scholarly journals Out with the old and in with the new: T90 codends improve size selectivity in the Canadian redfish (Sebastes mentella) trawl fishery

2020 ◽  
Vol 77 (10) ◽  
pp. 1711-1720
Author(s):  
Zhaohai Cheng ◽  
Paul D. Winger ◽  
Shannon M. Bayse ◽  
Gebremeskel Eshetu Kebede ◽  
Harold DeLouche ◽  
...  
Keyword(s):  
Size Selectivity ◽  
Size Selection ◽  
Trawl Fishery ◽  
Minimum Landing Size ◽  
Sebastes Mentella

The size selectivity of four codends were compared in the Gulf of St. Lawrence, Canada, redfish fishery (Sebastes mentella), including the regulated diamond mesh codend with a mesh opening of 90 mm (T0) and three experimental codends of different mesh openings (90, 100, 110 mm) in which the netting is turned 90° to the direction of tow (T90). Results for the regulated codend showed that there was little size selection, catching greater than 97% of redfish over all of the length classes observed. Considering the fished population, the smallest T90 codend would catch 30% fewer redfish under the minimum landing size (MLS) of 22 cm compared with the T0 codend, but would also lose 16% of catch above 22 cm. The T90 codend with 100 mm mesh opening had the same size selectivity as the smallest T90 codend. The 110 mm T90 codend would catch 50% less redfish below MLS but lose 40% of redfish above MLS. Overall, results show that T90 codends improve size selectivity in which large proportions of undersized fish are successfully released.

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 Effects of six codend meshes on the size selection of juvenile white croaker (Pennahia argentata) in demersal trawl fishery of the South China Sea

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0253723
Author(s):  
Bingzhong Yang ◽  
Bent Herrmann ◽  
Lei Yan ◽  
Jie Li ◽  
Teng Wang
Keyword(s):  
South China Sea ◽  
South China ◽  
Mesh Size ◽  
The South China Sea ◽  
Size Selectivity ◽  
White Croaker ◽  
Trawl Fishery ◽  
Minimum Landing Size ◽  
Pennahia Argentata ◽  
Selection Of

White croaker (Pennahia argentata) is a commercially important but overexploited species that is often caught in trawl fishery of the South China Sea (SCS). The codend size selectivity for this species in the local commercial trawl fishery is of concern when considering the established minimum landing size (MLS). This study investigated the size selectivity of white croaker for six different diamond-mesh codends with mesh size from 25 to 54 mm. We paid special attention to two codends, made with meshes of 25 and 40 mm in size, which are currently used according to the regulations established in the SCS. The results demonstrated that the legal codends do not perform satisfactorily in the fishing grounds where juvenile white croaker is relatively abundant. This is because at a length similar to the minimum landing size of the species (MLS = 15.0 cm), all white croaker were retained, and the estimated discard ratio was >97% in both cases of legal codends. Our study showed that by increasing the mesh size, the size selection of tested codends could be improved for white croaker, and the retention rates for juvenile fish would decrease. However, none codend was proved efficient to release undersized white croaker suggesting that other gear design changes may be necessary.

scholarly journals Predictive framework for codend size selection of brown shrimp (Crangon crangon) in the North Sea beam-trawl fishery

PLoS ONE ◽  
2018 ◽  
Vol 13 (7) ◽  
pp. e0200464 ◽  
Author(s):  
Juan Santos ◽  
Bent Herrmann ◽  
Daniel Stepputtis ◽  
Claudia Günther ◽  
Bente Limmer ◽  
...  
Keyword(s):  
North Sea ◽  
Brown Shrimp ◽  
Beam Trawl ◽  
Crangon Crangon ◽  
Size Selection ◽  
Trawl Fishery ◽  
The North ◽  
Sea Beam ◽  
The North Sea ◽  
Selection Of

scholarly journals Factors affecting rule compliance with mesh size regulations in the Baltic cod trawl fishery

2007 ◽  
Vol 64 (8) ◽  
pp. 1603-1606 ◽  
Author(s):  
Petri Suuronen ◽  
Vesa Tschernij ◽  
Pekka Jounela ◽  
Daniel Valentinsson ◽  
P-O. Larsson
Keyword(s):  
Gadus Morhua ◽  
Management Practice ◽  
Mesh Size ◽  
Factors Affecting ◽  
Trawl Fishery ◽  
Management Measures ◽  
Gradual Introduction ◽  
Minimum Landing Size ◽  
The Baltic ◽  
Baltic Cod

