Spatial differences in the productivity of American lobster in Nova Scotia

Lobster production per unit area of habitat varies greatly from location to location. Several physical and biological variables have previously been offered as explanations. In this study the density of ovigerous females (a proxy for egg production), postlarvae, and recruits to the fishery were measured in seven adjacent areas spanning 190 km of Nova Scotia coast. The ranking of these densities among areas persisted from year-to-year, showing consistent spatial differences in productivity. A high spatial correlation between postlarvae and fishery recruits implicated postlarvae as the proximate regulator of lobster yields. Further correlation showed that egg to postlarval survival, and not egg abundance, was related to fishery recruits. Implications for fishery management are (i) enhancement of any life-history stage between postlarvae and fishery recruits should increase fishery yields and (ii) very different levels of egg production may be necessary to maintain an equal level of fishery recruits among areas. Larval survival was highest in areas where hatching occurred late in the season; this differs from previous suggestions that early hatching promotes survival.