FISHERY BULLETIN: VOL. 82, NO. 1 



since 1965 and the recent absence of American 

 plaice from this site, and partially by his use of a 0.6 

 cm cod end liner, which would have retained small, 

 occasional species more often than our 2.5 cm cod 

 end. 



Highest diversities occurred during winter at sta- 

 tion B and during summer at station A (Fig. 14) as a 

 result of seasonal exchange between these sites and 

 the arrival of periodics. The highest diversities record- 

 ed during the study period occurred at station A dur- 

 ing the fall, coinciding with maximum annual 

 temperatures (Fig. 2). Diversity at station C, the mid- 

 depth site, decreased from 13 species in May 1978 to 

 4 species in May 1980, perhaps in response to a 

 general decline in lower Bay of Fundy temperatures 

 during the study period (Fig. 3). 



GENERAL DISCUSSION 



Most authors have related the occurrence and dis- 

 tribution of adult benthic fishes in the North Atlantic 

 to substrate type and temperature (Edwards 1965; 

 Colton 1972; McEachran and Musick 1975; Scott 

 1976) and have shown that there is a marked seasonal 

 variation (Lux and Nichy 1971; Jeffries and Johnson 

 1974). Our findings agree and suggest yearly dif- 

 ferences at the same site for a given time may be 

 influenced mainly by annual ocean climate pertuba- 

 tion. Species occurrence and abundance appeared to 

 change in response to seemingly small changes in 

 temperature. Jeffries and Johnson (1974) reported a 

 similar observation concerning winter flounder 

 abundance over a 7-yr period in Narragansett Bay. 

 Pelagic and semipelagic species (Atlantic herring, 

 silver hake) demonstrated little or no substrate pref- 

 erence. Occurrence was apparently related to annual 

 migratory behavior. 



Seasonal movements of the various species was 

 largely from an inshore, shallow-water locality in 

 summer to an offshore, deepwater locality in winter 

 with a reverse movement occurring in spring. Cause 

 of this movement may have a large physiological com- 

 ponent related to temperature effects on the 

 osmoregulation of marine fishes (Potts and Parry 

 1964). In the southern part of their range, fish such as 

 winter flounder migrate onshore in winter (Bigelow 

 and Schroeder 1953) in response to availability of 

 preferred temperature but never encounter the low 

 temperatures found at northern latitudes. Atlantic 

 tomcod, a species known to produce an antifreeze in 

 its blood (Fletcher et al. 1982), was one of the few 

 fishes exhibiting onshore migration to lower 

 salinities during winter in this area. For many species 



(pollock, Atlantic herring, white hake), migration 



from inshore habitat to offshore is unidirectional for 

 the individual, since each year the beach community 

 consists of the new 0+ year class. For other species 

 (winter flounder, juvenile sculpins, radiated shanny), 

 the return inshore is an annual occurrence, triggered 

 perhaps as much by resource availability and pre- 

 dator avoidance as by physiology. 



Tyler (1971) concluded that in Passamaquoddy 

 Bay movements of large fish independent of the 

 small individuals of a species were not evident for 

 fishes other than hake, but we found obvious dif- 

 ferences in size-class distributions and abundance 

 between summer and winter populations of winter 

 flounder, witch flounder, Atlantic cod, and pollock at 

 offshore sites and a complete lack of most fish 

 inshore. This suggests marked segregation between 

 juveniles (at least 0+ age group) and adults for these 

 species. The use of shallow water habitat as nursery 

 area by fishes of commercial important in the Cana- 

 dian North Atlantic has received little attention. In 

 Europe, this fact has been amply demonstrated for 

 many fish species, including Atlantic cod and pollock 

 (Zijlstra 1972; Daan 1978; Burd 1978; Rauck and 

 Zijlstra 1978). The use of beach habitat as nursery by 

 these fishes makes them susceptible to coastal pollu- 

 tion impacts and puts their adult fisheries at risk to 

 coastal degradation and development, 



Decline in haddock abundance in Passamaquoddy 

 Bay since 1965 coincides with increased numbers of 

 Atlantic cod. However, previous studies indicate lit- 

 tle interaction between these two species (Tyler 1972; 

 Jones 1978). Catches in 1965 (Tyler 1971) coincided 

 with the largest haddock abundance on record 

 (Clark et al. 1981). Fishermen in Passamaquoddy 

 Bay may only catch haddock consistently during 

 years preceded by large recruitment on Georges 

 Bank, the Scotian Shelf, and the Gulf of Maine. 



In the Bay of Fundy region, fish assemblages are 

 segregated according to habitat and, although fish 

 movement is influenced by seasonal climatic regime, 

 assemblages appear cohesive through time. In sum- 

 mer, fishes assembled and exploited the available 

 resources as members of 1) estuarine, 2) beach, 3) 

 offshore, hard-bottom, 4) offshore, soft-bottom, and 

 5) migratory-pelagic assemblages. With winter, 

 movement of species and/or age groups resulted in 

 different seasonal assemblages in each habitat, but 

 major groupings remained essentially intact and 

 replaced each other seaward. The reverse movement 

 occurred in spring. A large portion of benthic and 

 pelagic components occurring at the offshore, hard- 

 bottom habitat were migratory. In contrast, the 

 offshore, soft-bottom assemblage was more senden- 

 tary. Smaller seasonal variation in the water tem- 



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