FACTORS INFLUENCING THE SPATIOTEMPORAL OCCURRENCE OF FISH EGGS AND LARVAE IN A NORTHERN, PHYSICALLY DYNAMIC COASTAL ENVIRONMENT

Distribution patterns, abundance and species composition of the assemblages of fish eggs and larvae in Conception Bay, Newfoundland, Canada, during the early summers of 1990 and 1991 are described. Several species appear to use Conception Bay as a spawning ground. Interannual and seasonal differences in both species composition and abundance in the bay appear to be associated with differences in environmental conditions, particularly with temperature. Both egg and larval abundances were lower by an order of magnitude in 1991 corresponding to the coldest and less saline waters. Temperature and wind were the environmental factors most associated with the spatial distribution of eggs. In both years, highest abundances of all species were usually found at the head and the eastern side of the bay, corresponding to the warmest waters under dominant westerly winds. On one occasion, greatest abundances and warmer waters were found on the western side of the bay, concomitant with a southerly wind episode. Clustering samples by their relative species composition revealed well-defined assemblages of fish larvae. The variability in relative species composition was strongly associated with the physico-chemical conditions of the surface layer and was consistent with patterns of seasonal successions observed in other ecosystems. We propose that temperature is the principal factor controlling spatio-temporal occurrence of fish eggs and larvae in Conception Bay and, most probably, in coastal waters of Newfoundland and Labrador, Canada. This association may be critical in ecosystems characterized by an extremely short growing season. Conception Bay may play an important role in the early-life history of fish inhabiting the northeast Newfoundland/Labrador shelf. Even if a smaller proportion of fish reproduced in the coastal region, their offspring may contribute significantly to the number of individuals recruiting to the population if growth and survival are considerably higher in coastal areas than in offshore areas due to the presence of more favourable habitats for early-life stages of fish.