Artificial light improves escapement of fish from a trawl net

Abstract

The elimination of unwanted catch in mixed species fisheries is technically challenging given the complexity of fish behaviour within nets. Most approaches to date have employed technologies that modify the nets themselves or use physical sorting grids within the gear. There is currently increasing interest in the use of artificial light to either deter fish from entering the net, or to enhance their escapement from within the net. Here, we evaluated the differences in catch retained in a standard otter trawl, relative to the same gear fitted with a square mesh panel, or a square mesh panel fitted with LEDs. We found that the selectivity of the gear differed depending on water depth. When using a square mesh panel in shallow depths of 29–40 m the unwanted bycatch of whiting and haddock was reduced by 86% and 58% respectively. In deep, darker water (45–95 m), no change in catch was observed in the square-mesh panel treatment, however when LEDs were added to the square-mesh panel, haddock and flatfish catches were reduced by 47% and 25% respectively. These findings demonstrate the potential to improve the performance of bycatch reduction devices through the addition of light devices to enhance selectivity. The results also highlight species-specific and site-specific differences in the performance of bycatch reduction devices, and hence a more adaptive approach to reduce bycatch is probably required to maximize performance.

Artificial light improves size selection for northern shrimp (Pandalus borealis) in trawls

“…The use of light to reduce catches of unwanted species has gained interest in different fisheries in the last years (Nguyen and Winger 2018;Southworth et al 2020). Shrimp have been believed to show limited behavioural response to the various trawl components during the capture phase (High et al 1969;Wardle et al 1993;Hannah and Jones 2003).…”

Relative Catch Performance of Two Gear Modifications Used to Reduce Bycatch of Undersized Fish and Shrimp in Mediterranean Bottom Trawl Fisheries

“…Solutions to increase selection in bottom trawls can alternatively be based on modifications to the body of the trawl by using panels of different meshes (Campos and Fonseca 2004), changing the cod end mesh netting (Deval et al 2016), or fitting bycatch reduction devices (Fonseca et al 2005;Aydın et al 2011). Among the solutions tested, square mesh panels (Campos and Fonseca 2007), selective grids (Fonseca et al 2005;Vitale et al 2018b) or escape light rings (Southworth et al 2020) have shown good technical results, with an observed decrease in the fraction of unwanted bycatch of at least some commercial target species. In addition to good selection properties, desirable properties of bycatch reduction devices are low cost, ease of operation, low environmental impact, being easily enforceable, and having acceptable losses of commercial fish fractions (Catchpole et al 2008).…”

Catch yield and selectivity of a modified scallop dredge to reduce seabed impact

“…Reduction of their capture by the fishery would therefore be desirable. One method that has been demonstrated to reduce capture of fish in a queen scallop trawl fishery is the inclusion of artificial light on trawl nets which significantly reduce bycatch of haddock and flatfish [ 44 ]. Similarly, a study focusing on the reduction of flatfish bycatch in an ocean shrimp ( Pandalus jordani ) trawl fishery found that adding LED lights on the trawl fishing line reduced bycatch of sole by up to 69% [ 45 ].…”