Evaluation of a length-based method to estimate discard rate and the effect of sampling size

TL;DR

This study reviews a length-based method for estimating discard rates in fisheries, highlighting the importance of sampling size and ship number in reducing uncertainty for compliance monitoring.

Contribution

It evaluates the effectiveness of a length-based discard estimation method and examines how sampling size influences the accuracy of discard rate estimates.

Findings

Number of ships significantly affects estimate uncertainty

Bootstrapping effectively quantifies estimation uncertainty

Sampling size impacts the reliability of discard rate estimates

Abstract

The common fisheries policy aims at eliminating discarding which has been part of fisheries for centuries. It is important to monitor the compliance with the new regulations but estimating the discard rate is a challenging task, especially where the practise is illegal. The aim of this study was to review a length-based method that has been used to estimate the discard rate in Icelandic waters and explore the effects of different monitoring schemes. The length-based method estimates the minimum discard rate and the method of bootstrapping can be used to determine the uncertainty of the estimate. This study showed that the number of ships is the most important factor to consider in order to decrease the uncertainty.