The Shellfish Resource in a Polluted Tidal Inlet

Extract

In the City of Gloucester, Massachusetts, 30% of the Soft-shell Clam (Mya arenaria) beds in a tidal inlet known as the Annisquam River are not harvestable owing to the discharges of untreated sewage from the surrounding area. A large proportion of the total area of the clam-flats has been closed to clamming because of exceedingly high levels of coliform Bacteria in the clams and in the water. These polluted areas represent a ‘loss’ of resources for the community, and they were surveyed in 1980 to determine the number and value of Clams which could have been harvested if only the sewage discharges had been controlled.

In the productive areas of the closed-to-fishing flats, which totaled 25.9 ha, the densities of Clams larger than 2.5 mm were found to be statistically the same on the 9 flats sampled and averaged 122.3 per m². The average number of legally harvestable Clams (those with shells more than 51 mm in length) was 23.3 per m², and the total yield that could have been harvested in 1980 was estimated at 6 × 10⁶ Clams. Assuming that only 50–60% of the Clams would actually have been harvested in a year (i.e. 3.2 × 10⁶ animals), the local community lost $332,400 in retail sales alone for lack of adequate sewage treatment facilities. Locally, 70% of the harvest goes into the restaurant trade where a bushel (35.2 1), which contains some 1,600 animals, retails for $210, and 30% is sold fresh at $64 per bushel.