Hardened Shorelines Decrease Small Fish and Invertebrate Abundance
New NCCOS-sponsored research shows that shoreline hardening has mostly negative effects on estuarine animals. This is evident both at a local scale directly next to a hardened shoreline and at the larger system-wide scale as the percent of shoreline hardening accumulated in an estuarine area.
Scientists examined 15 common fish and invertebrate species in tributaries of the Chesapeake Bay and Delaware Coastal Bays. The study sites included natural wetlands, beaches, and hardened shorelines in watersheds with different amounts of urban and agricultural land cover. Hardened shorelines generally had lower numbers of small-bodied fishes at the local scale. Larger-bodied species were more numerous directly adjacent to hardened shorelines, but not further offshore, indicating that the positive effect was likely due to the greater water depth associated with the hard shoreline.
Effects on species abundance and community structure were similar for bulkhead and riprap style retaining structures, suggesting that riprap is not necessarily a better choice for habitat than bulkhead. In contrast, natural wetlands supported greater abundance for most species. Notably, abundance was positively related to the percent of estuarine shoreline comprised of wetlands, and negatively related to the percent comprised of hardened shoreline, for two-thirds of the examined species.
These findings provide evidence on the negative cumulative impacts of shoreline hardening. Abundances of several species were also related to watershed cropland cover, submerged aquatic vegetation, and total nitrogen, suggesting that land-use-practices interact with shoreline type to affect prey and refuge habitat.
For more information, contact Beth Turner