Document de recherche 2009/109

Prises accessoires de sébastes dans les casiers à crevette des pêcheurs commerciaux en Colombie-Britannique

Par D.T. Rutherford, K. Fong, and H. Nguyen

Résumé

A sampling program to estimate rockfish bycatch in the British Columbia commercial prawn trap fishery was initiated in 2002. The bycatch sampling program utilizes the third party on-ground monitors that have already been established to collect the data necessary for the in-season management of the prawn fishery. For the rockfish bycatch program, on-ground monitors sample a sub-set of traps and record rockfish encounters to the species level. This report documents the methods and analysis, and presents results of the rockfish bycatch monitoring program from 2002 to 2008

Rockfish encounters in the commercial prawn fishery are a rare and random event and follow a Poisson distribution. The observed data was analyzed using maximum likelihood and bootstrap procedures to estimate total rockfish bycatch. Rockfish encounter rates (rockfish per trap) are presented by Pacific Fishery Management Area (PFMA) and year and ranged from a low of 0.000 to 0.045 rockfish/trap. Estimated total annual coastwide rockfish bycatch ranged from a low of 13,867 pieces in 2005 to a high of 19,996 in 2002. The coastwide estimates of rockfish bycatch at the upper 95% CI ranged from 22,792 in 2005 to 40,780 in 2002.

Twenty three species of rockfish and a total of 2088 rockfish were observed during the bycatch monitoring program from 2002 to 2008. Immature quillback rockfish (Sebastes maliger) accounted for the greatest proportion of all rockfish sampled, with an average size of 0.233 kilograms and an approximated age of 4 years. However rockfish bycatch, by species, on a coastwide basis could not be estimated due to small sample size and low encounter rates. If species composition is deemed to be an important variable that needs to be quantified with more precision, then sampling rate will have to be significantly increased along with verification of species identification.

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