January 4, 2011
Principal Investigator: Karen Martien, Marine Mammal Genetics Group
The Catch Limit Algorithm (CLA) is the method by which the International Whaling Commissions calculates the number of whales that can be safely hunted from a given stock. Though the CLA was rigorously tested prior to its adoption, most of those original performance trials focused on single-stock scenarios, and none of them considered the possibility of two populations with ongoing dispersal among them. We used simulation performance tests conduct within the TOSSM package framework to examine the performance of the CLA under a variety of population structure scenarios. Ours is the first study to investigate the levels of connectivity (i.e., dispersal rate) for which populations require separate management in order to meet the conservation goals of the CLA. We found that the CLA is vulnerable to errors in stock definition even when dispersal rates are as high as 0.5% per year, highlight the value of spatially-diffuse harvest patterns that avoid potential overharvest of unrecognized stocks and the need for powerful genetic methods in order to accurately identify stocks.
Martien, K.K., D. Gregovich, M.V. Bravington, A.E. Punt, A.E. Strand, D.A. Tallmon, B.L. Taylor. 2009. TOSSM: an R package for assessing performance of genetic analytical methods in a management context. Molecular Ecology Resources 9:1456-1459.