Life-history patterns of Haustorius canadensis (Crustacea: Amphipoda) in northern New England

The population of Haustorius canadensis at Long Sands Beach in southern Maine was sampled monthly over a period of 45 months. The population showed seasonal movements upshore during spring and downshore during the autumn and winter. In southern Maine, H. canadensis has a mixed annual–biennial life history, with approximately one-half of the population reproducing after 1 year and the remainder reproducing during the second year. This pattern contrasts with the annual life history observed on the southern shore of Cape Cod. This shift in life history is discussed in terms of a gradient of habitat temperatures. The minimum size of a reproductive female was approximately 6 mm. Males were smaller than females. The sex ratio remains close to 1:1 throughout the year