During an examination of the distribution of the cladoceran Daphnia in the lakes of southern New England, it was noted that large Daphnia, although present in most of the lakes, could not be found among the plankton of several lakes near the eastern half of the Connecticut coast. The characteristic limnetic calanoid copepods of this region, Epischura nordenskioldi and Diaptomus m1inutus, and the cyclopoid Mesocyclops edax were also absent. Small zooplankters were abundant, especially ithe cladoceran Bosmina longirostris and the copepods Cyclops bicuspidatus thomasi and the small Tropocyclops prasinus (1).All of these lakes lacking large zooplankters have sizable "landlocked" populations of the herring-like Alosa pseudoharengus (Wilson) = Pomolobus pseudoharengus (Fig. 1), known by several common names including "alewife" and "grayback" (2). This is originally an anadromous marine fish, breeding populations of which have become established in various bodies of fresh water, including Lake Cayuga, New York, and the Great Lakes (3).During an examination of the distribution of the cladoceran Daphnia in the lakes of southern New England, it was noted that large Daphnia, although present in most of the lakes, could not be found among the plankton of several lakes near the eastern half of the Connecticut coast. The characteristic limnetic calanoid copepods of this region, Epischura nordenskioldi and Diaptomus m1inutus, and the cyclopoid Mesocyclops edax were also absent. Small zooplankters were abundant, especially ithe cladoceran Bosmina longirostris and the copepods Cyclops bicuspidatus thomasi and the small Tropocyclops prasinus (1).All of these lakes lacking large zooplankters have sizable "landlocked" populations of the herring-like Alosa pseudoharengus (Wilson) = Pomolobus pseudoharengus (Fig. 1), known by several common names including "alewife" and "grayback" (2). This is originally an anadromous marine fish, breeding populations of which have become established in various bodies of fresh water, including Lake Cayuga, New York, and the Great Lakes (3).
The marine populations live in the coastal waters of the western Atlantic, from the Gulf of St. Lawrence to NorthCarolina, and ascend rivers and streams to spawn in springtime. The young return to the sea in summer and autumn (4). The seven Connecticut lakes ( Fig. 2) with self-perpetuating populations of alewives are within about 40 kilometers of the present coastline, and each is drained directly, by a small stream or river, or indirectly, through the estuaries of the larger Connecticut or Thames rivers, into Long Island Sound (Fig. 3). As such streams and rivers are normally ascended by marine alewives, it is assumed that the establishment of these self-sustaining populations in the lakes is natural.The "alewife lakes" are diverse in area and depth. Although we have not examined the food of the alewives in these Connecticut lakes (alewives are difficult to catch), studies in other lakes have revealed that planktonic copepods and Cladocera are the primary food. ...
