Cod Escape Panel

Development and Trial of a Demersal Otter Trawl Cod Escape Panel

Completed April 2018

Summary

Increases in cod (Gadus morhua) abundance in the North Sea over recent years, especially in the waters around Shetland, have proved challenging for Shetland vessels undertaking the mixed demersal fishery in the area. Vessels, often with limited cod quota, can often encounter high catches of cod when targeting other species which can lead to rapid uptake of available quota.

This project involved the development of a modified trawl design that could allow some of the cod catch to escape from the net while retaining the remainder of the catch. Two identical trawls were constructed, one acting as a control using a standard net design to which catches from an experimental net could be compared. The experimental net was modified by a horizontally split extension section behind an inclined panel that guided fish upward into the top section of the extension. The lower side of the extension, beyond the inclined panel, incorporated a large mesh panel for fish to escape. The hypothesis was that cod, being powerful swimmers that are inclined to swim downwards, would swim forwards and downwards in the extension and then escape through the large mesh escape panel, while other species would fall back into the cod-end. A trawl camera system was also developed which could be deployed in the net extension.

Trials were then undertaken using the NAFC Marine Centre’s fishing vessel MFV Atlantia II to assess the effectiveness of the proposed experimental net design. Video footage provided additional information on the trawl performance and fish behaviour. The results of preliminary analysis show that overall over two-thirds of the cod catch was escaping from the experimental net compared to the control net. No consistent differences in catches of other species were recorded between the control and experimental nets.

These promising results suggest that the escape panel has strong potential as a technical measure to significantly reduce cod catches without negatively impacting on catches of other commercially important species. Further trials are recommended to determine if the experimental net design is as effective during longer tows, within different mixes of fish, and onboard larger vessels.

Funding

This project received funding as a Fisheries Local Action Group (FLAG) project through the European Marine Fisheries Fund (EMFF project SCO1711).

Download the Project Report

Development and trial of a demersal otter trawl cod escape panel (EMFF project SCO1711): technical summary (pdf)

Contact

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