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Fishery Bulletin 92(1), 1994 



Gilmurray (1980) found mainly microplanktonic 

 prey (e.g., calanoid copepods, cypris larvae, insects) 

 in the diet of alewives less than 80 mm FL obtained 

 from tidal creeks in the upper Bay of Fundy. The 

 shift towards consumption of macrozooplankton 

 likely occurs at fish sizes smaller than those examined 

 in the present study (i.e., <95 mm FL). 



Diel feeding activity during winter and summer, 

 as indicated by the mean fullness index, reached a 

 maximum near mid-day and is typical of size-selec- 

 tive predators which rely on visual cues (Eggers, 

 1977). Summer resident subadult alewives in Minas 

 Basin display a similar feeding pattern, although 

 peak feeding occurred later in the afternoon (1500 

 hours), coincident with the time of high tide when 

 turbidity was lowest and prey visibility highest 

 (Stone, 1985). Summer feeding activity by juvenile 

 anadromous alewives in freshwater also peaks dur- 

 ing the day but ceases or declines overnight ( Jessop, 

 1990). Nocturnal feeding by alewives was more ap- 

 parent during winter than summer; the significance 

 of this seasonal difference in feeding activity is un- 

 clear. Alewives can and do feed efficiently at night 

 using both particulate (Janssen and Brandt, 1978) 



and filter-feeding (Janssen, 

 1978b) modes. 



Alewives greater than 200 

 mm FL generally consumed the 

 largest Meganyctiphanes avail- 

 able. Length-frequency distri- 

 butions of M. norvegica, which 

 has a life span of about two 

 years, are typically bimodal 

 (Hollingshead and Corey, 1974; 

 Berkes, 1976). Alewives selec- 

 tively favor larger prey (Brooks 

 and Dodson, 1965; Brooks, 

 1968; Wells, 1970) and likely 

 use a particulate feeding strat- 

 egy in doing so. Slight seasonal 

 and geographic differences in 

 the average size of M. 

 norvegica ingested likely reflect 

 size differences in euphausiid 

 populations rather than selec- 

 tion by the predator. 



Daily ration calculations 

 were based on the model of El- 

 liott and Persson (1978) which 

 was originally intended for 

 field samples collected within a 

 given area from the same popu- 

 lation over time. Our stomach 

 fullness data for alewives from 

 the Bay of Fundy, Georges 

 Bank, and the Scotian Shelf covered a wide area 

 geographically and may involve more than one popu- 

 lation. The broad temporal and spatial coverage 

 reduces the effect of day-to-day and regional varia- 

 tions in diet which would arise from more restricted 

 sampling. Calculated daily ration levels for alewives 

 off Nova Scotia were similar to those reported for 

 other teleosts (Fange and Grove, 1979). Lower esti- 

 mates were obtained during winter (1.22% BW at 

 7.16°C) than for summer ( 1.88% BW at 7.43°C) since 

 temperature is related to metabolic requirements 

 and to the evacuation rate of stomach contents 

 (Durbin et al., 1983). Both estimates are well above 

 maintenance ration levels for temperatures in the 

 7-8°C range and are sufficient for positive growth 

 (Brett and Groves, 1979). Alewife daily ration de- 

 clined with increasing fish size; small fish, includ- 

 ing marine species such as North Sea cod, Gadus 

 morhua (Daan, 1973), winter flounder, Pseudo- 

 pleuronectes arnericanus (Huebner and Langton, 

 1982) and silver hake, Merluccius bilinnearis 

 (Durbin et al., 1983), generally consume proportion- 

 ally more food per unit weight than large fish 

 (Windell, 1978). Overall, our estimates of daily 



