcata, which was 

 thought to be rare in Passamaquoddy Bay (Leim and 

 Scott 1966), was often captured (5/tow) at station A 

 during winter. Scuba searches during summer 

 revealed radiated shanny were abundant inshore, 

 under rocks in 6-9 m of water (Dadswell and Melvin, 

 pers. obs.). 



Five species of skate were captured during the 

 study (Table 2): Two species, thorny skate, Raja 

 radiata, and smooth skate, R. senta, were common, 

 regular components of the offshore site in the Bay of 

 Fundy; two little skate, R. erinacea, and winter skate, 

 R. ocellata, were regular components of station A in 

 Passamaquoddy Bay; and one species, the barndoor 

 skate, R. laeuis, was encountered occasionally at sta- 

 tion B. The species cooccurrences of skates and their 

 habitat selection are as described by McEachran and 

 Musick (1975). Some seasonal movement into 

 Passamaquoddy Bay was exhibited. Abundance of 

 smooth and thorny skates at station A increased dur- 

 ing summer and declined after late fall. Juveniles of 

 thorny, little, and winter skates were often captured 

 at beach sites during summer (Table 3). 



Several smaller fishes were captured at inshore 

 sites only, but again this may be an artifact of sam- 

 pling gear. Threespine stickleback, Gasterosteus 

 aculeatus, was a regular component at most beach 

 sites (Table 4). Other sticklebacks were more or less 

 confined to estuarine areas (Table 3). Mummichog, 

 Fundulus heteroclitus, and Atlantic silversides, 

 Menidia menidia, occurred mainly in estuaries during 

 summer but were part of the winter community at 

 beach sites (Table 4). 



Assemblages and Diversity 



Species assemblages in the study area varied 

 according to site and season. If juveniles and adults 

 of some dominant species are considered as separate 

 taxonomic units (Table 2), calculated coefficients of 

 community show similarity between similar habitat 

 types (e.g., soft bottom) at a given season, and be- 

 tween the summer assemblage of one habitat and the 

 winter assemblage of the next seaward habitat 

 (Table 5). In general, movement of assemblages was 

 from inshore in summer to offshore in winter with 

 some return movement in spring (Fig. 12). Some 

 species, however, exhibited a partial reverse of this 

 pattern (Atlantic tomcod, ocean pout). 



Specific groupings of fish were segregated among 

 the available habitats according to season. The "es- 

 tuarine" assemblage was dominated by warmwater, 

 euryhaline species, including sticklebacks, Atlantic 

 silversides, mummichogs, and juvenile clupeids. 

 Most of this group moved to adjacent, inshroe marine 

 habitat in winter (Tables 3,4), but Atlantic tomcod 

 and American smelt moved in the reverse direction to 

 form a winter estuarine group (Table 3). 



The summer "beach" assemblage consisted of 

 regulars such as threespine stickleback and rock gun- 

 nel and a summer component including juvenile 

 gadids, juvenile sculpins, flounders, and juvenile 

 alosids. Juvenile gadids (pollock, white hake, and 

 Atlantic tomcod) were most abundant in early sum- 

 mer but were replaced by steadily increasing num- 

 bers of clupeids in late summer (Fig. 5). Numerous 

 other postlarval and juvenile fishes, including four- 

 beard rockling and lumpfish, Cyclopterus lumpus, 

 appeared in the beach zone during the summer 

 (Table 3). In late fall, most of this assemblage left the 

 beaches and occupied offshore sites in Passama- 

 quoddy Bay. Atlantic herring concentrated at the 

 soft-bottom station C and the gadids, sculpins, and 

 winter flounder (juveniles) at the hard-bottom sta- 

 tion A. Threespine stickleback and rock gunnel 



Table 5. — Coefficients of community among seasonal fish assemblages in the lower Bay of Fundy. 



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