Fish and Invertebrates in a Tributary Creek

diagram of Muddy creek fish weir


One of the primary interests of the Fish and Invertebrates Ecology Lab is understanding how fish and invertebrate abundances and community structure change through space and time. To examine the population dynamics and community structure of fish and invertebrates in a small tributary creek, a weir was constructed in 1983. The weir is a series of V-shaped fences that span the mouth of Muddy Creek as it enters the Rhode River. Fish, invertebrates and other organisms are funneled into two openings, one facing upstream and the other facing downstream. At approximately weekly intervals, nets are deployed at the two openings for a period of 24 hours. Therefore, we are able to sample organisms traveling both upstream and downstream over a full tidal cycle. All captured individuals are identified to the species level, enumerated, and a subset is measured. When the nets are not deployed a gate located in the center of the weir is opened to allow fish and crabs to pass freely.

satellite image of Rhode RiverThe Rhode River System (including Muddy Creek) is a small, shallow oligohaline/mesohaline subestuary located approximately 200 km north of the mouth of the Chesapeake Bay in Edgewater, Maryland. This system is primarily characterized by Spartina/Pharagmites-dominated marsh, hardwood forest, adjacent agriculture, private development and fine mud sediments. The Rhode River experiences semi-diurnal tides with an amplitude of approximately 1m. Water temperatures cycle seasonally between 0ºC in January and 30-33ºC in July. Primarily depending on local precipitation salinity can fluctuate.

 

sorting through weir netsSince 1983, 73 species of fish, invertebrates, amphibians, reptiles and mammals have been collected by the weir. Most species occur at relatively low abundances. However, 5 species of fish account for over 92% of the total catch: mummichog (Fundulus heteroclitus), Atlantic menhaden (Brevoortia tyrannus), Atlantic silverside (Menidia menidia), sheepshead minnow (Cyprinodon variegatus), and spot (Leiostomus xanthurus).


 

Other frequently encountered species include, white perch (Morone americana) blue crab (Callinectes sapidus), striped killifish (Fundulus majalis), bay anchovy (Anchoa mitchilli), striped bass (Mornoe saxatilis), pumpkinseed (Lepomis gibbosus), green sunfish (Lepomis cyanellus), common carp (Cyprinus carpio), and gizzard shad (Dorosoma cepedianum).

Other frequently encountered species include, white perch (Morone americana), blue crab (Callinectes sapidus), striped killifish (Fundulus majalis), bay anchovy (Anchoa mitchilli), striped bass (Mornoe saxatilis), pumpkinseed (Lepomis gibbosus), green sunfish (Lepomis cyanellus), common carp (Cyprinus carpio), and gizzard shad (Dorosoma cepedianum).