scholarly journals New approach for modelling size selectivity in shrimp trawl fisheries

2017 ◽  
Vol 75 (1) ◽  
pp. 351-360 ◽  
Author(s):  
Roger B Larsen ◽  
Bent Herrmann ◽  
Manu Sistiaga ◽  
Jesse Brinkhof ◽  
Ivan Tatone ◽  
...  
Keyword(s):  
Barents Sea ◽  
Cold Water ◽  
Small Fish ◽  
Size Selectivity ◽  
Size Selection ◽  
Trawl Fishery ◽  
Size Dependent ◽  
Shrimp Trawl ◽  
Pass Through ◽  
The Individual

Abstract In the deep sea trawl fishery targeting shrimp (Pandalus borealis) and other cold-water shrimp species, fishers often use a Nordmöre sorting grid ahead of a small mesh codend to avoid bycatch. However, small fish can pass through the grid and are subsequently retained in the codend. This makes shrimp size selection complex and the size-dependent curve for both the shrimp and the bycatch species often exhibits a bell-shaped signature. In this study we developed a new model and method to estimate size selection in this fishery, conducted fishing trials in the Northeast Barents Sea, and applied the new method to quantify the individual and combined size selection of the Nordmöre grid and codend for deep water shrimp and two bycatch species. The size selectivity for both bycatch species showed the expected bell-shaped signature with low retention probability of very small and larger fish. The Nordmöre grid had high passage probability for all sizes, although it decreased slightly for the largest shrimps. The smallest shrimps were released by the codend.

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

Using electronic monitoring to record catches of sole (Solea solea) in a bottom trawl fishery

2017 ◽  
Vol 74 (5) ◽  
pp. 1421-1427 ◽  
Author(s):  
Aloysius T. M. van Helmond ◽  
Chun Chen ◽  
Jan Jaap Poos
Keyword(s):  
Electronic Monitoring ◽  
Single Species ◽  
Small Fish ◽  
Trawl Fishery ◽  
Video Review ◽  
Video Observations ◽  
Solea Solea ◽  
Simple Protocol ◽  
Absolute Agreement ◽  
The Individual

Electronic monitoring (EM) is often presented as a solution to document all catches through video observations under the EU landing obligation. However, identifying small fish on video in large volumes of catch is challenging. In this study, logbook records were compared with video observations for catches to test efficacy of EM for different size classes of sole (Solea solea) on board bottom trawlers. Comparisons were based on: (i) systematic differences (paired t-test), (ii) linear correlation (Pearson’s r), and (iii) absolute agreement (ICC). Results suggest that EM of small individuals in mixed fisheries is not as effective as it is for large individuals. To improve efficiency for estimating quantities of small fish, additional methods are required to enhance video review. One possible method for enhancing video review is using a protocol where crew arranged the individual fish in front of the cameras. Indeed, this study suggests that such a protocol substantially improves EM of the complete catch. However, the protocol requires an additional three minutes of processing time per haul for a single species. Given the large number of quota species under the landing obligation for this fishery, implementing the protocol thus comes with a cost for the fishing industry; the extra time needed to conduct a simple protocol probably would exceed 12 h per fishing trip.

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 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 Can vertical separation of species in trawls be utilized to reduce bycatch in shrimp fisheries?

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0249172
Author(s):  
Roger B. Larsen ◽  
Bent Herrmann ◽  
Jure Brčić ◽  
Manu Sistiaga ◽  
Kristine Cerbule ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Juvenile Fish ◽  
Melanogrammus Aeglefinus ◽  
Polar Cod ◽  
Small Fish ◽  
Vertical Separation ◽  
Shrimp Trawl ◽  
Pass Through ◽  
Trawl Fisheries ◽  
The Vertical Distribution

Several shrimp trawl fisheries use a Nordmöre sorting grid to avoid bycatch of fish. However, small fish can pass through the grid. Therefore, the retention of juvenile fish often remains an issue during shrimp trawling. We investigated the vertical distribution of deepwater shrimp (Pandalus borealis) and dominant bycatch species at the point where the Nordmöre grid section is installed. This was achieved using a separator frame which split the net vertically into three compartments of equal entry size. Our results showed that shrimp predominately follow the lower part of the trawl belly, whereas species such as redfish (Sebastes spp.), cod (Gadus morhua), polar cod (Boreogadus saida) and American plaice (Hippoglossoides platessoides) preferred the mid-section in the aft of the trawl. Haddock (Melanogrammus aeglefinus) primarily entered through the upper section of the trawl belly. Using these results, we predict that a vertical separation device installed forward of a 19 mm Nordmöre grid combined with a 35 mm codend would result in a significant reduction in bycatch with only minor loss of shrimp.

scholarly journals Escape rate for cod (Gadus morhua) from the codend during buffer towing

2017 ◽  
Vol 75 (2) ◽  
pp. 805-813 ◽  
Author(s):  
Jesse Brinkhof ◽  
Bent Herrmann ◽  
Roger B Larsen ◽  
Manu Sistiaga
Keyword(s):  
Gadus Morhua ◽  
Disease Susceptibility ◽  
Barents Sea ◽  
Escape Rate ◽  
Commercial Fishing ◽  
Size Selectivity ◽  
Size Selection ◽  
Selection For ◽  
Significant Size ◽  
Growth And Reproduction

Abstract The high abundances of Northeast Arctic cod (Gadus morhua) in the Barents Sea have led to the development of a new fishing tactic called buffer towing. On factory trawlers, the trawl is deployed immediately after taking the catch onboard, a tactic used to ensure a continuous supply of fish is being processed. If the desired amount of fish is caught before the catch from the previous haul has been fully processed, the trawl is lifted off the seabed and towed at a given depth at low speed. This is called buffer towing. Cod that escape from the codend when the trawl is shallower than the initial fishing depth are exposed to an increased likelihood of barotrauma-related injuries, increased disease susceptibility, and predation, which could be lethal, or affect growth and reproduction capability. Therefore, this study quantified the escape rate and size selectivity during buffer towing of cod. A new analytical method was applied that allows using the same trawl configuration as applied during commercial fishing and avoids potential bias in the assessment of buffer towing size selection. Our results demonstrated a significant size selection for cod during buffer towing where cod measuring up to at least 42 cm in length were proven to escape. In particular, at least 60% of cod measuring 20 cm were estimated to escape during buffer towing. For cod measuring 30 and 40 cm, at least 53 and 45% were estimated to escape during buffer towing, respectively.

Sign in / Sign up

Export Citation Format

Share Document