Censored catch data in fisheries stock assessment

Type Article
Date 2005-09
Language English
Author(s) Hammond T2, Trenkel VerenaORCID1
Affiliation(s) 1 : IFREMER, Dept EMH, F-44311 Nantes, France.
2 : 9 Grove Street, PO Box 1012, Dartmouth, N.S., Canada, B2Y 3Z7
Source ICES Journal of Marine Science (1054-3139) (Elsevier), 2005-09 , Vol. 62 , N. 6 , P. 1118-1130
DOI 10.1016/j.icesjms.2005.04.015
WOS© Times Cited 20
Keyword(s) Stock assessment, Misreporting, Discarding, Censored data
Abstract Landings statistics can be lower than true catches because many fish are discarded or landed illegally. Since many discards do not survive, treating landings as true catches can lead to biased stock assessments. This paper proposes treating catch as censored by bounding it below by the landings, L, and above by cL (for scalar c > 1), We demonstrate the approach with a simulation study, using a Schaefer surplus production model. Parameters were estimated in a Bayesian framework with BUGS software using two sets of priors. Both the traditional true-catch method and a survey-and-effort method (which was landings free) performed worse on average than the censored approach, as measured by the Bayes risk associated with estimates of maximum sustainable yield (MSY) and of an index of depletion (X). Recursive partitioning (regression trees) was used to associate simulation parameters to best-performing methods, showing that higher commercial fish catchability favoured the censored method at estimating X. In conclusion, censored methods provide a means of dealing with discarding and misreporting that can outperform some traditional alternatives.
Full Text
File Pages Size Access
publication-641.pdf 31 235 KB Open access
Top of the page