Performance of the Nordmøre Grid in Shrimp Trawling and Potential Effects of Guiding Funnel Length and Light Stimulation

Abstract

The introduction of the Nordmøre grid to shrimp trawls has reduced the issue of bycatch to that of smallsized species and juveniles that are able to pass through the grid and enter the small-meshed cod end together with the targeted shrimp. This study estimated the size-and species-selective performance of the Nordmøre grid in the configuration most often applied by fishermen and made a preliminary exploration of the effects of reducing the length of the guiding funnel in front of the grid and mounting light-emitting diodes (LEDs) around the escape exit. Experimental fishing trials were conducted in the Barents Sea to assess the size-selective properties of a 19-mm bar spacing Nordmøre grid, mandatory in this Norwegian trawl fishery targeting deepwater shrimp Pandalus borealis (also known as northern shrimp), and its potential improvement. Results were obtained for the target species and four bycatch species: redfish Sebastes spp., Haddock Melanogrammus aeglefinus, Atlantic Cod Gadus morhua, and American Plaice Hippoglossoides platessoides. In general, very few deepwater shrimp were found to escape through the escape exit, although the quantity increased slightly at larger sizes. Between 80% and 100% of the bycatch species up to a species-specific size passed through the grid and entered the cod end. A short guiding funnel decreased this for Haddock significantly by increasing the fraction of small Haddock seeking the escape exit. Further, adding LEDs around the escape exit significantly negated this effect. For the other bycatch species, the results indicated similar trends but were not statistically significant. However, considering that

Investigating fish behavioural responses to LED lights in trawls and potential applications for bycatch reduction in the Nephrops-directed fishery

“…As a result, most fish, which previously tried to avoid the grid, swam through it and were caught. Similar results were obtained by Larsen et al (2017), who used lights to highlight the escape opening in a Nordmøre grid. Grimaldo et al (2017) tested lights on free moving ropes in a square mesh section to increase the contact probability of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) with the netting; thus, enhancing their escape rate.…”

“…Such cases are frequent and have been reported before (e.g. Larsen et al, 2017). Therefore, we were confident that all the models could be used to describe the vertical separation efficiency.…”

The effects of different artificial light wavelengths on some behavioural features of juvenile pelagic Atlantic horse mackerel, Trachurus trachurus (Actinopterygii: Perciformes: Carangidae)

“…Consequently, the use of artificial light device with such specific wavelength(s) could play key role essentially to mitigate the catch of such fish juveniles. Recent workers (Hannah et al 2015, Larsen et al 2017, Melli et al 2018) have shown artificial lights as very capable of reducing bycatch during commercial fisheries activities. In this context, it is very pertinent that workers in this specialist endeavour continue to improve their knowledge about behavioural responses of fish species toward artificial light wavelengths.…”

Population structure, size at first sexual maturity, and feeding ecology of Conodon nobilis (Actinopterygii: Perciformes: Haemulidae) from the coasts of Pernambuco, north-eastern Brazil

“…Previous studies in the region have shown that the bulk of the catch of the shrimp fishery in Pernambuco shares the same feeding ground and season of reproduction (e.g., between October and March) (Lopes et al 2014, 2017, 2018, Silva Júnior et al 2015, Eduardo et al 2018b) and a closed season could be established during the austral summer. In addition, the application of BRD (e.g., fisheye, grid and square mesh) used to exclude fish and other small bycatch from the trawl (Broadhurst 2000, Eayrs 2007, Larsen et al 2017) might be a good conservation tool. Some initiatives that are limited by the lack of information occur in this region, such as the experimental use of bycatch reduction technologies (Anonymous 2018) and Marine Protected Areas (e.g., APA Guadalupe), which still has no management plan.…”