Interannual variations in larval fish recruitment to estuarine epibenthic habitats

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Abstract
The presence of early life stages of more than 45 fish species in epibenthic sled collections from North Inlet Estuary, South Carolina (USA) indicated that subtidal creek bottoms are important nursery habitats. Biweekly collections from 1981 to 1985 revealed 2 distinct periods of larval fish recruitment: summer, in which gobies Gobiosoma spp. and anchovies Anchoa spp. dominated; and winter, in which spot Leiostomus xanthurus and Atlantic croaker Micropogonias undulatus dominated. For every major taxon, date of arrival, duration of the recruitment period, and size distribution were similar among years. Arrival of early stage larvae was continuous within each annual period, but patterns of abundance were not consistent from year to year. Large and irregular fluctuations in abundance between sampling dates accounted for the largest sources of variation in nested ANOVAs conducted for each of 8 major taxa, but these fluctuations were not explained by short-term changes in water temperature or salinity. However, during the extended period of low salinity in the winters of 1983 and 1984, winter taxa were significantly more abundant than in other years. Low salinity conditions represented extreme changes for an otherwise high salinity estuary, yet no notable differences in the taxonomic composition, ranks, or timing of arrivals were observed between the 4 winters sampled. Collections were made at sites representing the 2 dominant subtidal habitat types, and even though densities were consistently higher at an upestuary creek lacation than at one near the inlet, seasonal and annual patterns of abundance were very similar. Further, size distributions of larval fishes were very similar at both locations. These observations suggest that factors controlling larval fish recruitment and fluctuations in abundance were operating on a large spatial scale. Major ecosystem level distrubances such as extreme reductions in salinities during some winters did not appear to alter temporal patterns of larval fish recruitment as much as the magnitude of utilization of epibenthic habitats.