A QUANTITATIVE SURVEY OF THE INVERTEBRATE BOTTOM FAUNA IN MENEMSHA BIGHT

¹ The Woods Hole Oceanographic Institution, Woods Hole; Washington Square College, New York University, New York

1. A dredge which is larger and heavier than those employed previously in quantitative marine bottom sampling has been used with a specially designed screening device to facilitate the removal of organisms from the relatively large samples of bottom material.

2. The bottom of Menemsha Bight, a flounder fishing grounds in Vineyard Sound, is divisable into five zones on a basis of the bottom material. Four of the zones possessed a distinct faunal aggregation.

3. The zone which extended from the 5- to the 20-meter depth contour and contained a fine sand bottom occupied 80 per cent of the area of the Bight. This zone contained the greatest quantity of the animals (per unit volume of bottom material) that are generally known to serve as food for fishes. Clymenella torquata and Ampelisca macrocephala were the most common organisms. Flounders are caught in greatest numbers in the regions where these animals are most abundant.

4. The numerical distributions of Clymenella torquata and Crepidula fornicata are correlated with distinct characteristics of the bottom.

5. In general, the regions of the Bight containing an abundance of individuals of a common species also contain a large number of different species.

6. The fauna of adjacent stations in a relatively uniform area (Zone 2) may differ considerably in both qualitative and quantitative fashion. This variation is not associated with any observed environmental differences, such as the nature of the bottom material or the depth of water. It may represent the influence of minor factors, or of mechanical aggregation.