Academic journal article Journal of Sustainable Development

The Backward-Bending Supply Curve in Fisheries-Revisited

Academic journal article Journal of Sustainable Development

The Backward-Bending Supply Curve in Fisheries-Revisited

Article excerpt

Abstract

This study discusses and estimates the backward-bending supply curve, using data for three years over a six-year time span from the inshore purse seine fishery in Khanh Hoa province, Vietnam. Four different models are developed for estimation based on fisheries data, in the absence of stock survey data. The estimated maximum sustainable yield for the anchovy in south-central Vietnam ranges from 138 thousand tons to 293 thousand tons. The results reveal that the anchovy stock to some extent is biologically over-exploited, but seems to have rebuilt in recent years. For management it makes sense to use available, cheaply collected fisheries data on harvests, prices and costs, if biological surveys are lacking, which is often the case due to the cost of establishing expensive research capacities and time series.

Keywords: backward-bending supply, inshore purse seine fishery, maximum sustainable yield, overfishing, supply function

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1. Introduction

Overfishing is a huge problem in many developing countries (Pomeroy, 2012; Stobutzki, Silvestre, & Garces, 2006), resulting in a severe depletion of coastal fish stocks. This problem is also mounting in developed countries (Flaaten, 2013; Organisation for Economic Co-operation and Development [OECD], 2012). To address and solve the problem of overfishing, stock assessment is often considered important from both a biological and a fisheries perspective. However, biological surveys are expensive and take years and may be unrealistic especially for developing countries.

The backward-bending supply curve for open-access fisheries has received little attention in recent years. The original study was introduced by Copes (1970). Clark (1990) refers to a discounted supply curve which is also a backward-bending one, but for the optimal managed fishery. The most recent study on estimation of a supply function, to the best of our knowledge, is that of Nostbakken and Bjorndal (2003), using data of the North Sea herring fishing industry. They discuss substantial impacts of different regulatory regimes-open-access fishery and optimal managed fishery-on the supply of the North Sea herring fisheries.

The purpose of this paper is to assess fisheries' health in the case of limited information. We show how fisheries data and bioeconomic theory for open-access fisheries can be applied in order to make assessments when no reliable stock assessment data is available. First, we discuss theoretically the backward-bending supply curve. Second, we estimate the supply curve using fisheries data for three years across a six-year time period (2005, 2008, 2011) of the inshore purse seine fishery in Khanh Hoa province, Vietnam. Third, we identify the biological stock development of the anchovy species, which is a major resource for this fishery. Fourth, the overfishing issue for this inshore purse seine fishery is analysed.

The findings of this study indicate that the harvests are beyond the maximum sustainable yield (MSY). Furthermore, the harvests show a decreasing trend over the six-year period. This suggests that the stock is over-exploited, but on a path to being rebuilt. The short lifespan and high reproduction of the anchovy are probably the reasons behind this development. Hence, to say that the inshore waters in Vietnam are severely depleting is not supported in our findings and should be reconsidered.

The rest of the paper is divided into the following sections. The next section gives a brief description of the overfishing problem and the inshore purse seine fishery in the Khanh Hoa province, Vietnam. This is followed by a modelling section on supply functions, developed to estimate the backward-bending supply curve. Then comes a presentation of data and a section on empirical analysis with the estimation models for the backward-bending supply curve for this fishery. In the ensuing two sections, the results are presented and discussed in relation to the problem of overfishing of the actual fishery and in similar fisheries. …

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