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 The vertical separation of fish in the aft end of a demersal trawl

2009 ◽  
Vol 66 (4) ◽  
pp. 772-777 ◽  
Author(s):  
Ludvig Ahm Krag ◽  
René Holst ◽  
Niels Madsen
Keyword(s):  
Vertical Distribution ◽  
Gadus Morhua ◽  
Melanogrammus Aeglefinus ◽  
Multinomial Model ◽  
Vertical Separation ◽  
Commercially Important ◽  
Merlangius Merlangus ◽  
The Vertical Distribution ◽  
Haddock Melanogrammus Aeglefinus ◽  
Important Fish

Abstract Krag, L. A., Holst, R., and Madsen, N. 2009. The vertical separation of fish in the aft end of a demersal trawl. – ICES Journal of Marine Science, 66: 772–777. Two multi-compartment separator frames were used to study the vertical separation of some commercially important fish species in the aft end of a trawl, with the aim of separating cod (Gadus morhua) from other species. A non-linear multinomial model with random effects was used to analyse the data and to compare the performance of the two frames. The vertical distribution of cod in the aft end of the trawl was close to uniform, whereas haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), plaice (Pleuronectes platessa), and lemon sole (Microstomus kitt) showed more uneven distributions. The use of guiding bars in the separator frame significantly (p < 0.05) increased the catch of cod, plaice, and lemon sole in the upper compartment. The vertical separation of cod was density-dependent; high densities of fish resulted in a more uniform distribution of cod. The species separations found differ from those reported from the studies of species separation in the region of the trawl mouth.

scholarly journals The effect of Nordmøre grid length and angle on codend entry of bycatch fish species and shrimp catches

2019 ◽  
Vol 76 (2) ◽  
pp. 308-319 ◽  
Author(s):  
Roger B. Larsen ◽  
Manu Sistiaga ◽  
Bent Herrmann ◽  
Jesse Brinkhof ◽  
Ivan Tatone ◽  
...  
Keyword(s):  
Fish Species ◽  
Gadus Morhua ◽  
Melanogrammus Aeglefinus ◽  
Northern Shrimp ◽  
Shrimp Trawl ◽  
Fisheries Bycatch ◽  
Shrimp Fisheries ◽  
Trawl Fisheries ◽  
Grid Length ◽  
Haddock Melanogrammus Aeglefinus

The Nordmøre grid is regarded as an efficient bycatch-reducing device and is used in various shrimp trawl fisheries globally. However, in some shrimp fisheries, bycatch remains a problem that seriously impacts commercial trawl activities. This study tested and compared the performance of two versions of the Nordmøre grid in the northeast Arctic deepwater (northern) shrimp (Pandalus borealis) fishery, a standard version with an operating angle of approximately 45° and a longer version of the grid (40% longer) with an operating angle of approximately 30°. The grid passage probability for the bycatch of juvenile cod (Gadus morhua), haddock (Melanogrammus aeglefinus), American plaice (Hippoglossoides platessoides), and redfish (Sebastes spp.) increased significantly for certain size ranges of fish when using the longer grid. The longer grid also resulted in a significant increase in grid passage probability for large shrimp. Previous studies have reported that a reduced operating angle can lead to a lower grid passage probability for bycatch fish species and shrimp; however, the results of the current study demonstrate that a longer Nordmøre grid more than compensates for the reduced operational angle.

scholarly journals Trawl hangs, baby fish, and closed areas: a win–win scenario

2003 ◽  
Vol 60 (5) ◽  
pp. 930-938 ◽  
Author(s):  
Jason S Link ◽  
Chad Demarest
Keyword(s):  
Gadus Morhua ◽  
Juvenile Fish ◽  
Melanogrammus Aeglefinus ◽  
Minimal Distance ◽  
Range Of Movement ◽  
Naturally Occurring ◽  
Sea Raven ◽  
High Concentrations ◽  
Degree Of Association ◽  
Hemitripterus Americanus

Abstract The frequency and geographic distribution of trawlnet hangs from a fishery-independent survey are evaluated. The hangs data were plotted on a substratum map to confirm that many, but not all, were naturally occurring, high relief substrata. The data were also coupled with the occurrence of juvenile cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) to assess the degree of association between juvenile gadoids and high relief substrata. The average minimal distance from a fish occurrence to a hang ranged from 8.1 to 12.0 km (4.4–6.5 nautical miles), well within the reported daily range of movement for these fish. A similar pattern was detected for the sea raven (Hemitripterus americanus), a predator of juvenile gadoids, confirming the location of these microhabitat foodwebs. On average, closing an area 3.7 km (2 nautical miles) around a hang will enclose 17–30% of the populations of these juvenile fish; a wider buffer (18–28 km; 10–15 nautical miles) will close a linearly increasing portion of the populations. Additionally, closing areas surrounding the hangs, particularly regions of high hang density, will help to minimize losses of or damage to fishing gear. We propose a win–win scenario by establishing or evaluating closed areas in regions with high concentrations of known hangs. This approach is widely applicable for many marine ecosystems and may help to achieve simultaneous conservation and resource management goals, whereby one can both protect pre-recruit fish and enhance the effectiveness of a fishery.

scholarly journals FLEXSELECT: counter-herding device to reduce bycatch in crustacean trawl fisheries

