Benthic survey for populations of soft-shelled clams,Mya arenaria, in the lower Potomac River, Maryland
Tóm tắt
Exploratory sampling of the potential soft-shelled clam bottoms in the Potomac estuary was conducted to define the range and densities of the subtidal populations ofMya arenaria. Bottom samples were taken at depths ranging from 3 to 11 feet with the Maryland hydraulic clam dredge using a 3/8-inch mesh conveyor belt. Clam populations ranged from the mouth of the river to Popes Creek, approximately 40 miles upriver. The more dense populations of over 300 bushels per acre were found between Sandy Point and Swan Point, or 16 to 33 miles from the river mouth. Clam densities were extremely variable in this area, and were related to changes in bottom type and the instability of shoal water bottoms brought about by wind and wave action. Sixteen other benthic macro-invertebrates which were collected in 189 bottom samples are reported along with their relative densities and distribution in the river. The pelecypodsMacoma balthica andM. phenax were the most abundant and widely distributed invertebrates collected by the dredge throughout the sampled area. The number of species declined with the decreasing upriver salinity gradient, indicating the essentially marine elements in the benthic fauna.
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