NOTES Ojeda and Dearborn: Populations of fishes and crustaceans in the Gulf of Maine 405 



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Figure 1 



(A) Surface water temperature in 

 Pemaquid Point, Maine, during 

 1985-86. (B) Temporal variation 

 in the number of species (dashed 

 line) and relative abundance (solid 

 line) of fish captured with experi- 

 mental gillnets at Pemaquid Point, 

 Maine, during 1985-86. Abun- 

 dances are expressed as captures 

 per unit effort (CPUE). 



The most abundant species were juvenile pollock and 

 cunners (Table 1). Most of these pollock were immature 

 individuals averaging 215 mm TL, which correspond 

 to pollock of about 1 year-old (Bigelow and Schroeder 

 1953). Six other species were relatively common (rep- 

 resented by more than 2% and less than 10% of the 

 total number of specimens collected: spiny dogfish, 

 cod, mackerel, and sculpins). Most of the cod captured 

 were juveniles averaging 300 mm TL, which corre- 

 spond to an age of ~2 years (Bigelow and Schroeder 

 1953). Each of the remaining 13 species (61.9% of the 

 total number of species) were represented by less than 

 2% of the total number of fish captured (Table 1). 



Captures of all three sculpin species, pollock, and cod 

 were significantly greater during the night than dur- 

 ing the day (x~ test for goodness of fit, P<0.05) sug- 

 gesting that these fish are primarily crepuscular and/or 

 nocturnal predators. 



On the other hand, cunners, mackerel, and spiny 

 dogfish were captured almost equally during the day 

 and at night (P>0.05). In contrast to mackerel and 

 spiny dogfish, cunners were very rarely observed to 

 be active at night, indicating they are primarily diur- 



nal predators in these environments, as previously 

 shown by Chao (1973), 011a et al. (1975), and Dew 

 (1976). 



Temporal patterns 



Surface-water temperature of the littoral zone followed 

 a seasonal cycle typical of cold waters of the Gulf of 

 Maine (Fig. 1 A), as shown by Tyler (1971) and MacDon- 

 ald et al. (1984). Maximum values of about 18°C were 

 observed during summer (July-September), and 

 minima of about 1-2°C occurred during winter (Feb- 

 ruary-March). Both the abundance and diversity of fish 

 showed a clear seasonal pattern closely paralleling the 

 seasonal variation of water temperature (Fig. IB). Fish 

 abundance peaked during summer, reaching values of 

 30-34 fish/hour, and was lowest (near zero) during 

 winter. Species diversity followed a similar seasonal 

 pattern (Fig. IB). These results suggest a seasonal 

 migration (inshore-offshore) of most components of 

 this fish assemblage, which appears to be correlated 

 with temperature changes. 



