Statistical estimation in cover-escape model for covered-codend experiments

Abstract

The aim of this paper is to examine from a statistical viewpoint the model and the estimation performance for covered‐codend experiments in which fish escape from the covernet. The logistic function was assumed for the selectivity curves of the codend and covernet. First, we evaluated the efficiency of the maximum likelihood (ML) estimation based on the model that considers fish escape from the covernet compared with the conventional model that does not consider the effect of fish escape. Second, we assessed the biases of the ML estimators of parameters in the codend selectivity curve by using the conventional model when fish escape occurred. Finally, we examined the performance of model selection based on the Akaike information criterion through Monte Carlo simulations. It is concluded that the model considering fish escape is effective for the analysis of selectivity. In addition, the estimator involving the model selection performed better than estimators based on fixed models. The interpretation of these results and topics of future research are also discussed.

Modelling the contact probability and size-selectivity of toothed dredges

“…The model proposed in this study is referred to as a control‐escape model. The authors have previously proposed a control‐escape model considering the covernet selectivity to obtain accurate estimates of codend selectivity from the data of covered‐codend fishing experiments in which fish escape from a covernet of insufficiently small mesh size 9,10 . The cover‐escape model is a particular one of control escape.…”

“…In each experiment, even dredges of the smallest tooth spacing used as the control gear may have been size‐selective as well as the test dredges. The authors 9,10 proposed a ‘cover‐escape model’ for estimating the trawl codend selectivity from the data of covered‐codend experiments in which fish escape from the covernet of insufficiently small mesh size. It is a case in which the covernet is referred to be incomplete as a control gear.…”