Research Document - 2003/110

Evaluation of Research Vessel and Individual Transferable Quota (ITQ) Survey Data as Abundance Indices for Pollock

By Carruthers, E.H., Neilson, J.D., Perley, P.,
Clark, D. Smith, S.J.

Abstract

Recent pollock (Pollachius virens) assessments have been based on commercial fishery catch rates. As part of the Pollock Framework assessment, we evaluated the utility of fishery-independent data sources, such as summer research vessel and joint government/industry surveys, to develop abundance indices. Strong year effects confounded interpretation of age-disaggregated abundance indices based on data from summer RV groundfish surveys. Only very strong or weak year-classes were detectable on a year by year basis. However, when the age specific indices were summed over a year-class and compared with those obtained from the commercial catch rate information, there was some concurrence on the relative strength of year-classes. There was also broad scale agreement between trends in survey abundance and population biomass from the VPA, although survey areas do not precisely match. There was good agreement between catch rates from the RV and ITQ surveys for the proposed western management area 4Xopqrs, however it proved difficult to identify year-classes in the ITQ survey data. We concluded that the RV survey indices should be considered as an age-aggregated index in the continued development of the Framework Assessment for this species and that the ITQ survey results could be reconsidered at a later date when the survey series is longer.

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