A spatial method to calculate small-scale fisheries effort in data poor scenarios

Andrew Frederick Johnson,Exequiel Ezcurra,Octavio Aburto-Oropeza,Brad Erisman,Julia Corominas,Marcia Moreno-Báez,Alfredo Giron-Nava,Heather M Patterson

doi:10.1371/journal.pone.0174064

Abstract

To gauge the collateral impacts of fishing we must know where fishing boats operate and how much they fish. Although small-scale fisheries land approximately the same amount of fish for human consumption as industrial fleets globally, methods of estimating their fishing effort are comparatively poor. We present an accessible, spatial method of calculating the effort of small-scale fisheries based on two simple measures that are available, or at least easily estimated, in even the most data-poor fisheries: the number of boats and the local coastal human population. We illustrate the method using a small-scale fisheries case study from the Gulf of California, Mexico, and show that our measure of Predicted Fishing Effort (PFE), measured as the number of boats operating in a given area per day adjusted by the number of people in local coastal populations, can accurately predict fisheries landings in the Gulf. Comparing our values of PFE to commercial fishery landings throughout the Gulf also indicates that the current number of small-scale fishing boats in the Gulf is approximately double what is required to land theoretical maximum fish biomass. Our method is fishery-type independent and can be used to quantitatively evaluate the efficacy of growth in small-scale fisheries. This new method provides an important first step towards estimating the fishing effort of small-scale fleets globally.

Highlights

Global marine fisheries are under pressure from increasing demands for protein, driven by rapidly growing human populations [1,2]
San Felipe and Santa Clara in the upper Gulf of California had high Predicted Fishing Effort (PFE) values because of the high numbers of fishing boats in these communities compared with the size of their local populations
In the study area used to build our estimate of fishing effort, PFE was highest in areas of high population density, and in areas with high numbers of fishing boats relative to local human populations

Summary

Introduction

Global marine fisheries are under pressure from increasing demands for protein, driven by rapidly growing human populations [1,2]. Many commercial stocks remain either fully or over-exploited and show continued declines [3], whilst rules and regulations governing them continue to tighten, driving new fisheries development [4]. Fisheries biomass is often extracted from areas only known by fishers themselves, and is recorded at the point of landing or where the first sale of the catch is made. For this reason, fishing locations often remain elusive, off the radar and difficult to police [5]. The amount of fishing (the effort) and the area over which fishing potentially takes place (the range) are critical measures for successful fisheries management and making

Methods

Results

Discussion

Conclusion