scholarly journals Size selectivity and length-dependent escape behaviour of haddock in a sorting device combining a grid and a square mesh panel

2019 ◽  
Vol 76 (8) ◽  
pp. 1350-1361 ◽  
Author(s):  
Bent Herrmann ◽  
Manu Sistiaga ◽  
Eduardo Grimaldo ◽  
Roger B. Larsen ◽  
Leonore Olsen ◽  
...  
Keyword(s):  
Barents Sea ◽  
Selection Process ◽  
Species Selection ◽  
Melanogrammus Aeglefinus ◽  
Size Selectivity ◽  
Escape Behaviour ◽  
Trawl Fishery ◽  
Haddock Melanogrammus Aeglefinus ◽  
Better Than ◽  
Modelling Approach

Size selectivity of a new sorting section combining a sorting grid and a square mesh panel was tested for haddock (Melanogrammus aeglefinus) in the Barents Sea demersal trawl fishery. Sampling data for a wide size range enabled investigating the selection process for this species in detail, both for the grid and the square mesh panel. Contrary to earlier studies modelling size selectivity for grids and square mesh panels, which assume that the escape behaviour of all sizes of fish is equal, we applied a model that accounted for haddock of different sizes showing different escape behaviours. Our results demonstrated that this model could describe the experimental data collected better than existing models. Specifically, our results showed that the likelihood for smaller haddock to seek escape through the grid and the square mesh panel was higher than that for bigger haddock that still would manage to escape through the devices if they attempted. The new modelling approach presented in this study may be applicable to other species, selection devices, and fisheries.

scholarly journals Improving release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) in the Barents Sea demersal trawl fishery by stimulating escape behaviour

2018 ◽  
Vol 75 (3) ◽  
pp. 402-416 ◽  
Author(s):  
Eduardo Grimaldo ◽  
Manu Sistiaga ◽  
Bent Herrmann ◽  
Roger B. Larsen ◽  
Jesse Brinkhof ◽  
...  
Keyword(s):  
Mechanical Stimulation ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Melanogrammus Aeglefinus ◽  
Light Stimulation ◽  
Escape Behaviour ◽  
Led Light ◽  
Trawl Fishery ◽  
Size Limits ◽  
Haddock Melanogrammus Aeglefinus

We tested the ability of stimulators to improve the release efficiency of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) through the meshes of a square mesh section installed in a trawl. The section was tested in three different configurations: without any stimulation device, with a mechanical stimulation device, and with LED light stimulation devices. We analysed and compared the behaviour of cod and haddock in all three configurations based on release results and underwater recordings. Parallel to the fishing trials, we carried out fall-through tests to determine the upper physical size limits for cod and haddock to be able to escape through the square meshes in the section. This enabled us to infer whether lack of release efficiency was due to fish behaviour or release potential of the square meshes in the section. The results showed that the escape behaviour of haddock can be triggered by mechanical stimulation. In contrast, cod did not react significantly to the presence of mechanical stimulators. LED light stimulation had some effect on the behaviour of haddock, but not on cod.

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 Assessment of size selectivity in hydraulic clam dredge fisheries

2017 ◽  
Vol 74 (3) ◽  
pp. 339-348 ◽  
Author(s):  
Antonello Sala ◽  
Jure Brčić ◽  
Bent Herrmann ◽  
Alessandro Lucchetti ◽  
Massimo Virgili
Keyword(s):  
Data Analysis ◽  
Field Study ◽  
Fishery Management ◽  
Selection Process ◽  
Hole Diameter ◽  
Knife Edge ◽  
Size Selectivity ◽  
Benthic Species ◽  
Size Selection ◽  
Modelling Approach

In hydraulic dredge clam fisheries, the onboard mechanical sorting can be considered as the main catch selection process. The catch is mechanically sorted by a sieve made up of a series of successive grids with holes of decreasing diameter. The effect of the grid hole diameter and sorting speed of the vibrating sieve of a hydraulic dredger was investigated in a field study to determine its clam selection properties and to formulate proposals aimed at improving fishery management. Data analysis demonstrates that it is technically impossible to achieve a knife-edge selection and that there is scope for improving the size selection process, for instance by increasing grid hole diameter, which, however, can be accompanied by a reduced catch of both undersized and commercial-sized individuals. An increase in the hole diameter to 21.71 mm, while ensuring less than 5% retention of undersized individuals, would entail a retention of 67% of the commercial sizes. The modelling approach applied can be extended to investigations of other dredge gear types and nonmobile benthic species.

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 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
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