A study of the arkshell clams, Noetia ponderosa (Say 1822) and Anadara ovalis (Bruguiere 1789), in the oceanside lagoons and tidal creeks of Virginia

Two species of arkshell ("blood'') clams, Noetia ponderosa and Anadara oval is, have recently been targeted by watermen on the eastern shore of Virgini a for sale to both East and West Coast markets in the United States. Until 1991, fishermen caught both species in the harvest of oysters and hard clam s, and discarded them as bycatch with little value. Very little is known ab out either species of blood clam, and preliminary data from a pilot study i n 1993 indicated that they were being over-fished. We conducted a survey in September 1994 in the oceanside lagoon system along the eastern shore of A ccomac and Northampton Counties, Virginia, and collected data on density, a bundance, habitat preference, age-size and morphometric relationships, and mortality rates for both species of blood clams, as well as some ancillary data on the hard clam, Mercenaria mercenaria. The study provides baseline d ata for establishing management practices and regulations for the blood cla m fishery. The total estimated abundance in the study area was about 16 mil lion N. ponderosa and 6.4 million A. ovalis. Of the clams taken in commerci al catches on the oceanside of the eastern shore, M. mercenaria constitutes about 84%, N. ponderosa 15%, and A. ovalis 1%. In our field survey, M. mer cenaria was the most abundant species (72% of the total catch), followed by N. ponderosa (17%) and A. ovalis (11%). Densities for blood clams averaged 0.35 clams m(-2), or 3,500 clams per hectare, and were highest in shell an d shell/mud substrate (1.1 and 1.2 clams m(-2), respectively). Growth studi es and age-size data show that A. ovalis grows about twice as fast as N. po nderosa and that market-size IV. ponderosa (about 56 nim in shell height) m ay be 8+ years old. We also present information on mortality rates and morp hometric relationships for both species of blood clams, and recommendations for maintaining and enhancing the fishery.