Intertidal Creek Pool Nekton Assemblages: Long-term Patterns in Diversity and Abundance in a Warm-Temperate Estuary

Estuarine nekton (fishes, crabs, and shrimps) play key ecological roles and support valuable commercial and recreational fisheries. Long-term research programs focused on nekton can provide insight into community and population-level changes over time, but are uncommon due to funding and logistical constraints. We describe patterns and changes in a nekton assemblage from an intertidal creek in the North Inlet estuary, South Carolina, USA based on 19 years of observations. From 1984 to 2002, biweekly seine collections (approximately every 2 weeks, n = 469) were made in a pool isolated within an intertidal creek at low tide. The assemblage was composed of juvenile and small adult (mostly < 100 mm) fishes, shrimps, and crabs. The 10 most abundant species made up > 97% of the catch; these species included (in descending order): Leiostomus xanthurus , Litopenaeus setiferus , Fundulus heteroclitus , Mugil cephalus , Farfantepenaeus aztecus , Eucinostomus spp., Mugil curema , Fundulus majalis , Menidia menidia , and Brevoortia tyrannus . The assemblage exhibited a distinct seasonality across years, with peak total abundance in mid-spring, peak total biomass in late spring, and highest species richness in late summer and early fall. Total abundance and species richness showed evidence of significant increases across years, total biomass and the Shannon diversity index remained unchanged, and evenness significantly declined. The composition of the assemblage shifted during the sampling period, with the abundance of key year-round residents ( F. heteroclitus , M. cephalus ) decreasing and warm-season species ( L. xanthurus ) increasing. Most of the five metrics of the nekton assemblage and the abundances of the five top species were positively correlated with both water temperature and salinity. Direct and indirect effects of hurricanes and storm events on the hydrogeomorphology of the creek and pool were also recognized as influences on the long-term patterns and trends. Long-term (decadal) sampling programs like this can provide important baseline information, and thus insight into the influence of significant weather events and global climate change on nekton populations and their roles in ecosystem dynamics, as well as inform the management of estuaries and fisheries in the southeastern US.