Size selection of Atlantic cod, haddock and pollock (saithe) by otter trawls with square and diamond mesh codends of 130–155mm mesh size

Halliday, R. G.; Cooper, C.G.; Fanning, Paul; Hickey, W.M.; Gagnon, Pierre

doi:10.1016/s0165-7836(99)00020-x

Cited by 30 publications

(7 citation statements)

References 9 publications

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“…However, other authors have found no significant correlation between mesh size and selection range (Reeves et al, 1992;Halliday et al, 1999). The possibility of achieving "grid selection" by increasing mesh size, and the relationship between mesh size and selection range, should be studied in an experiment that compares the selection of a 135 mm mesh size codend, a codend of a larger mesh size and the total selection of a trawl with a grid and a 135 mm mesh size codend.…”

Section: Discussionmentioning

confidence: 97%

Total selectivity of a commercial cod trawl with and without a grid mounted: grid and codend selectivity of north-east Artic cod

Kvamme¹,

Isaksen²

2004

Fisheries Research

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Section: Discussionmentioning

confidence: 97%

Total selectivity of a commercial cod trawl with and without a grid mounted: grid and codend selectivity of north-east Artic cod

Kvamme¹,

Isaksen²

2004

Fisheries Research

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“…However, the mean selection length of the 55 mm bar spaced grid system is higher than that of the 135 mm codend. If SR increases with increasing mesh size as indicated in the review of selectivity experiments for cod by Halliday et al (1999), the di erence in SR of the grid system and a codend with equal L 50 would likely be somewhat underestimated. The L 50 estimates for grid and for grid and codend combined showed consis-tent values across surveys.…”

Section: Discussionmentioning

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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“…The fishery, besides a variety of roundfish species, also includes important flatfish species. Since diamond mesh codends are typically more selective for flatfish than for roundfish species [ 48 – 50 ] a square mesh codend design (CD S ) was also considered ( Fig 1 ). The design guides made by Tokaç et al [ 51 ] showed that a 60 mm mesh size with an opening angle of 90° would result on a L 50 of approximately 25 cm for hake.…”

Section: Methodsmentioning

confidence: 99%

Optimizing size selectivity and catch patterns for hake (Merluccius merluccius) and blue whiting (Micromesistius poutassou) by combining square mesh panel and codend designs

Cuende¹,

Sistiaga

Herrmann

et al. 2022

PLoS ONE

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Gear modifications in fisheries are usually implemented to obtain catch patterns that meet management objectives. In the Basque bottom trawl fishery, gear regulations include the use of a square mesh panel (SMP) placed at the top panel of the extension piece of the trawl to supplement diamond mesh codend selectivity. However, the catch patterns obtained with this combination have raised concern among scientists and authorities. This study combines new data on different SMP and codend designs with existing data from the literature to produce new results that are applied to predict the size selectivity and catch patterns of different gear combinations for a variety of fishing scenarios. A systematic approach based on the concept of treatment trees was outlined and applied to depict the effect of individual and combined gear design changes on size selectivity and catch patterns for hake (Merluccius merluccius) and blue whiting (Micromesistius poutassou). This approach led to identification of the gear combination with the most appropriate exploitation pattern for these two species and improved the readability and interpretation of selectivity results. The results demonstrated that changes both in SMP and, especially, codend designs have a significant effect on hake and blue whiting size selectivity and catch patterns. Therefore, we believe that further research should prioritize codend size selectivity, and additional selection devices may be added once codend designs with good selective properties are achieved.

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Size selection of Atlantic cod, haddock and pollock (saithe) by otter trawls with square and diamond mesh codends of 130–155mm mesh size

Cited by 30 publications

References 9 publications

Total selectivity of a commercial cod trawl with and without a grid mounted: grid and codend selectivity of north-east Artic cod

Total selectivity of a commercial cod trawl with and without a grid mounted: grid and codend selectivity of north-east Artic cod

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

Optimizing size selectivity and catch patterns for hake (Merluccius merluccius) and blue whiting (Micromesistius poutassou) by combining square mesh panel and codend designs

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