Reduction of fish by-catch in shrimp trawl using a rigid separator grid in the aft belly

Isaksen, Bjørnar; Valdemarsen, John Willy; Larsen, Roger B.; Karlsen, Ludvig

doi:10.1016/0165-7836(92)90086-9

Cited by 148 publications

(157 citation statements)

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“…In all cases grids designed specifically for a given species have been observed to outperform other grids and codend designs (Isaksen et al, 1992;Anonymous, 1998). Nevertheless, direct comparison is difficult, because the design and the bar spacing have varied with the specific design for each individual fishery.…”

Section: Resultsmentioning

confidence: 99%

“…6). Installation was performed according to Isaksen et al (1992) and Ercoli et al (2000). All the grids and the square mesh panel allowed juveniles a direct outlet to escape from the codend except in version B, in which small fish passing through the grid were directed into the codend, while larger fish were directed into an extra codend on the upper portion of the net (see Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Technology based on fish sorting grids was developed in different parts of the world in the 1990s for various purposes, ranging from excluding large protected species such as sharks and turtles (Villaseñor, 1997) to allowing the escape of juveniles, in particular hake, in South America (Ercoli et al, 1997), or pelagic species (Kvalsik et al 2002), as well as merely separating certain species of crustaceans, e.g. shrimps (Isaksen et al, 1992, Broadhurst et al, 1996Ercoli et al, 1997;Polet, 2002;Graham, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Preservation of juvenile hake (<i>Merluccius merluccius</i> L) in the western Mediterranean demersal trawl fishery by using sorting grids

Sardà¹,

Molı́²,

Palomera³

2004

Sci. Mar.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Preservation of juvenile hake (<i>Merluccius merluccius</i> L) in the western Mediterranean demersal trawl fishery by using sorting grids

Sardà¹,

Molı́²,

Palomera³

2004

Sci. Mar.

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“…When the density of juveniles in the fishing grounds is large, the catches of juveniles of various fish species can be large. The Nordmøre grid ( Figure 1) has been proven to be efficient at excluding bycatch fish species during shrimp trawling (Isaksen et al 1992). With the introduction of the requirement for its use in the Norwegian fishery in 1991 and internationally in 1993, the bycatch problem of larger-sized fish was eliminated because they are unable to pass through the grid and into the trawl cod end.…”

mentioning

confidence: 99%

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

et al. 2017

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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

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“…a narrow selection range (SR; the di erence in length between the 25 and 75% capture probabilities), is preferred. Rigid sorting grids were rst introduced into shrimp trawl sheries to reduce the by-catch of turtles (Watson and McVea, 1977) and juvenile sh (Isaksen et al, 1992). Grids were later modi ed to perform as size selective devices (Larsen and Isaksen, 1993) and a large number of size selective grid designs have been tested in a variety of sheries (Anon, 1998).…”

Section: Introductionmentioning

confidence: 99%

Size selection of cod by rigid grids—Is anything gained compared to diamond mesh codends only?

et al. 2006

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Size selective grids were introduced into the Barents Sea demersal trawl shery in 1997. It was believed at the time that in comparison to standard diamond mesh codends, grids had better selective properties, i.e. narrower selection range. Few studies have directly compared the selective properties of the combined grid and codend with that of the codend only. In this study we describe two experiments carried out in 2002 and 2003, where we directly compared the properties of codend selectivity for cod (Gadus morhua ) with the combined selectivity of a Sort-V grid and a codend. In 2002 we used small-meshed covers, whereas the twin trawl method was used in 2003. In both experiments we compared the selectivity of a 135 mm codend only with that of a trawl tted with a 135 mm codend and a 55 mm grid, which is the mandatory con guration. In 2003 we also estimated the selectivity of a 155 mm diamond mesh codend, having an L 50 similar to that of the grid and 135 mm codend combination. The results presented no evidence that the grid and mesh combination had sharper size selection than codend meshes. The introduction of the mandatory use of grid in the shery in 1997 therefore only increased L 50 , and corresponded to a mesh size increase of around 20 mm. Mean selection length of the grid was inversely related to catch rates in the 2002 experiment when large catches were taken. Grid selection appeared less a ected by seasonal variations in degree of stomach fullness or condition than mesh selectivity. Other situations where grid selection might perform better than mesh selection are discussed.

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Reduction of fish by-catch in shrimp trawl using a rigid separator grid in the aft belly

Cited by 148 publications

References 0 publications

Preservation of juvenile hake (<i>Merluccius merluccius</i> L) in the western Mediterranean demersal trawl fishery by using sorting grids

Preservation of juvenile hake (<i>Merluccius merluccius</i> L) in the western Mediterranean demersal trawl fishery by using sorting grids

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

Size selection of cod by rigid grids—Is anything gained compared to diamond mesh codends only?

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