scholarly journals Bycatch reduction in the deep-water shrimp (Pandalus borealis) trawl fishery by increasing codend mesh openness

2021 ◽  
Author(s):  
Nadine Jacques ◽  
Hermann Pettersen ◽  
Kristine Cerbule ◽  
Bent Herrmann ◽  
Ólafur A. Ingólfsson ◽  
...  
Keyword(s):  
Deep Water ◽  
Barents Sea ◽  
Juvenile Fish ◽  
Size Selectivity ◽  
Pandalus Borealis ◽  
Trawl Fishery ◽  
Bycatch Reduction ◽  
Drag Forces ◽  
The Barents Sea ◽  
Trawl Fisheries

In most trawl fisheries, drag forces tend to close the meshes in large areas of diamond mesh codends, negatively affecting their selective potential. In the Barents Sea deep-water shrimp (Pandalus borealis) trawl fishery, selectivity is based on a sorting grid followed by a diamond mesh codend. However, the retention of juvenile fish as well as undersized shrimp is still a problem. In this study, we estimated the effect of applying different codend modifications, each aimed at affecting codend mesh openness and thereby selectivity. Changing from a 4-panel to a 2-panel construction of the codend did not affect size selectivity. Shortening the lastridge ropes of a 4-panel codend by 20% resulted in minor reductions for juvenile fish bycatch, but a 45% reduction of undersized shrimp was observed. Target-size catches of shrimp were nearly unaffected. When the codend mesh circumference was reduced while simultaneously shortening the lastridge ropes, the effect on catch efficiency for shrimp or juvenile fish bycatch was marginal compared to a 4-panel codend design with shortened lastridge ropes.

scholarly journals Bycatch reduction in the deep-water shrimp (Pandalus borealis) trawl fishery with a large mesh top panel

2021 ◽  
pp. 126001
Author(s):  
Kristine Cerbule ◽  
Nadine Jacques ◽  
Hermann Pettersen ◽  
Ólafur A. Ingólfsson ◽  
Bent Herrmann ◽  
...  
Keyword(s):  
Deep Water ◽  
Pandalus Borealis ◽  
Trawl Fishery ◽  
Bycatch Reduction

scholarly journals Potential for codends with shortened lastridge ropes to replace mandated selection devices in demersal trawl fisheries

2021 ◽  
Author(s):  
Manu Sistiaga ◽  
Jesse Brinkhof ◽  
Bent Herrmann ◽  
Roger B. Larsen ◽  
Eduardo Grimaldo ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Size Selectivity ◽  
The Barents Sea ◽  
Alternative Solutions ◽  
Trawl Fisheries

In many trawl fisheries, codend size selectivity is supplemented by adding selection devices to the gear. In the Barents Sea gadoid fishery, combining diamond mesh codends with sorting grids is compulsory. However, the use of grids increases the costs and complexity of the gear, causing discontent among fishermen and prompting researchers to seek alternative solutions. Lastridge ropes are ropes attached to the selvedges of the codend. In this study, we tested the effect of shortening the lastridge ropes of two diamond mesh codends with different mesh sizes on the size selectivity of cod (Gadus morhua), haddock (Melanogramus aeglefinnus), and redfish (Sebastes spp.). Shortening the lastridge ropes by 15% increased the mesh opening during the fishing process, which significantly improved the size-selective properties of the codends. Further, the L50 values were always higher for the codends in the short lastridge configuration. Therefore, codends with shortened lastridge ropes may be a simpler alternative to sorting grids in this fishery, and they may be applicable to many other fisheries in which additional selection devices are used.

scholarly journals Effect of a quality-improving cod end on size selectivity and catch patterns of cod in bottom trawl fishery

2019 ◽  
Vol 76 (11) ◽  
pp. 2110-2120 ◽  
Author(s):  
Jesse Brinkhof ◽  
Bent Herrmann ◽  
Roger B. Larsen ◽  
Tiago Veiga-Malta
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Relative Size ◽  
Bottom Trawl ◽  
Size Selectivity ◽  
Total Size ◽  
Trawl Fishery ◽  
The Barents Sea ◽  
Sea Bottom ◽  
Significant Difference

A new cod-end concept developed and tested exhibited significantly improved quality of caught cod (Gadus morhua) compared with that of the conventional cod end used in the Barents Sea bottom trawl fishery. However, the design of the new quality-improving cod end raised concerns about its size selectivity and the possibility that higher retention probability could negatively impact the catch pattern by increasing the proportion of undersized cod. Therefore, the goal of this study was to quantify and compare the size selectivity and catch pattern for cod when deploying, respectively, the conventional and new quality-improving cod end in the Barents Sea bottom trawl fishery. The new quality-improving cod end had significantly lower relative size selectivity than the conventional cod end, but no significant difference in the catch patterns was detected in the trawl. Further, estimation of the total size selectivity in the trawl revealed that the increased retention of small cod when using the quality-improving cod end was minor. Hence, despite the reduced selectivity, the quality-improving cod end can be used with low risk of retaining small cod.

scholarly journals Effect of three different codend designs on the size selectivity of juvenile cod in the Barents Sea shrimp trawl fishery

