STUDIES OF THE NIANTIC RIVER, CONNECTICUT WITH SPECIAL REFERENCE TO THE BAY SCALLOP, AEQUIPECTEN IRRADIANS1

The Niantic River is a shallow estuary with a tidal prism equal to half the mcnn low water volume of the basin, and with a twelve-hour freshwater inflow of less than 30~~ of the tidal prism. The tidal waters mix offshore with the waters of castcrn Long Island Sound, rich in plankton and nutrients. The estuary functions as an ecological concentrating system as the dense and varied populations of grazers consuming the food of these tidal waters benefit from the resources of offshore mixing in addition to the production cndcmic to the estuary. The disappcarancc of the eclgrass, Zostera marina, with the epidemic of the early 1930’s permitted bcttcr circulation near the river bottom. Apparently this was advantageous to the bay scallop, which thereafter became the predominant scssile grazer with a production calculated at 2.2g C/mz/yr. Anchorage previously offered by eclgrass for the early setting stages of scallops was subsequently available through the abundance of small branching algae. The brief life history of a bay scallop is outlined on its shell as the surface laid down in each successive year appears rougher or more “weathered” than that formed the year bcforc. By following this diffcrcntiation of shell surface, annual rings were dctermincd with more certainty than in earlier studies. Though the time of year when the differentiation of shell surface commences may vary with populations and even with year classes, it is probably due to a common cause, seasonal change in growth rate being most likely. The life history intcrprcted from shells from Indian middens was essentially the same as observed for living scallops. The scallops of the Niantic River spawn from mid-June through July. The young of a given year reach maturity and are the chief brood stock of the succeeding spawning season. Mortality rates for all sizes are high during all seasons and few individuals survive to the time of second spawning. The estuaries in which the bay scallop occurs have the following hydrographic features: the ratio of tidal volume to river flow is high, thus the salinity remains high; the basin is relatively shallow, with a resulting high ratio of tidal volume to the volume at low water; the circulation is such as to retain the planktonic scallop larvae in sufficient numbers for reseeding and to provide an adequate supply of planktonic food, perhaps in part supplied by offshore waters. INTRODUCTION The field work for this study was supPrior to the 1930’s, the Niantic River in ported by the Waterford-East Lyme EscalConnecticut supported a small little-noticed lop Commission. The courtesies extended to population of the bay scallop, Aequipecten me as a visiting investigator at the Bingham irmdians. In the thirties as the eelgrass, Oceanographic Laboratory, Yale University, &stern, disappeared scallops rapidly inand the field facilities made available at creased in number and gave rise to a sigmy parent’s residence on the Niantic River nificant local fishery which has pcrsistcd to were also vital to the study program. Many this date, Occasional high yields from small individuals and groups helped, a few being parent populations are common for this mentioned where appropriate in the text. species, but continuing high yields after a Support was received from Alfred Universudden increase as observed in the Niantic sity and its Research Foundation. River constitutes an unusual pattern. THE NIANTIC RIVER 1 Contribution No. 26 from the Narragansett The Niantic River (Fig. 1) is an estuary Marine Laboratory. draining into Niantic Bay, a bight at the