Abstract
Catch-per-unit-effort (CPUE) is often the main piece of information used in fisheries stock assessment; however, the catch and effort data that are traditionally compiled from commercial logbooks can be incomplete or unreliable due to many reasons. Pacific bluefin tuna (PBF) is a seasonal target species in the Taiwanese longline fishery. Since 2010, detailed catch information for each PBF has been made available through a catch documentation scheme. However, previously, only market landing data with a low coverage of logbooks were available. Therefore, several nontraditional procedures were performed to reconstruct catch and effort data from many alternative data sources not directly obtained from fishers for 2001–2015: (1) Estimating the catch number from the landing weight for 2001–2003, for which the catch number information was incomplete, based on Monte Carlo simulation; (2) deriving fishing days for 2007–2009 from voyage data recorder data, based on a newly developed algorithm; and (3) deriving fishing days for 2001–2006 from vessel trip information, based on linear relationships between fishing and at-sea days. Subsequently, generalized linear mixed models were developed with the delta-lognormal assumption for standardizing the CPUE calculated from the reconstructed data, and three-stage model evaluation was performed using (1) Akaike and Bayesian information criteria to determine the most favorable variable composition of standardization models, (2) overall R2 via cross-validation to compare fitting performance between area-separated and area-combined standardizations, and (3) system-based testing to explore the consistency of the standardized CPUEs with auxiliary data in the PBF stock assessment model. The last stage of evaluation revealed high consistency among the data, thus demonstrating improvements in data reconstruction for estimating the abundance index, and consequently the stock assessment.
Highlights
The catch rate or catch per unit effort (CPUE) expresses the number of fish caught with a certain amount of fishing effort; it is frequently used as an index of relative fish abundance [1]
A three-stage model evaluation was performed using methods introduced by Hinton and Maunder [32]: (1) the Akaike information criterion (AIC) and Bayesian information criterion (BIC) [31], (2) cross-validation and bootstrap [33] for estimating the overall coefficient of determination (R2), and (3) system-based testing involving the advanced Pacific bluefin tuna (PBF) stock assessment model adopted by the ISC [13]
The approach was applied in this study to estimate the number of fish in the catch according to the weight data for 2001– 2003
Summary
The catch rate or catch per unit effort (CPUE) expresses the number of fish caught with a certain amount of fishing effort; it is frequently used as an index of relative fish abundance [1]. A three-stage model evaluation was performed using methods introduced by Hinton and Maunder [32]: (1) the Akaike information criterion (AIC) and Bayesian information criterion (BIC) [31], (2) cross-validation and bootstrap [33] for estimating the overall coefficient of determination (R2), and (3) system-based testing involving the advanced PBF stock assessment model adopted by the ISC [13] These tests determined the most efficient CPUE standardization model and revealed that the data reconstruction and CPUE standardization model improved the estimation of the abundance index of PBF in Taiwan and addressed the concerns of inconsistency indicated by the ISC [27,30]
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