Seasonal succession of the larval fish community from coastal areas of eastern Newfoundland, Canada

We present a synthesis of all sampling programs aimed at collection of ichthyoplankton conducted in coastal waters of eastern Newfoundland during the period 1982–2016, describing seasonal patterns in the succession of 22 taxa in terms of diversity, probability of occurrence, and overall abundance. Additionally, we assess whether changes in these patterns occurred prior to and after the collapse of major commercial fish stocks and accompanying shifts in ecosystem structure. Despite differences in relative species composition and community structure among bays, we identified clear and repeatable patterns in the seasonal cycle of species succession from Placentia Bay, on the south coast, to White Bay on the northeastern coast of the island. Some of the differences among bays reflected latitudinal patterns in the timing of the seasonal environmental cycle, with increasing delays toward northerly bays. Relatively few species generally dominated the larval fish community, although dominance varied seasonally, particularly once emergence of capelin commenced in July and August. Abundance of larval fish reflected the changes in abundance of adult stocks of commercial species, with strong declines in density following stock collapses, but larval decreases extended to non-commercial coastal taxa potentially removed as bycatch or through impacts of changes in ocean conditions that contributed to the decline of major ecosystem stocks (e.g., Atlantic cod, capelin, American plaice). Although differences in timing and extent of ichthyoplankton collections confounded our data, the general consistency of our observations with other sources of information (e.g., research vessel trawl surveys) highlights the value of such collections to monitoring of areas poorly represented by other types of surveys. Knowledge of changes in larval fish community structure in coastal areas can set a foundation to understand better the potential interaction between anthropogenic and climate impacts on the ecosystem state in coastal areas.