Fish community dynamics and nursery habitats in an undeveloped estuary

Estuaries are potentially critically-important fish habitats. However, their temporal and spatial dynamics challenge understanding of the nursery functions of estuaries. Working in the Koeye River estuary in British Columbia, I used size-spectra analysis to infer production and predation risk across the estuary habitat mosaic and track their changes through the season. The brackish mudflat habitat exhibited the highest fish production and lowest inferred predation risk, suggesting that this area had particularly high nursery value. Spectra coefficients were seasonally dynamic, indicating that temporal shifts in the spatial patterns of risks and reward. I also investigated the potential effects of climate change on the distributions of different estuarine fish assemblages by comparing two climatically-divergent sampling seasons. Marine-oriented species expanded their range up-estuary during the dry, more saline year, but freshwater species did not shift. Collectively, this research advances understanding of the spatio-temporal dynamics of estuary nursery functions.