Conservative Scoring Approach in Productivity Susceptibility Analysis Leads to an Overestimation of Vulnerability: A Study from the Hilsa Gillnet Bycatch Stocks of Bangladesh

Hiroyuki Matsuda,Hasan Faruque

doi:10.3390/fishes6030033

Hiroyuki Matsuda, Hasan Faruque

Open Access

https://doi.org/10.3390/fishes6030033

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Journal: Fishes	Publication Date: Aug 24, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: Yokohama National University, University of Dhaka

Abstract

Despite different approaches used to assign the risk scores for missing information in productivity susceptibility analysis (PSA)—a widely used semi-quantitative risk assessment tool for target and non-target fisheries stocks—for the selected attributes of a given species, no formal comparison has been made between scoring approaches in terms of how well they can predict species vulnerability. The present study evaluated the PSA findings of 21 bycatch stocks of the Hilsa (Tenualosa ilisha) gillnet fishery of Bangladesh using two different scoring approaches (the conservative scoring approach, CSA; and the alternative scoring approach, ASA) to determine the most reliable approach to minimize false estimates of species vulnerability. Our analysis revealed that the V scores increased by 0.0−0.20 with a mean value of 0.09 for 21 selected bycatches when CSA was applied. The inconsistency between the vulnerability (V)-score-suggested fishing status (V ≤ 1.8 = underfishing, V > 1.8 = overfishing) and the fishing status defined by exploitation rate (E > 0.5 = overfishing, E < 0.5 = underfishing) were 38.1% and 19.0% under CSA and ASA, respectively. Likewise, the consistency between the V-score-suggested fishing status and fishers’ perceived catch trends was found to be higher when using ASA than when using CSA. Our analysis suggests that CSA could overestimate species vulnerability. Therefore, ASA is more reliable than CSA in PSA, which may increase the confidence of fisheries stakeholders in PSA.

Highlights

The sustainable management of fisheries resources is a challenging issue for fisheries managers across the world [1]
Despite being classified as overfished by previous studies based on exploitation rate (E > 0.5), our analysis suggests that Coilia ramcarati (ZZU), Harpadon nehereus (BUC), and Rastrelliger kanagurta (RAG) are found to suffer from overfishing
Our results suggest that conservative scoring approaches (CSAs) overclassified the fishing status for an additional four species—Clupisoma garua (LUG), Mystus gulio (BMG), Otolithoides pama (OTD), and Pampus chinensis (CPO)

Summary

Introduction

The sustainable management of fisheries resources is a challenging issue for fisheries managers across the world [1]. Large-scale fisheries target species with high commercial value. These species are subject to more detailed analyses of their life-history traits, productivity, etc., and are recognized as data-rich stocks. The majority of small-scale fisheries, which account for half of the global fishery catches, are treated as data-limited fisheries [6,7]. These small-scale fisheries lack the biological and catch data, resources, and expertise required to estimate stock status using conventional quantitative stock assessment techniques [6]

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