Detection of derelict creel fishing gear in Scottish waters and characterisation of whale entanglement risk

Activity: Talk / Presentation / Podcast / WebinarOral presentation

Description

Creel fisheries targeting benthic crustaceans (e.g., Nephrops) are an important Scottish fishing sector but have been implicated in accidental lethal entanglements of marine mammals and other megafauna, notably minke whales, humpback whales and basking sharks, in their groundlines and risers. Creel fleet loss rates are poorly documented but anecdotally can be considerable, at least locally. Once creel fleets are lost, little is known about the entanglement risks they continue to pose. To understand the relative risks to megafauna posed by derelict vs. operational creel fleets, better knowledge of distribution and configuration of derelict creel fleets is needed.

The CreelMap project investigated whether a combination of towed side-scan sonar (SSS) systems and Remotely Operated Vehicle (ROV) would enable efficient detection of, and characterisation of entanglement risks posed by, derelict creel fleets. Two types of SSS (EdgeTech 4125i, Klein3000) were used to survey for the presence of potential creel targets in inshore waters in western Scotland during August 2023 and May 2024, respectively. A subset of potential targets was subsequently observed directly with a BlueROV during December 2023 and June 2024.

SSS systems operating at frequencies ≥500 kHz reliably detected potential creel targets, and when operated at higher frequencies could also discriminate groundlines. However, the latter observations were strongly influenced by movements in response to seastate. The BlueROV successfully located and recorded video footage of creels in areas where SSS had previously indicated potential targets. Creels were observed as individual units as well as a (partial) fleet, the latter partially buried (thereby posing a reduced entanglement risk). Increased use of advanced robotics (e.g. micro-AUVs) may in future enable more efficient surveying for derelict creel fleets across larger, and deeper areas. Understanding how fishers dispose of derelict gears found while fishing, and development of gear recovery capacity, are important future priorities.
Period4 Sept 2024
Event titleChallenger Conference 2024, Oban
Event typeConference
LocationOban, United KingdomShow on map
Degree of RecognitionNational