Utility of storage lipid volumes in inferring recent trophic history of copepods

We were able to estimate lipid oil-sac volumes of Pseudocalanus spp. copepo dids c3 to c5 on and around Western Bank, Scotian Shelf, during three cruis es (October and November 1997 and January 1998) at stations on (< 60 m dept h) and off (> 60 m depth) the bank. We test the hypothesis that storage lip id volume was not significantly different between locations during these th ree months. Pseudocalanus spp. are an important prey for Atlantic cod (Gadu s morhua) larvae that are spawned and persist on the bank. However, in cont rast with the greater concentration of Pseudocalanus spp. on relative to of f the bank, size-adjusted oil-sac volumes were on average larger and less v ariable at off-bank stations. We conclude that the greater copepod concentr ation on the bank does not result from enhanced and uniform nutrition on th e bank. Lipid volumes averaged larger in winter than in the autumn, indicat ing that nutritional condition of Pseudocalanus spp. copepodids does not de cline subsequent to the autumn bloom. Although biochemical techniques are a vailable to quantify the level of storage lipids in individual copepods, si mple measurements of oil sacs and body sizes permit a rapid real-time asses sment of their recent trophic history in relation to oceanographic structur e.