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The Gulf of Alaska is a highly seasonal environment that is characterized by an order-of-magnitude increase in copepod biomass in the photic zone between winter and spring. Copepod recruitment processes, including the location and timing of naupliar production, responsible for the transition from low-biomass winter conditions to the highly productive spring are not well characterized. The recruitment patterns of copepod nauplii were examined in Resurrection Bay, Alaska using biweekly sampling between January and March with zooplankton collected from three depth strata. Nauplii were identified using DNA metabarcoding and species-specific naupliar phenologies were contextualized with environmental data and copepodite and adult copepod population data. This study revealed that nauplii were abundant throughout the winter and were comprised of a diverse assemblage of species. The community composition changed over the course of the season, with different copepod species exhibiting three distinct naupliar phenologies. These include species with nauplii that were 1) present during the winter and absent during the spring, 2) absent during the winter and present during the spring, and 3) present during both winter and spring. Several closely related species were split across groups, revealing temporal niche partitioning of reproduction and naupliar phenologies. For most species in the third group, the presence of nauplii during the winter occurred despite the absence of ovigerous females. While ovigerous females may have been missed or the nauplii could have been sourced from reproductive populations outside of Resurrection Bay, it is also possible that some copepods overwinter as nauplii. Prior to the spring phytoplankton bloom, a moderate increase in chlorophyll α concentrations occurred during March, coinciding with a period of female maturation, an increase in naupliar abundances, and the appearance of later developmental stages. These observations suggest smaller increases in chlorophyll prior to the large spring bloom may be critically important to recruitment of copepod nauplii, their survival, and their growth. 

NOAA’s Alaska Fisheries Science Center’s (AFSC) Ecosystems and Fisheries-Oceanography Coordinated Investigations (EcoFOCI) program has collected spring ichthyoplankton abundance data in the Gulf of Alaska since 1981. Collections were made nearly annually until 2011 when sampling was reduced to only odd years. This dataset is used to better understand population recruitment of major fish species in the GOA and provides early warning of potential year-class strength to inform fisheries management. However, gaps in the time series during even years have made it more difficult to interpret the interannual variability of ichthyoplankton abundance in such a dynamic ecosystem. Recent collaboration with the Northern Gulf of Alaska Long Term Ecological Research (NGA LTER) program has allowed for additional spring sampling of ichthyoplankton in the GOA annually since 2018. Larval fish data collected by the NGA LTER were combined with EcoFOCI data and used to estimate abundance in years when EcoFOCI had no field presence in the GOA. Five taxa were determined to be suitable for this approach based on their percent occurrence in both surveys. A generalized additive model (GAM) was fit to ichthyoplankton data from 1981 to 2022 collected by both EcoFOCI and NGA LTER and used to predict larval abundances in 2018, 2020, and 2022. For each species, models with two different error distributions were compared and shown to produce similar predictions of larval abundance. This report provides a model framework for predicting interannual larval fish abundance while controlling for differences in sampling methodologies, timing, and location, and identifies a subset of taxa for which this framework is currently appropriate. As additional years of concurrent sampling are added in future, this approach has the potential to improve our understanding of interannual variation in ichthyoplankton dynamics and provide more comprehensive indicators for ecosystem-based fisheries management.