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.

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Two field surveys were conducted in Newfoundland, Canada: (1) SCUBA surveys at four sites differing in bottom type and the presence/absence of vegetation and (2) beach seining at three sites containing eelgrass (Zostera marina) and no-eelgrass locations. Results indicated that eelgrass is used as a nearshore habitat by age 0 + Atlantic cod (Gadus morhua). A subsequent laboratory experiment compared the use of patches of bottom substrates (sand, gravel, cobble) and artificial eelgrass (three densities) by age 0 + cod when in the absence and presence of a predator (an age 3 + conspecific). Before exposure to a predator, age 0 + cod associated with sand and gravel. With a predator present, in substrate combinations with cobble, age 0 + cod hid in the interstitial spaces of this substrate or in the patch of eelgrass when stem density was >=>720 stems/m2. In combinations with no cobble, age 0 + cod hid in the eelgrass regardless of stem density. Latency to capture an age 0 + cod was highest and the total number of age 0 + cod captured lowest in combinations with cobble or the patch of vegetation with 1000 stems/m2. In the remaining combinations, latency until an age 0 + cod was captured increased with both the presence and density of vegetation.

We use a simple model of temperature‐dependent egg development and mortality to develop several hypotheses concerning the effect of temperature on the occurrence of eggs of Atlantic cod, Gadus morhua, in Placentia Bay, Newfoundland. Predictions from this exploratory model were tested through a series of synoptic ichthyoplankton surveys throughout spawning and postspawning periods during 1997 and 1998. Although several egg mortality relationships were explored through the simulation, a constant mortality rate best represented the pattern observed in the two years of data. Peaks in late stage egg densities occurred in August of both 1997 and 1998 and were apparently decoupled from egg production peaks in April. We observed a decrease in mortality and the distance dispersed during egg development with increases in water temperature. We suggest that the effects of predation are small relative to the advective effects within this system, and that the interaction between advection and temperature‐dependent vital rates of eggs may have dramatic consequences for coastal retention of propagules produced by inshore spawning events.