FIRST PROJECTIONS OF AMERICAN LOBSTER FISHERY RECRUITMENT USING A SETTLEMENT INDEX AND VARIABLE GROWTH

摘要

Standardized suction sampling techniques were used to monitor postlarval settlement of Homarus americanus H. Milne-Edwards, 1837 at selected cobble nursery sites in mid-coast Maine and Rhode Island from 1989-2001. Inter-annual variations in settlement (high and low densities) were common in both regions, but from 1995 through 2000 only low settlement densities were recorded in the study area in Maine. This was reversed in 2001 with record high settlement. We show that settlement strength determines cohort abundance at least to age one before lobsters disperse from nurseries. However, because of variable growth rates and the 4-9 yr time lag between settlement and fishery recruitment, it has been difficult to assess the impact of inter-annual differences in settlement on future fishery trends. This is the first attempt to provide population projections based on initial settlement data for the American lobster. We developed a growth model that projects the impact of the observed settlement patterns on future fishery landings. The model incorporates variations in individual growth rates obtained from prior field and laboratory studies. Growth variability masks most of the observed inter-annual fluctuations in settlement, but not multiple years of low values. The projections assume no density-dependence following settlement and that sites sampled are representative of settlement trends over a significant area. The growing time series will provide an assessment of the model and its assumptions over the next several years, thereby testing the efficacy of using settlement as an early warning of population changes in this species.