Transport and development of eggs and larvae of Atlantic cod, Gadus morhua, in relation to spawning time and location in coastal Newfoundland

Abstract

We provide evidence that variation in location and timing of spawning of Atlantic cod, Gadus morhua, has a major impact on occurrence, distribution, and development of eggs and larvae in a large embayment on the south coast of Newfoundland. Atlantic cod egg densities, measured with a series of ichthyoplankton surveys in Placentia Bay during the spawning and postspawning seasons of 1997 and 1998, were highest during the early spring of both years and decreased through the spring and summer. Egg development stages and larval size suggest that eggs and larvae were released from spawning locations within the bay and developed as they were transported in cyclonic flow from the southeast and around the bay towards the southwest, where late-stage eggs and larvae were found to be most abundant. Although egg densities were generally lower in 1998, late-season egg production during the summer of 1998 was elevated in relation to 1997, providing a possible explanation for the observation that larval total densities were more than an order of magnitude higher in 1998 than in 1997. In terms of larval production, late spawners may be particularly important to successful egg hatching in the coastal waters of Newfoundland.