Habitat Use by Larval Fishes in Shoreline Waters of the Hudson River

The relative abundance of many fish species is established in the first weeks of life. The larval stage, often called the 'critical period,' experiences mortality typically in the high 90%. Low velocity habitats such as backwaters and near-shore areas are known to support high larval fish densities and serve as nursery habitat for many early life fishes. The upper third of the Hudson River has experienced thousands of hectares of shallow water habitat loss from dredging and filling. While many studies focus on larval distribution in the Hudson River, most of these studies focus on offshore abundances and do not examine shallow water areas. This study aims to correlate larval fish presence to different physiochemical parameters of shallow water microhabitats to inform how further shoreline alteration could affect Hudson River larval fish production. Shallow water habitats in the Tivoli Bay area were point-sampled by 1-m² throw trap collection in the spring of 2010 and 2011. Larval fish were collected, identified, and measured. Microhabitat variables were recorded and analyzed to determine species presence and species abundance within different shallow water microhabitats. First year results suggest considerable heterogeneity and variation in microhabitat definition among families. Clupeids occur in deeper, offshore areas while cyprinids occur in shallow, near-shore, low velocity habitats. Fundulids were present in shallow, silty areas and moronids were found in higher velocity, silty habitat. Furthermore, we observed a positive correlation between minimum fish size and water velocity for several species, suggesting that larvae are habitat-limited by velocity. Efforts aimed towards expanding shallow water habitat for larval fishes should consider taxa-specific habitat restructuring. Similarly, altering existing shallow water habitats may disproportionately impact reproductive potential of the fish fauna depending on magnitude and type of habitat shift.