Research Document - 2010/011

Impacts of Fishing Gears other than Bottom Trawls, Dredges, Gillnets and Longlines on Aquatic Biodiversity and Vulnerable Marine Ecosystems

By Donaldson, A., Gabriel, C., Harvey, B.J., and Carolsfeld, J.

Abstract

This report summarizes the literature on the impacts of 16 different fishing gear types on biodiversity and marine ecosystems. These include pots and traps, beach seine, mid-water trawl, purse, Danish and Scottish seine, trap net, weir, troll, hand picking, diving, harpoon, hook and line, cast net, and fish wheel.

The impacts described range from the straightforward (e.g. bycatch and habitat damage) to subtle (e.g. promotion of new, learned behaviours in marine mammals). The main impacts include habitat damage by crushing or entanglement by pots and traps, entanglement by the same gear of mammalian bycatch, bycatch in non-selective seine gear, and localized habitat impacts of dive and hand-picking fisheries.

Potential impacts on Vulnerable Marine Ecosystems (VME) are damage of coral or sponge by pots and traps. Danish and Scottish seines and mid-water trawls can also have significant active effects on benthic habitats as they, or parts of the gear, contacts the bottom. These effects are localized and less than that caused by active bottom gear, but could be significant if applied to patchy VME and sensitive habitats. Hand-digging and dive fisheries can also affect sensitive habitats, but these effects are generally also quite localized.

Effects on biodiversity includes cetacean, shark, and other fish bycatch in nets, cetacean entanglement in more selective pots and traps, seal and fish bycatch in traps (including endangered fish species), and turtles on hand line gear. Mid-water trawls, while quite selective through their targeted deployment, also have a significant cumulative bycatch volume. Ghost fishing by abandoned or lost gear is often quoted as a concern, particularly for pot and trap fisheries.

The range of mitigation measures being reported is broad. Gear modifications are the most common, but operational mitigation through limits on the kinds of technologies and manners of their use, temporal and spatial closures, special techniques and strategies to permit live release of bycatch, and optimized strategies to retrieve lost gear and/or render it ineffective are also key strategies. Collaborative development and implementation of mitigating strategies with the fishing fleets has been shown to be a key element to successfully addressing these questions.

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