Salt Marsh Nekton

members of the salt marsh monitoring crew set up a ditch net used to sample nekton in mosquito ditches
Setting up a ditch net at Fire Island National Seashore. Erika Nicosia / NPS Photo

A Brief Intro

Nekton are free-swimming fishes and crustaceans that are vital signs of salt marsh health, along with tidal wetland elevation and vegetation. Abundant and integral to the ecosystem food web, nekton tell us about primary producers, consumers, top predators, and estuarine change. Water nutrient enrichment, for instance, is a “bottom-up” change that causes harmful algae blooms, which impact nekton nursery grounds. A decrease in nekton populations then affects birds, economically valuable fish, and marine mammals that feed on nekton. Conversely, a “top-down” decline of predatory fish from over-fishing, for example, could mean excessive nekton populations. Both types of change alter the balance, or equilibrium, of salt marsh and estuarine ecosystems.

The Northeast Coastal and Barrier Network monitored nekton from 2009 to 2021. In that time, our data revealed long-term trends in nekton species composition and abundance. With what we learned, we were able to evaluate the dynamic natural and human-induced changes to salt marsh nekton communities.

How We Monitor

  1. Set up sampling locations in the marsh (include areas like marsh pools, creeks, ditches, and shorelines)

  1. Collect samples during low tides, when marsh surface has drained

  1. If sampling location is in a pool, use a throw trap to collect samples. If sampling location is in a ditch, use a ditch net. If both a pool and ditch are present, use the throw trap and ditch net

  2. Repeat sampling once in early summer (June to July) and once in late summer to early fall (August to October). Collect samples from each park every two years

Two researchers sampling nekton in an estuary at Sagamore Hill National Historic Site. John Lee / NPS Photo
Field crew sampling nekton at Sagamore Hill National Historic Site. John Lee / NPS Photo

Where We Monitor

  • Assateague Island National Seashore
  • Cape Cod National Seashore
  • Fire Island National Seashore
  • Gateway National Recreation Area
  • Sagamore Hill National Historic Site


Last updated: December 8, 2021