Install exclusion devices on fishing gear: Snakes & lizards
Overall effectiveness category Awaiting assessment
Number of studies: 1
Background information and definitions
Aquatic reptiles may become trapped or entangled in fishing nets (e.g. trawl nets, hoop nets, fyke nets) and traps. Exclusion devices, such as grids, mesh, funnels, rings, or rectangular inserts, can be installed in an attempt to reduce the number of non-target animals that are caught.
Due to the number of studies found, this action has been split by species group. See here for: Sea turtles; Tortoises, terrapins, side-necked & softshell turtles or Crocodilians.
For studies that discuss the effect of using devices that allow reptiles to escape from fishing gear, see Install escape devices on fishing gear, and for studies on the effect of using a combination of exclusion and escape devices see Install exclusion and escape devices on fishing gear.
Supporting evidence from individual studies
A replicated study in 2012 in off the coast of Western Australia (Wakefield et al. 2017) found that exclusion grids with escape hatches (‘bycatch reduction device’) did not prevent sea snakes from entering the codend of trawl nets in a tropical teleost fishery. In total 331 of 351 sea snakes passed through the exclusion grid, however only 16 sea snakes were recorded as trawl catch. The authors note that sea snakes were observed escaping through the trawl net and may have done so after passing through the grids. Loss of commercially-targeted teleost species from all trawls was 1% of catch. In June–December 2012, catch (target and unwanted) from three commercial trawl vessels was monitored using in-net and onboard cameras during daylight. Vessels were fitted with either: upward-facing grid and escape hatch with diamond-mesh net (372 trawl hours on 2 vessels), downward-facing grid and escape hatch with diamond-mesh net (559 trawl hours on 2 vessels), or downward-facing grid and escape hatch with square mesh net (389 trawl hours on 1 vessel; see original paper for all specifications). Use of bycatch reduction grids with escape hatches was mandatory in this fishery from 2006.Study and other actions tested
Referenced paperWakefield C.B., Santana-Garcon J., Dorman S.R., Blight S., Denham A., Wakeford J., Molony B.W. & Newman S.J. (2017) Performance of bycatch reduction devices varies for chondrichthyan, reptile, and cetacean mitigation in demersal fish trawls: assimilating subsurface interactions and unaccounted mortality. ICES Journal of Marine Science, 74, 343-358.