Fish Species Distribution in Seagrass Habitats of Chesapeake Bay are Structured by Abiotic and Biotic Factors

Seagrass habitats have long been known to serve as nursery habitats for juvenile fish by providing refuges from predation and areas of high forage abundance. However, comparatively less is known about other factors structuring fish communities that make extensive use of seagrass as nursery habitat. We examined both physical and biological factors that may structure the juvenile seagrass-associated fish communities across a synoptic-scale multiyear study in lower Chesapeake Bay. Across 3years of sampling, we collected 21,153 fish from 31 species. Silver Perch Bairdiella chrysoura made up over 86% of all individuals collected. Nine additional species made up at least 1% of the fish community in the bay but were at very different abundances than historical estimates of the fish community from the early 1980s. Eight species, including Silver Perch, showed a relationship with measured gradients of temperature or salinity and Spot Leiostomus xanthurus showed a negative relationship with the presence of macroalgae. Climate change, particularly increased precipitation and runoff from frequent and intense events, has the potential to alter fish-habitat relationships in seagrass beds and other habitats and may have already altered the fish community composition. Comparisons of fish species to historical data from the 1970s, our data, and recent contemporary data in the late 2000s suggests this has occurred

Hydrodynamics of vegetated channels

This paper highlights some recent trends in vegetation hydrodynamics, focusing on conditions within channels and spanning spatial scales from individual blades, to canopies or vegetation patches, to the channel reach. At the blade scale, the boundary layer formed on the plant surface plays a role in controlling nutrient uptake. Flow resistance and light availability are also influenced by the reconfiguration of flexible blades. At the canopy scale, there are two flow regimes. For sparse canopies, the flow resembles a rough boundary layer. For dense canopies, the flow resembles a mixing layer. At the reach scale, flow resistance is more closely connected to the patch-scale vegetation distribution, described by the blockage factor, than to the geometry of individual plants. The impact of vegetation distribution on sediment movement is discussed, with attention being paid to methods for estimating bed stress within regions of vegetation. The key research challenges of the hydrodynamics of vegetated channels are highlighted.National Science Foundation (U.S.) (Grant No. EAR0309188)National Science Foundation (U.S.) (EAR0125056)National Science Foundation (U.S.) (EAR0738352)National Science Foundation (U.S.) (OCE0751358

Implementation Plan for Removing Impediments to Migratory Fishes in the Chesapeake Bay Watershed

As part of its effort to implement the \u27Strategy for Removing Impediments to Migratory Fishes in the Chesapeake Bay Watershed,\u27 the Fish Passage Workgroup of the Living Resources Subcommittee has developed the attached Implementation Plan. The Plan is presented in tabular form based on the Strategy Recommendations. It identifies the necessary implementing actions, responsible agencies, and the schedule for completing the listed actions. The Plan also includes an estimate of recources needed through the 1992 Budget Year. Section II of the document contains Progress Reports for the respective jurisdictions indicating the activities undertaken in 1989