Untangling the Problem of Abandoned, Lost, and Discarded Fishing Gear: Evaluating the Benefits of Side Scan Sonar as a Gear Detection Method
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Abandoned, lost, or otherwise discarded fishing gear (ALDFG) has surfaced as a significant conservation issue that continues to compromise the economic, social, and ecological aspects of the marine environment. To alleviate these concerns, methods of gear detection can be applied to increase the precision of derelict gear retrieval and potentially improve the likelihood of success. Targeted in Canada's most productive American lobster (Homarus americanus) fishing area, 27 side scan sonar (SSS) transects were conducted in LFA 34 over a 12-day survey period in Clark’s Harbour, Nova Scotia, to evaluate the benefits of gear detection in large-scale retrieval missions. By conducting spatial analysis, results show that a hotspot of reported gear losses is strong in Clark’s Harbour. Following a comprehensive review of the SSS data, 114 potential ALDFG contacts were visually identified, and only one item was confirmed retrieved. Despite this, a large volume of ALDFG was retrieved in areas where there was no SSS coverage based on fisher’s local knowledge. This finding indicates retrieval efforts without the use of SSS can yield a high rate of ALDFG removal success. While gear can be located using SSS, greater grappling precision and full coverage SSS surveys is recommended at smaller geographic scales, such as sensitive benthic areas. Organizations should consider the cost of SSS surveys versus retrieval missions based on fisher’s knowledge in future applications. Keywords: American lobster; Southwest Nova Scotia; Clark’s Harbour; ghost gear; ALDFG; gear detection; side scan sonar; gear retrieval missions; geospatial analysis; cost-benefit analysis; fisheries management.
Fulton, L., 2021. Untangling the problem of abandoned, lost, and discarded fishing gear: Evaluating the benefits of side scan sonar as a gear detection method [graduate project]. Halifax, NS: Dalhousie University.