Nearshore Community of Fish and Crustaceans

school of menhaden in seine netSince 1980, a long-term study of the community of fish and crustaceans in the nearshore zone of the Rhode River has been one of the major sampling components of the lab. The nearshore zone within the Rhode River is generally shallow, i.e. <1.0 meters deep, with low energy tidal flow. Astronomic tidal amplitude is about 0.5 meters with occasional wind-driven tidal fluctuation up to 2 meters. Annual seining surveys of the nearshore zone are conducted each summer at 13 different sites throughout the Rhode River. By sampling the same areas annually, we can determine spatial and temporal changes in species composition, population size structure, and abundances. Survey sites include the river mouth, small tributaries within the river, shorelines within the river body and the headwaters of the river, bounded by a shallow, saltmarsh creek.

The nearshore area, with its shallow depths and variable habitats, can play a vital role in the survival, nurturing and growth of its juvenile fish and crustacean inhabitants. Our research has shown that small fish, juvenile blue crabs and grass shrimp use the shallow depths 1) as a refuge from larger predators, 2) as nursery grounds for larval fish and small crustaceans and 3) as a resource for food. This research combined with our other longterm sampling programs, which study fish and crustaceans in a tributary creek, epibenthic fish and crustaceans, and the community of infaunal benthic invertebrates. With our 30+ year ongoing data set of estuarine ecological research, we can learn much about the life history of species, including their habitat partionting, their reproduction and recruitment patterns and requirements, their trophic (feeding/energy) levels, and the effect of environmental changes on their behavior. Changes in environmental conditions and their subsequent effects on species may not become evident for several years, and our longterm sampling program helps to clarify often highly variable population trends.

Map of Rhode River Seining Stations

 

seining stations

Sampling is conducted from June 15 until August 31 each year; sequence of station sampling is random from year to year
All species are identified and counted; a subset is measured
13 stations throughout the Rhode River are sampled annually via seine net
7 stations are in sandy bottoms
6 stations are in muddy bottoms
Shoreline composition
2 stations have a sandy beach
2 stations have coarse woody debris
6 stations have emergent vegetation/shrubs
1 station has marshy shoreline
2 stations have a forested shoreline
Seine net
16-meter long minnow seine net with 7 mm mesh
Two replicate (adjacent) seines pulled/station
Each seine samples 33 meters of shoreline pulled from shore to about 10 meters from shore -see photo above.

 

seining at mouth of the river           sorting seine at Muddy Creek

Results to date
50 species of fish and two crustaceans have been identified since the study originated in 1980. Nearly half of these species occur at rare instances and in only one or two stations consistently. The five most abundant species are Fundulus heteroclitus (mummichog), Fundulus majalis (killifish), Anchoa mitchelli (Bay anchovy), Leiostomus xanthurus (spot), and Brevoortia tyrannus (Atlantic menhaden).