Secondary production of benthic molluscs from the delaware bay and coastal area

Abstract

Secondary production of benthic molluscs was estimated for one Delaware Bay site and two coastal Delaware sites for 1980 and 1981. Direct measurements of production ( P = mg AFDW m −2 year −1), mean biomass ( B = mg AFDW m −2 ) and turnover ratios ( P: B ) for six select species ranked as follows: Ensis directus ( P = 6·1–8674·0, B = 1·2–1230·4 , P: B = 5·0–14·1 ); Mytilus edulis ( P = 0·2–13384·2, B = 0·2–2169·5 , P: B = 1·0–6·2 ); Nucula annulata ( P = 16·7–844·0, B = 10·3–604·8 , P: B = 0·4–6·2 ; Nucula proxima ( P = 1·7-1·9, B = 0·3-0·4 , P: B = 1·8-5·7 ); Spisula solidissima ( P = 0·6–873·9, B = 0·4–194·4 , P: B = 1·5-5·7 ); and Tellina agilis ( P = 136·1–7648·0, B = 19·4–2782·4 , P: B = 2·1–7·0 ). Indirect measurements of remaining mollusc species accounted for a range of 26·2–59·0% of total mollusc production. Total mollusc production was highest at the Delaware Bay station (21775·0 mg AFDW m −2 year −1), slightly lower at the coastal station nearest the Bay mouth (19206·3 mg AFDW m −2 year −1) and markedly lower at the coastal station furthest from the Bay mouth (1571·0 mg AFDW m −2 year −1). This pattern also reflected an association with sediment type as production was higher in fine sand than in coarse sand. Peak production varied seasonally and there was considerable annual variability at two stations. It was concluded that estimates of secondary production and turnover ratios of dominant Delaware Bay area molluscs were similar to estimates for the same species or related species from other similar habitats.