168 



Fishery Bulletin 92(1], 1994 



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Time (h) 



Figure 7 



Diel feeding chronology of alewives, Alosa 

 pseudoharengus , from winter and summer 

 groundfish research surveys off Nova Scotia 

 (1990-91), as determined from changes in 

 fullness index values. Data are means (arc- 

 sine \'p transformed with 95% confidence in- 

 tervals) placed at the midpoint of each 3-hour 

 (winter) and 4— hour (summer) interval. Aster- 

 isk denotes mean significantly different (P<0.05) 

 from that of previous time interval. Sample size 

 is adjacent to each symbol. Open and solid por- 

 s of horizontal bars represent light and dark 

 hours during winter and summer. 



ration may be on the low side because of possible 

 weight loss in M. norvegica due to the effects of for- 

 malin preservation (Steedman, 1976). However, 

 weight loss in euphausiids preserved for up to one 

 year would likely be less than 10% because of their 

 large size and low lipid content (Sameoto, 1993 1 ). 



1 D. Sameoto, Bedford Institute of Oceanography, Dartmouth, 

 Nova Scotia B2Y 4A2, pers. commun. July 1993. 



The higher mean stomach fullness indices during 

 summer in the Bay of Fundy and winter on the 

 Scotian Shelf indicate that these regions are season- 

 ally important foraging areas for alewives. Off Nova 

 Scotia, alewives fed most actively (judged by the 

 proportion of feeding fish and their stomach full- 

 ness) where oceanic conditions, particularly depth 

 (>200 m) and temperature, were suitable for M. 

 norvegica (Kulka et al., 1982; Sameoto et al., 1993). 

 Alewives prefer bottom temperatures of 7— 11°C off- 

 shore at mid-depths in spring ( 101-183 m), in shal- 

 lower nearshore waters in summer (46-82 m) and 

 in deeper offshore waters in fall ( 119-192 m) (Stone 

 and Jessop, 1992). During winter, Meganyctiphanes 

 seeks deeper, warmer water rather than the cold 

 upper layers (Bigelow, 1926; Hollingshead and 

 Corey, 1974). While the seasonal pattern of move- 

 ment by alewives (inshore and northward during 

 spring and offshore and southward during fall) is 

 partially linked with spawning migrations, it is 

 apparent that their marine distribution is also in- 

 fluenced by the distribution, availability, and abun- 

 dance of their main prey, M. norvegica. 



Acknowledgments 



We thank D. Sameoto and R. Cutting for critically 

 reviewing earlier drafts of the manuscript. We also 

 wish to thank M. Strong, P. Fanning, and J. Martell 

 for collecting the alewives used in our analyses, S. 

 Wilson and J. Tremblay for taxonomic assistance, 

 and D. Ingraham for helping with laboratory work. 



Literature cited 



Ackman, R. G., C. A. Eaton, J. C. Sipos, S. N. 

 Hooper, and J. D. Castell. 



1970. Lipids and fatty acids of two species of North 



Atlantic krill (Meganyctiphanes norvegica and 



Thysanoessa inermis) and their role in the aquatic 



food web. J. Fish. Res. Board Can. 27:513-533. 



Berkes, F. 



1976. Ecology of euphausiids in the Gulf of St. 

 Lawrence. J. Fish. Res. Board Can. 33:1894- 

 1905. 

 Bigelow, H. G. 



1926. Plankton of the offshore waters of the Gulf 

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 Bigelow, H. B., and W. C. Schroeder. 



1953. Fishes of the Gulf of Maine. Bull. U.S. Fish 

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 Bowman, R. E. 



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