Derelict Fishing Line Provides a Useful Proxy for Estimating Levels of Non-Compliance with No-Take Marine Reserves

Abstract

No-take marine reserves (NTMRs) are increasingly being established to conserve or restore biodiversity and to enhance the sustainability of fisheries. Although effectively designed and protected NTMR networks can yield conservation and fishery benefits, reserve effects often fail to manifest in systems where there are high levels of non-compliance by fishers (poaching). Obtaining reliable estimates of NTMR non-compliance can be expensive and logistically challenging, particularly in areas with limited or non-existent resources for conducting surveillance and enforcement. Here we assess the utility of density estimates and re-accumulation rates of derelict (lost and abandoned) fishing line as a proxy for fishing effort and NTMR non-compliance on fringing coral reefs in three island groups of the Great Barrier Reef Marine Park (GBRMP), Australia. Densities of derelict fishing line were consistently lower on reefs within old (>20 year) NTMRs than on non-NTMR reefs (significantly in the Palm and Whitsunday Islands), whereas line densities did not differ significantly between reefs in new NTMRs (5 years of protection) and non-NTMR reefs. A manipulative experiment in which derelict fishing lines were removed from a subset of the monitoring sites demonstrated that lines re-accumulated on NTMR reefs at approximately one third (32.4%) of the rate observed on non-NTMR reefs over a thirty-two month period. Although these inshore NTMRs have long been considered some of the best protected within the GBRMP, evidence presented here suggests that the level of non-compliance with NTMR regulations is higher than previously assumed.

Bigger or better: The relative benefits of protected area network expansion and enforcement for the conservation of an exploited species

“…Notably, many PA networks today have low levels of enforcement-that is, measured compliance is low-even in relatively well-managed conservation contexts. For example, the marine reserve network on Australia's Great Barrier Reef already covers >30% of reef area, but illegal harvesting has been estimated at 32.4% of comparable nearby unprotected reefs (Williamson, Ceccarelli, Evans, Hill, & Russ, 2014). Similarly, in the 1970-1980 ′ s, 75% of Zambian elephant populations were lost in the Luangwa Valley because, despite substantial investments in anti-poaching patrols, enforcement effort was spread too thinly to stop poachers (Leader-Williams & Albon 1988;Leader-Williams, Albon, & Berry, 1990).…”

Effectiveness of shore‐based remote camera monitoring for quantifying recreational fisher compliance in marine conservation areas

“…, ). Indirect observation involves quantifying signs of illegal activity, such as blast craters on coral reefs or discarded fishing line (Williamson, Ceccarelli, Evans, Hill, & Russ, ). These techniques are rarely used, and quantifying non‐compliance during specific temporal periods is challenging (Williamson et al .…”

A social–ecological approach to assessing and managing poaching by recreational fishers

“…For instance, quantifying derelict (lost or discarded) fishing gear inside and outside of no‐fishing reserves can provide robust evidence of poaching, and a relative measure of fishing effort in each area (Williamson et al . ).…”

“…The Great Barrier Reef Marine Park (GBRMP; Panel 1 and Figure ) is widely considered one of the best managed marine ecosystems in the world, but substantial amounts of poaching by fishers still occurs (Arias and Sutton ; Williamson et al . ; GBRMPA ). Studying poaching in the GBRMP is a major challenge.…”