Conservation Concerns of Small-Scale Fisheries: By-Catch Impacts of a Shrimp and Finfish Fishery in a Sri Lankan Lagoon

Benjamin L Jones,Leanne C Cullen-Unsworth,Richard K F Unsworth,Susantha Udagedara

doi:10.3389/fmars.2018.00052

Abstract

By-catch is considered a significant problem in large-scale fisheries yet in small-scale fisheries (SSF), employing >99% of the world's fishers, there is limited quantitative understanding of by-catch, and catches in general. We provide an assessment of by-catch from fishing gears (fyke, trawl, set trammel & drift trammel nets) commonly used in small-scale fisheries across the globe, using a representative Sri Lankan case study and placing this in the context of local resource use patterns. We reveal evidence of how SSF generate significant finfish by-catch with potentially significant ecological impacts. Fishers targeting shrimp (fyke, trawl and drift trammel nets) caught more non-target species than global averages (44%, 44% and 67% by weight respectively). Fishers targeting finfish (set trammel nets) caught fewer non-target species. We found that by-catch depends more on target species and gear type, supporting suggestions that SSF are not “inherently more sustainable” than their large-scale counterparts and a collective effort is required for an improved understanding of the impacts of SSF. This study highlights an additional issue of valuable food fish discards, raising questions about fisheries exploitation in the context of food security in areas where poverty and food insecurity are prevalent.

Highlights

Man’s impact on ocean diversity change is understood mainly through limited snapshots or subsamples of diversity, like charismatic organisms, commercially-important fisheries, or coral reef ecosystems (Carpenter et al, 2008; Collette et al, 2011; McClenachan et al, 2012; Ricard et al, 2012; Pauly and Zeller, 2016)
We investigate the impact of gear type and target species on by-catch and discuss some of the context-specific socio-economic factors driving resource use and fishing preference in these types of system, and use this case study as a representative lagoonal fishery to highlight the magnitude of associated small-scale fisheries (SSF) by-catch more broadly
Small-scale fisheries (SSF) contribute to the livelihoods and wellbeing of one-tenth of the world’s population (FAO, 2014), yet traditional management approaches fail to address overfishing, confounded by a poor understanding of how fishers interact with the marine environment (Fulton et al, 2011; Kittinger et al, 2014)

Summary

Introduction

Man’s impact on ocean diversity change is understood mainly through limited snapshots or subsamples of diversity, like charismatic organisms, commercially-important fisheries, or coral reef ecosystems (Carpenter et al, 2008; Collette et al, 2011; McClenachan et al, 2012; Ricard et al, 2012; Pauly and Zeller, 2016). The same applies to the impacts of the words fishing gear, where the majority of what we know comes from studies of large-scale fisheries, where overexploitation, bycatch, and habitat destruction are commonly encountered and well-documented (Dayton et al, 1995; Hutchings, 2000; Dulvy et al, 2003; Kappel, 2005; Lotze et al, 2006; Polidoro et al, 2012; Zeller et al, 2017). In comparison, limited attention has been paid to small-scale fisheries (SSF) (Fennessy and Everett, 2015; Temple et al, 2017) which are assumed to have low discard rates, for example around 3.7% total catch (Kelleher, 2005)

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