Larval Herring (Clupea harengus) Dispersion, Growth, and Survival in the St, Lawrence Estuary: Match/Mismatch or Membership/Vagrancy?

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Abstract
The relative success of the 1985 spring and fall cohorts of Atlantic herring (Clupea harengus) in the St. Lawrence estuary was studied in relation to food availability (match/mismatch hypothesis) and hydrography (member/vagrant hypothesis). The development of the spring cohort (early June) matched remarkably well the development of suitable prey and larval abundance within the estuary decreased slowly (7.8% .cntdot. d-1). The fall cohort (mid-September) hatched in a period of low food availability and dwindled rapidly (28.9% .cntdot. d-1). The initial growth of both cohorts appeared limited by food. The stratification front limiting seaward drift was strong in the spring (0-80 J .cntdot. m-3) and weak in the fall (0-20 J .cntdot. m-3), suggesting that advection out of the estuary could also have contributed to the observed differences in the fate of the two cohorts. We conclude from this case study that spawning times and locations may have evolved to favor the initial cohesion of larval fish cohorts by limiting dispersion and that both transport and energetic processes can influence the success of a population at colonizing its dispersion area. The relative contribution of initial vagrancy and subsequent trophic interactions in determining final recruitment remains to be assessed.