Globally, gill netting is the most commonly deployed fishing gear and a particularly common fishing method used in small-scale, coastal fisheries around the world. Gill netting often results in high bycatch rates, where non-target species who also use the inshore coastal waters (such as sea turtles, small cetaceans and seabirds), become entangled in the nets and drown. For cetaceans, it is estimated that 98% of bycatch globally are caught in gill nets (Read et al 2016).

Bycatch like this damages fishers’ equipment and can lead to expensive replacements, or days of down time spent repairing nets instead of fishing. It is also life threatening for the individual marine animals accidentally entangled, and can lead to significant reductions in their local populations. Sometimes the bycatch rate reduces the conservation status of a species, which can lead to the introduction of fisheries management measures such as closing areas to fishing, either seasonally or permanently

Investigating alternative solutions

Fishery measures such as closed areas, effort reduction, gear switching or seasonal fishing restrictions with the aim of reducing bycatch are deeply unpopular with fishers. Such fishery measures usually impact the fishers economically and so resistance to these legislative measures is often high resulting in slow implementation (over decades). Moreover, once implemented, legislative measures typically suffer low compliance – especially if monitoring and enforcement, is not adequately resourced (as is often the case).

Technical measures applied to existing fishing gear to make them more selective are favoured by fishers as a means to reduce bycatch as they generally allow fishing practices to continue unchanged whilst simultaneously achieving the desired conservation outcome meaning fisher engagement and compliance is higher.

In an attempt to provide a technical alternative to legislative means, more recent bycatch mitigation science has focussed on understanding marine animals’ reactions to sensory deterrents. For example, using technological devices to emit visual, audio and acoustic warnings that the nets are in place, and encouraging non-target species to avoid them.
For example, a recent study (Bielli, et al., 2019) deployed light emitting diodes (LEDs), as a visual cue, on the floatlines of paired gillnets in Peru. Their results found that this approach could be very effective at reducing the bycatch of a variety of non-target marine animals.

In their experiment, for illuminated nets, bycatch probability was reduced by up to 74 % for sea turtles and 71 % for small cetaceans in comparison to non-illuminated, control nets. For seabirds, bycatch rates decreased by 84 % in the presence of the LEDs. In addition, they found that target species catch rate was not negatively affected by the presence of LEDs. This work confirms findings of earlier studies in Peru (Ortiz et al. 2016) and Mexico (Wang et al 2013 & 2010).

To date the LEDs available for scientific trials have been rudimentary. They have emitted light and have been sufficient for the needs of the trials, however they have not been quickly adopted by fishermen because they are expensive, unreliable, impact the fishing operations (snag lines, difficult to attach etc). The costs and extra effort involved outweighed the benefits to the fishers.

A simple, cost effective solution

Based on the growing body of evidence that illumination of fishing gear can effectively reduce marine bycatch, Fishtek Marine’s experienced engineers have developed a new, low cost product specifically designed around the needs of the fishers. The NetLight.

NetLight is a small, long lasting, robust device that can easily be attached to the ropes on fishing nets in order to alert sea turtles, small cetaceans and seabirds to the presence of the net and enable them to avoid entanglement.

Unlike closing areas to fishing, and setting seasonal restrictions, NetLights can be implemented without negative impacts on the fishers’ target catch rates. Moreover, fishers’ needs have been considered in the design so NetLight devices are easy to use, robust, and cheap to buy and maintain.

Given that NetLight is extremely robust, we also can comfortably recommend it’s use for increasing the selectivity of trawls. In the Pink Shrimp Fishery (Oregon, USA), a green LED light is mandated for use in order to mitigate smelt bycatch. LED lights attached to the footrope of the shrimp trawl reduced smelt bycatch by 90%. Fishers in this fishery complain that the existing lights available are expensive and prone to failure. Fishtek’s NetLight offers a viable, robust and cost-effective alternative. Get in touch!