Research Document - 2001/051
Modelling the Drift of Lobster Larvae off Southwest Nova Scotia
By Drinkwater, K., Hannah, C., Loder, J., Harding, G., and Shore, J.
Abstract
The potential source of the lobster larvae in the Lobster Bay off southwest Nova Scotia is examined by modelling larval drift. Larvae are inserted at a fixed depth into a climatological circulation model from known spawning sites on Georges, Browns and German banks in the offshore of the Gulf of Maine and within Lobster Bay itself. Drift tracks are determined during the summer under varying directional but steady amplitude winds as well as weekly varying winds based on 1988 observations. The model indicates the possibility of particle exchange among many of the offshore (> 50 m isobath) release sites (e.g. Browns, German and Georges Bank) but the probability is low. Few larvae from the offshore banks are found to make it into the inshore zone (< 50 m) of Lobster Bay because of the existence of convergence at the tidal-mixing front over Lurcher Shoals. Based upon our drift model results to date, it would appear that the most likely source of lobster larvae for the inshore area of Lobster Bay is local production. In the deeper midshore region off Lobster Bay, the primary sources of larvae lobster appear to be from German Bank and Browns Bank. Few, if any, of the modelled larvae are transported from Georges Bank towards southwest Nova Scotia. It must be cautioned, however, that these results have not included the effects of vertical migration of the larvae, possibility of directional swimming by the larvae, temperature-dependent larval stage durations, or realistic wind fields.
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