A f~e l d study was conducted on clams Macoma b a l t h~c a (L ) in 6 adjacent bays along the south shore of the Lower St Lawrence Estuary Data collected at 12 stations from the upper and lower levels of the tidal zone showed that the length-specific energy budgets of shell somatic tissue and sexual products were very vanable between stations d u r~n g the 1986 g r o w n g season In each bay the standard length-specif~c (5. 10 and 15 mm) energy budget values were greater at the lower level

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... ons than at the upper level stations except in one bay where the reverse was true Tldal level effects on ind~vldual growth were tar stronger than both density and s e d~m e n t effects Intra-populat~on vanatlons in shell, s o m a t~c t~s s u e and gamete product~on d u e to the tidal level effect were more important than the ~nter-bay vanations due to local density and/or s e d~m e n t effects The s~g n~f i c a n t relat~onships between hdal level and length-specif~c energy budget of each body component allowed us to construct a 3-dimens~onal model s h o w~n g the seasonal length-specific product~on In shell, flesh and sexual products at each tidal level ot a t~d a l flat From these models, it appears that In each bay the seasonal (May to November) production In shell, somatlc tlssue and sexual products was mostly attributable to a small number of ind~viduals l i v~n g in the lower part of the t~d a l flat