Spatial surface temperature correlates of American lobster (Homarus americanus) settlement in the Gulf of Maine and southern New England shelf

Abstract

American lobster, Homarus americanus H. Milne-Edwards, 1837, populations along the east coast of North America are geographically distributed over some of the steepest latitudinal ocean temperature gradients in the world. A disconnect between spawner biomass and postlarval settlement, i.e., young-of-year (YoY) recruitment, to the sea bed at the end of the larval season highlights the role of external environmental factors. To understand the spatial dimension of sea surface temperature correlates of settlement, we compared over two decades of inter-annual variation in lobster settlement at three oceanographically contrasting areas: the Bay of Fundy, coastal Gulf of Maine, and southern New England, with satellite-derived sea surface temperature anomaly (SSTa) patterns over the coastal regions and shelf waters. Correlations were performed between the settlement time series and monthly SSTa maps at time lags relevant to larval hatching, development, transport, and settlement. Settlement was significantly and positively correlated with SSTa in southern New England, showing associations with upstream areas over Georges Bank and southern Nova Scotia during months when larvae are expected in the water column (July–August). The Gulf of Maine site was correlated with SSTa in the immediate vicinity of the settlement site, and only in the month of settlement sampling. Settlement at the Bay of Fundy site was not correlated to SSTa patterns. The observed associations are consistent with larval advection by residual oceanic flow structure in the region, and are further supported by studies on lobster larval supply and genetic connectivity reported in the literature.