Publication Abstract

Evaluating local population dynamics of the American lobster, Homarus americanus, with trap-based mark re-capture methods and seabed mapping

Evaluating local population dynamics of the American lobster, Homarus americanus, with trap-based mark re-capture methods and seabed mapping

M.J. Dunnington, R.A. Wahle, M.C. Bell and N.R. Geraldi

Integration of seabed mapping, spatially referenced trapping, and mark-recapture methods can be a powerful approach for ecological studies and stock assessment. Here we evaluated the efficacy of using modified commercial lobster traps in a spatially-referenced array, along with mark-recapture methods to evaluate local population dynamics and movements of Homarus americanus on square-km scale study areas in Maine, USA. Sidescan sonar surveys of the seabed combined with diver-based population surveys, stratified by substrate type, provided a means to verify mark-recapture estimates of abundance within our study areas. Spatial referencing of trap catch permitted us to relate catch rates and lobster movements directly to seabed features. Abundance estimates from diver-based and mark-recapture based methods were similar in magnitude and seasonal changes observed by the two methods were strongly correlated. Moreover, estimates of gains (immigration) and losses (emigration and mortality) were consistent with seasonal observations reported by commercial harvesters. Catch patterns showed that lobsters caught on hard substrates had a higher degree of site-fidelity than those caught on soft-substrate. Reports of tagged lobsters from commercial fishers provided information on large scale movement patterns, suggesting that although legal lobsters travel faster than the smaller sublegals, on average, they cover less distance, likely because they are harvested. An application of this method to a habitat impact study is briefly illustrated.

Reference:

M.J. Dunnington, R.A. Wahle, M.C. Bell and N.R. Geraldi (2005) Evaluating local population dynamics of the American lobster, Homarus americanus, with trap-based mark re-capture methods and seabed mapping. New Zealand Journal of Marine and Freshwater Research 39, 1253-1276

M.J. Dunnington, R.A. Wahle, M.C. Bell* and N.R. Geraldi

New Zealand Journal of Marine and Freshwater Research 39, 1253-1276