Abstract Suuronen, P., Tschernij, V., Jounela, P., Valentinsson, D., and Larsson, P-O. 2007. Factors affecting rule compiance with mesh size regulations in the Baltic cod trawl fishery. – ICES Journal of Marine Science, 64: 1603–1606. In this study, we evaluate the efficiency and applicability of a series of gear-based management measures, enforced since 1990, whose purpose was to improve size selectivity in the trawl fishery for Baltic cod (Gadus morhua). In general, our study revealed that these measures had no marked effect on the capture and discard of young cod. Legal and illegal manipulation of selective codends was widespread. The adoption of a codend design that offered a modest increase in selectivity, but had a good match with the legislated minimum landing size (MLS), led to greater compliance, demonstrating that a mismatch between MLS and selectivity should be avoided. It was also obvious that, generally, the fishing industry did not tolerate large short-term losses. Our evaluation is that overly ambitious rules will be circumvented, and frequent and incoherent changes in the regulations represent bad management practice. A gradual introduction of restrictions and participation by fishers in the decision-making process will increase compliance.

scholarly journals Catch pattern and size selectivity for a gear designed to prevent fish injuries during the capture process in a North-East Atlantic demersal trawl fishery

2020 ◽  
Vol 40 ◽  
pp. 101525
Author(s):  
Bent Herrmann ◽  
Manu Sistiaga ◽  
Roger B. Larsen ◽  
Jesse Brinkhof ◽  
Svein Helge Gjøsund ◽  
...  
Keyword(s):  
Size Selectivity ◽  
East Atlantic ◽  
Capture Process ◽  
Trawl Fishery ◽  
North East

Reproductive biology of Polybius henslowii Leach, 1820 (Decapoda, Polybiidae): a discard species from the northwestern Portuguese beam trawl fishery

Crustaceana ◽  
2014 ◽  
Vol 87 (7) ◽  
pp. 784-800 ◽  
Author(s):  
L. Magalhães ◽  
M. Felício ◽  
M. B. Gaspar ◽  
V. Quintino ◽  
A. M. Rodrigues
Keyword(s):  
Reproductive Biology ◽  
Current Knowledge ◽  
Carapace Width ◽  
Fishing Gear ◽  
Northern Coast ◽  
Beam Trawl ◽  
Total Catch ◽  
Important Species ◽  
Trawl Fishery ◽  
Minimum Landing Size

Polybius henslowii Leach, 1820, a Portunid crab distributed from the British Isles to Morocco and the Mediterranean Sea is caught in high densities by many types of fishing gear and frequently thrown back to the sea. Along the northern coast of Portugal, P. henslowii is an important species discarded in beam trawl fishery. There are no quantitative estimations of discards and very little is known about its biology, information that is needed to value this species. The present work was conducted from March 2007 to December 2010 in order to improve the current knowledge of the reproductive biology of P. henslowii. By-catches were registered aboard commercial vessels that volunteered to participate in the study. In that period P. henslowii represented 57.3% of the total catch and was present in all hauls analysed. The target species, Palaemon serratus (Pennant, 1777), represented 1.2% of the total catch, showing the low selectivity of the fishing gear and the need for suppression of this gear to catch this shrimp species. Differences in size between sexes were found, with males being larger and heavier than females. Mature females occurred mainly in autumn and the carapace width at which 50% of the females reach maturity was estimated to be 37.8 mm, which could be set as the minimum landing size of this potential exploitable resource. A macroscopic ovarian maturity stages classification was proposed, allowing a rapid field assessment of female sexual maturity. This study fills a gap in the knowledge of a very important species discarded in beam trawl fishery that may be basis of further work.

Grid selection in the North Sea industrial trawl fishery for Norway pout: Efficient size selection reduces bycatch

2006 ◽  
Vol 77 (2) ◽  
pp. 248-263 ◽  
Author(s):  
Kurt Kvalsvik ◽  
Ingvar Huse ◽  
Ole Arve Misund ◽  
Kjell Gamst
Keyword(s):  
North Sea ◽  
Size Selection ◽  
Trawl Fishery ◽  
The North ◽  
The North Sea ◽  
Grid Selection

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.

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