Body size, sex ratio and timing of reproduction of the sand shrimp, Crangon septemspinosa Say (1818), and the distribution of larvae and adults with respect to temperature and salinity, were studied in the estuary of the Kouchibouguac River, New Brunswick. Contrary to predictions, body size was not related to latitude or biogeographic zone. Reproduction in May and June by a cohort of large females, followed in summer and early fall by a cohort of smaller reproductive females, was consistent with previous reports of estuarine populations. Reproduction was continuous throughout the spring and summer, in contrast to the two distinct spawning seasons reported for other northerly populations. Larvae were most abundant in July. At least part of the adult population remained in shallow waters of the estuary throughout the summer, at temperatures up to 28°C, unlike the offshore migrations reported for most other populations during periods of warm water conditions.