Factoring scales of spatial and temporal variation in fish abundance in a subtropical estuary

Abstract

We employed a new approach linking multivariate and time series analyses to iden- tify common versus unique spatiotemporal components of abundance variation of marine spawn- ing fishes recruiting into a subtropical Western Atlantic estuary. Based on a 10 yr standardized monthly data set, we also investigated patterns of association for local and regional factors with annual and inter-annual variation in abundance of 5 dominant marine estuarine-dependent fishes. The total amount of variation in fish abundance explained by environmental variables was 22.4%. After factoring out shared spatiotemporal variation (0.8%), our analysis showed that tem- poral components had an almost 5-fold greater contribution (28.0%) than spatial components (6.4%) in explaining the variation in abundance of the 5 species. Most of the variation across the temporal scale (58.5%) was associated with annual (from 0.5 to 1.3 yr) rather than multi-year oscil- lations (>2 yr). Such annual patterns were probably associated with adaptations of marine estuar- ine-dependent fishes for exploiting predictable pulses in seasonal productivity typically found in subtropical estuaries. In contrast, inter-annual variation in abundance occurring at a scale of 3 to 7 yr could be attributed to rainfall anomalies associated with El Nino Southern Oscillation (ENSO) events, whereas those occurring at a scale of 2 yr could be influenced by the Southern Annular Mode (SAM). Our findings corroborate the hypothesis that prevalent annual patterns of variation in the abundance of marine estuarine-dependent fishes are associated with predictable productiv- ity pulses linked to the annual temperature regime, whereas inter-annual variations in fish abun- dance are associated with the influence of large-scale climatic phenomena.