Research Document - 2002/108

At-sea observer coverage for catch monitoring of British Columbia hook and line fisheries

By R. Haigh, J. Schnute, L. Lacko, C. Eros, G. Workman, B. Ackerman

Abstract

This paper takes an initial look at the hook and line observer data and is exploratory. It provides several methodologies for calculating the total catch of IRF species by the hook and line fisheries: (i) the adjustment of landed IRF catch using observed discard rates, (ii) the prediction of total IRF catch from landed target catch, and (iii) the extrapolation of observed catch to total catch, with estimates of precision from simple random sampling theory. While the latter methodology is sound in principle, the limited availability of data and the low levels of observer coverage lead to highly biased estimates of total catch with enormous confidence intervals. Levels of observer coverage needed to attain target precision levels are derived based on theavailable set of observer logs. Because the current low levels of coverage are insufficient to characterize the underlying fisheries, estimates of catch and coverage derived should not be usedfor management purposes.

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