Research Document 1997/135

Analysis of Zn hook and line logbook data: Strait of Georgia management region

By A.R. Kronlund and K.L. Yamanaka

Abstract

Logbook data collected from the directed hook and line fishery for inshore rockfishes in the Strait of Georgia management region were evaluated for their ability to provide stock assessment information. Relative to alternative data sources, the structure of logbook data provides improved measures of fishing effort and finer spatial resolution of fishing locations. The management tactics applied to the fishery since 1986 are described and their influence on logbook data is considered. In the absence of fishery-independent indices, the utility of CPUE to index the stock is thought to be poor given the restricted mobility of rockfish relative to the capabilities of the fishing fleet (hyperstability of CPUE). Thus, it was concluded that CPUE may serve as a late warning of stock decline rather than a timely indicator.

Time series of catch per unit effort have declined throughout the Strait of Georgia region for quillback and copper rockfishes. In recent years, copper rockfish comprised a greater proportion of the landings in the Gulf Islands (statistical areas 17, 18, and 19) than formerly observed. Although the evidence is not conclusive given the available indicators, these analyses are consistent with a decline in the abundance of rockfishes, particularly in the southern Strait of Georgia. Suggestions are provided for future modeling of logbook data.

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