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Oceanic or coastal spawning grounds of fish are often distant from nursery areas. Fish larvae require appropriate currents and sufficient and suitable food during transit to reach the nursery area at the proper time, size, and condition. Meteorologic and oceanographic factors influence food availability and transport direction and time. Annual variation in these controlling factors could affect recruitment success. Certain generalizations can be made that apply to marine and estuarine systems. Reproduction occurs in a selected portion of the speciesˈ total range. Spawning often takes place close to gyral, upwelling, or other directional circulations that frequently are associated with major current systems. The coupling of spawning to natural oceanographic transport systems for eggs and larvae is advantageous to a species as long as those systems operate normally. The details of such coupling, and the consequences for eggs and larvae of deviations from usual transport mechanisms, remain poorly understood. Investigation of year‐class success requires a clearer understanding of the natural variability and periodicity inherent in these physical processes. Further research is needed to resolve these details, including environmental cues to reproductive behavior and relative importance of passive and behaviorally mediated transport; to statistically analyze atmospheric and oceanographic cycles; and to quantify transport mechanisms for spawner‐recruit models and predictions of year‐class success.

Physical and biological variables affecting juvenile Pacific herring (Clupea pallasi) in Prince William Sound (PWS) from 1995 to 1998 were investigated as part of a multifaceted study of recruitment, the Sound Ecosystem Assessment (SEA) program. Though more herring larvae were retained in eastern PWS bays, ages‐0 and ‐1 herring used bays throughout PWS as nursery areas. Water transported into PWS from the Gulf of Alaska (GOA) contributed oceanic prey species to neritic habitats. Consequently, variations in local food availability resulted in different diets and growth rates of herring among bays. Summer food availability and possible interspecific competition for food in nursery areas affected the autumn nutritional status and juvenile whole body energy content (WBEC), which differed among bays. The WBEC of age‐0 herring in autumn was related to over‐winter survival. The limited amount of food consumption in winter was not sufficient to meet metabolic needs. The smallest age‐0 fish were most at risk of starvation in winter. Autumn WBEC of herring and winter water temperature were used to model over‐winter mortality of age‐0 herring. Differences in feeding and energetics among nursery areas indicated that habitat quality and age‐0 survival were varied among areas and years. These conditions were measured by temperature, zooplankton abundance, size of juvenile herring, diet energy, energy source (GOA vs. neritic zooplankton), WBEC, and within‐bay competition.

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The diet of juvenile Pacific herring, Clupea pallasi, from four bays in Prince William Sound, Alaska, varied spatially and seasonally. In Zaikof Bay, which was sampled in each season, stomach fullness of this herring was highest in May and declined significantly through the winter. Diversity of prey taxa in the diet was highest in June, after the spring phytoplankton bloom. In October, Oikopleura species were dominant in the fish diets of all bays. In March, fish eggs, Cirripedia nauplii, small Calanoida, and large Calanoida were the dominant prey in Eaglek, Simpson, Whale, and Zaikof bays, respectively. Energy density of stomach contents was highest in May, highlighting the importance of high lipid copepod taxa in Zaikof Bay. Estimated assimilation rates suggest that the diets of smaller age-0 herring provide close to maintenance levels of energy prior to winter. Therefore, variability in diet composition and diet energy density could account for relative differences in nutritional conditions of age-0 herring in Prince William Sound.Résumé : Le régime alimentaire de jeunes Harengs du Pacifique, Clupea pallasi, varie en fonction du lieu et de la saison dans quatre baies du détroit de Prince-William en Alaska. Dans la baie de Zaikof, échantillonnée chaque saison, le remplissage des estomacs de cet Harengs était maximal en mai et diminuait significativement au cours de l'hiver. La diversité des taxons de proies dans le régime était maximale en juin, après l'explosion de phytoplancton du printemps. En octobre, les espèces d'Oikopleura étaient dominantes dans le régime des poissons de toutes les baies. En mars, ce sont les oeufs de poisson qui dominaient dans la baie d'Eaglek, les larves nauplius de cirripèdes dans la baie de Simpson, les petits calanoïdes dans la baie de Whale et les gros calanoïdes dans la baie de Zaikof. La densité énergétique des contenus stomacaux était maximale en mai, ce qui souligne l'importance des copépodes riches en lipides dans la baie de Zaikof. L'estimation des taux d'assimilation indique que le régime alimentaire des harengs d'âge 0 leur a permis d'obtenir presque toute leur densité énergétique de maintien avant l'hiver. La variabilité dans la composition du régime et dans sa densité énergétique peut expliquer les différences relatives des conditions alimentaires chez les harengs d'âge 0 du détroit de Prince-William.[Traduit par la Rédaction] Foy and Norcross 706