Nekton (defined as free swimming fishes and crustaceans) are an abundant estuarine fauna that provide an integral link between primary producers, consumers, and top predators. They are likely to respond to either top-down or bottom-up estuarine perturbations. For example, nutrient enrichment (a bottom–up perturbation) could affect nekton by altering submersed vegetative habitats that serve as nursery grounds. Conversely, removal of predatory fishes through over-fishing (top-down) could induce responses in the forage or prey nekton. Nekton also represent a significant portion of the diets of many fish-eating birds, economically valuable fishes, and (in estuaries) marine mammals.
Monitoring nekton over time will help evaluate both natural and human-induced changes in estuarine nekton over the long-term and will advance our understanding of the interactions between nekton and the dynamic salt marsh and estuarine environment.
Determine long term trends in species composition, abundance and size structure in nekton communities in selected NCBN park salt marshes.
At each study marsh, 15 to 25 sampling locations will be established where nekton will be collected, depending on the available habitat. Sampling locations may include marsh pools, creeks, ditches and shoreline areas, depending on the topography of the site. Depending on the amount and type of open water habitat (pools or ditches) on the marsh, two different sampling techniques (throw trap and ditch net) will be employed. If pools and ditches are both present within the marsh, both habitats will be sampled. Pools and ditches will be sampled on ebbing tides, when the marsh surface has drained. Sampling will occur twice per year, once in early summer (June-July) and once in late summer-early fall (August – October).