2019 ◽  
Vol 219 ◽  
pp. 105337
Author(s):  
Bent Herrmann ◽  
Manu Sistiaga ◽  
Roger B. Larsen ◽  
Jesse Brinkhof
Keyword(s):  
Barents Sea ◽  
Size Selectivity ◽  
Trawl Fishery ◽  
The Barents Sea ◽  
Shrimp Trawl

Understanding limits to cod and haddock separation using size selectivity in a multispecies trawl fishery: an application of FISHSELECT

2011 ◽  
Vol 68 (5) ◽  
pp. 927 ◽  
Author(s):  
Manu Sistiaga ◽  
Bent Herrmann ◽  
Kåre N. Nielsen ◽  
Roger B. Larsen
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Morphological Characteristics ◽  
Melanogrammus Aeglefinus ◽  
Size Selectivity ◽  
Sea Trial ◽  
Trawl Fishery ◽  
The Barents Sea ◽  
Morphological Differences

This investigation demonstrates how a multidisciplinary approach based on the FISHSELECT framework, sea trial data, underwater recordings, and laboratory investigations of netting can be applied to size selectivity studies and related management issues. We studied the morphological characteristics of Atlantic cod ( Gadus morhua ) and haddock ( Melanogrammus aeglefinus ) in the Barents Sea bottom trawl fishery. The differences between the L50 values (i.e., the size at which a fish has a 50% chance of being retained) that were recorded for the two species during sea trials can to a large extent be explained by the morphological differences between them. Because of these morphological differences, L50 is always larger for cod than for haddock with the grid and codend setup commonly used in the area. While catch separation of cod and haddock is a management objective in the Barents Sea, we demonstrate that the morphological differences between the species and the grid and codend setup in force today limit achievable differences in L50 to 5.5 cm. Furthermore, we show that for this fishery, the scope for increasing L50 differences between these species by changing the mesh shape configuration of the codend is minimal.

scholarly journals The genetic structure of Pandalus borealis in the Northeast Atlantic determined by RAPD analysis

2006 ◽  
Vol 63 (5) ◽  
pp. 840-850 ◽  
Author(s):  
Iciar Martinez ◽  
Michaela Aschan ◽  
Taran Skjerdal ◽  
Salah M. Aljanabi
Keyword(s):  
Genetic Structure ◽  
Barents Sea ◽  
Rapd Analysis ◽  
Rapd Marker ◽  
Arbitrary Primers ◽  
Pandalus Borealis ◽  
Northeast Atlantic ◽  
The Barents Sea ◽  
Local Selection ◽  
Significant Difference

Abstract The genetic structure of shrimp (Pandalus borealis) in the Northeast Atlantic was examined by RAPD analysis on specimens caught at eight stations in the Barents Sea, three off Svalbard, two off Jan Mayen, and in two northern Norwegian fjords (19 < n > 31 per station). A total of 34 polymorphic markers generated by seven 10-mer arbitrary primers was used to assess the genetic population structure using analysis of molecular variance (AMOVA). There was considerable RAPD diversity (>90%) among shrimp at all stations. The two Norwegian fjords and the Jan Mayen stations were different from all the others, and the Jan Mayen stations also differed from each other. More than 98% of the genetic variation between Barents Sea and Svalbard was ascribed to individual diversity, and there was no significant difference between the two areas, although there seemed to be a subpopulation structure in the Barents Sea. Principal component analysis on the frequency of each RAPD marker on each sampled station confirmed the presence of three populations: Barents Sea and Svalbard, northern Norwegian fjords, and Jan Mayen. We postulate that the large genetic variability found at an individual level may provide the total population with a diverse genetic pool from which traits can be selected to respond to variations in local environmental conditions, and that this local selection may be the cause of the subpopulation structure observed.

scholarly journals Comparison of shortest sailing distance through random and regular sampling points

2004 ◽  
Vol 61 (1) ◽  
pp. 140-147 ◽  
Author(s):  
Alf Harbitz ◽  
Michael Pennington
Keyword(s):  
Random Sampling ◽  
Minimum Distance ◽  
Barents Sea ◽  
Pandalus Borealis ◽  
The Barents Sea ◽  
Theoretical Sampling ◽  
Sampling Points ◽  
Regular Sampling ◽  
The Mean ◽  
The Difference

Abstract The shortest sailing distance through n sampling points is calculated for simple theoretical sampling domains (square and circle) as well as for a rather irregular and concavely shaped real sampling domain in the Barents Sea. The sampling sites are either located at the nodes of a square grid (regular sampling) or they are randomly distributed. For n less than ten, the exact shortest sailing distance is derived. For larger n, a traveling salesman algorithm (simulated annealing) was applied, and its bias (distance from true minimum) was estimated based on a case where the true minimum distance was known. In general, the average minimum sailing distance based on random sampling was considerably shorter than for regular sampling, and the difference increased with sample size until an asymptotic value was reached at about n=60 for a square domain. For the sampling domain in the Barents Sea used for shrimp (Pandalus borealis) abundance surveys (n=118 stations), the cruise-track lengths based on random sampling were approximately normally distributed. The mean sailing distance was 18% shorter than the cruise track for regular sampling and the standard deviation equalled 2.6%.

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