LARVAL HERRING (CLUPEA-HARENGUS) DISPERSION, GROWTH, AND SURVIVAL IN THE ST-LAWRENCE ESTUARY - MATCH MISMATCH OR MEMBERSHIP VAGRANCY

The relative success of the 1985 spring and fall cohorts of Atlantic herring in the St Lawrence estuary was studied in relation to food availability (match/mismatch hypothesis) and hydrography (member/vagrant hypothesis). Development of the spring cohort (early June) matched remarkably well with development of suitable prey and larval abundance within the estuary decreased slowly (7.8%.d -1). The fall cohort (mid-September) hatched in a period of low food availability and dwindled rapidly (28.9%.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.m -3) and weak in the fall (0.20 J.m-3), suggesting that advection out of the estuary could also have contributed to the observed differences in the fate of the 2 cohorts. Spawning times and locations may have evolved to favor the initial cohesion of larval fish cohorts by limiting dispersion. Both transport and energetic processes can influence the success of a population at colonizing its dispersion area. -from Authors