Research Document - 2016/103

Context and reinterpretation of reported redfish catch in Unit 1+2 in the 1980s and 1990s based on interviews with industry participants

By Duplisea, D.E.

Abstract

Previous model fitting exercises have revealed difficulties reconciling catch data with declines in biomass for Unit 1+2 redfish in the late 1980s and early 1990s. A series of interviews with redfish fishing industry participants from the 1980s and 1990s was conducted primarily to show how fish was caught, how much was caught and what was the composition of the catch at this time. Quasi-quantitative indicators of total fish catch and composition were determined from these interviews and suggest that the DFO reported catch data may underestimate total catch in this period by more than a factor of 2. Catch composition reported to DFO from this period shows only a very small percentage of fish <20 cm while these indicators suggest that 45-76% of the catch abundance in this period may have been constituted by fish <20 cm. It is assumed that because none of the fishermen's activities were prohibited during this period, and the fact that most have long since left the fishery, this information may be relatively unbiased. It is not suggested that reported catch data should be modified based on information from this study. This study is still too much of a patchwork of non-randomly sampled information to be considered a valid quantitative means of correcting these data hence the term quasi-quantitative is used throughout the document to describe the indicators developed here. Despite not being able to correct catch data using this study, the present work provides context for interpretation and possibly constraining model fitting results for this period.

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