2018 ◽  
Vol 75 (6) ◽  
pp. 850-860 ◽  
Author(s):  
Valentina Melli ◽  
Junita D. Karlsen ◽  
Jordan P. Feekings ◽  
Bent Herrmann ◽  
Ludvig A. Krag
Keyword(s):  
Gadus Morhua ◽  
Melanogrammus Aeglefinus ◽  
Target Species ◽  
Merluccius Merluccius ◽  
Flexible Tool ◽  
Flatfish Species ◽  
Trawl Fishery ◽  
Merlangius Merlangus ◽  
Trawl Fisheries ◽  
Haddock Melanogrammus Aeglefinus

FLEXSELECT is a simple counter-herding device that aims at reducing the bycatch of fish by scaring them away from the trawl path without affecting the catches of the target species. FLEXSELECT was tested in the Norway lobster (Nephrops norvegicus) directed trawl fishery, as this includes bycatch of both roundfish and flatfish. Length-based data were collected for Nephrops, four roundfish species (cod (Gadus morhua), haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and hake (Merluccius merluccius)), and two flatfish species (plaice (Pleuronectes platessa) and lemon sole (Microstomus kitt)), and length-based catch comparisons were performed. No significant effect on the target species, Nephrops, was detected, whereas a reduction of 39% (CI: 29%–46%) was obtained for the overall number of fish. Catches of all the six fish species examined were significantly reduced by FLEXSELECT, with the efficiency varying considerably among species and over length classes. No significant diel differences were found for either roundfish or flatfish species. FLEXSELECT prevents bycatch species from interacting with the trawl, thus most likely enhancing their survival and fitness. Moreover, its fast attachment system makes FLEXSELECT a flexible tool, adaptable to different fisheries and catch goals.

scholarly journals Feeding habits of harp and hooded seals in Greenland waters

2000 ◽  
Vol 2 ◽  
pp. 50 ◽  
Author(s):  
Finn O Kapel
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Minor Role ◽  
Published Data ◽  
Polar Cod ◽  
Small Fish ◽  
Greenland Halibut ◽  
Important Prey

Results of stomach contents analyses of harp and hooded seals collected in West Greenland waters in the period 1986-1993 are reviewed, and compared with published data and circumstantial information from local hunters. The diet of harp seals in this region is variable but consists mainly of pelagic crustaceans (Thysanoessa spp. and Parathemisto libellula) and small fish species like capelin (Mallotus villosus), sandeel (Ammodytes spp.), polar cod (Boreogadus saida) and Arctic cod (Arctogadus glacialis). Species of importance for commercial fisheries in Greenland, such as Northern prawn (Pandalus borealis), Atlantic cod (Gadus morhua), and Greenland halibut (Reinhardtius hippoglossoides) play a minor role in the diet of harp seals in this area.Variation in the diet of hooded seals is less well documented, but in addition to the species also taken by harp seals, larger demersal fishes like Greenland halibut, redfish (Sebastes spp.), cod, and wolffish (Anarhichas minor) are apparently important prey items.

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.

Parasites as biological tags in marine fisheries research: European Atlantic waters

Parasitology ◽  
2014 ◽  
Vol 142 (1) ◽  
pp. 54-67 ◽  
Author(s):  
K. MACKENZIE ◽  
W. HEMMINGSEN
Keyword(s):  
Marine Mammals ◽  
Gadus Morhua ◽  
Clupea Harengus ◽  
Melanogrammus Aeglefinus ◽  
Ecological Group ◽  
The North ◽  
Recent Developments ◽  
Host Parasite ◽  
Mediterranean And Black Seas ◽  
Biological Tags

SUMMARYStudies of the use of parasites as biological tags for stock identification and to follow migrations of marine fish, mammals and invertebrates in European Atlantic waters are critically reviewed and evaluated. The region covered includes the North, Baltic, Barents and White Seas plus Icelandic waters, but excludes the Mediterranean and Black Seas. Each fish species or ecological group of species is treated separately. More parasite tag studies have been carried out on Atlantic herring Clupea harengus than on any other species, while cod Gadus morhua have also been the subject of many studies. Other species that have been the subjects of more than one study are: blue whiting Micromesistius poutassou, whiting Merlangius merlangus, haddock Melanogrammus aeglefinus, Norway pout Trisopterus esmarkii, horse mackerel Trachurus trachurus and mackerel Scomber scombrus. Other species are dealt with under the general headings redfishes, flatfish, tunas, anadromous fish, elasmobranchs, marine mammals and invertebrates. A final section highlights how parasites can be, and have been, misused as biological tags, and how this can be avoided. It also reviews recent developments in methodology and parasite genetics, considers the potential effects of climate change on the distributions of both hosts and parasites, and suggests host-parasite systems that should reward further research.

scholarly journals Development of Atlantic cod (Gadus morhua) exposed to produced water during early life stages: Effects on embryos, larvae, and juvenile fish

2010 ◽  
Vol 70 (5) ◽  
pp. 383-394 ◽  
Author(s):  
Sonnich Meier ◽  
H. Craig Morton ◽  
Gunnar Nyhammer ◽  
Bjørn Einar Grøsvik ◽  
Valeri Makhotin ◽  
...  
Keyword(s):  
Early Life ◽  
Gadus Morhua ◽  
Produced Water ◽  
Atlantic Cod ◽  
Juvenile Fish ◽  
Life Stages ◽  
Early Life Stages

scholarly journals Population dynamics of two sympatric intertidal fish species (the shanny, Lipophrys pholis and long-spined scorpion fish, Taurulus bubalis) of Great Britain

2016 ◽  
Vol 98 (3) ◽  
pp. 589-595 ◽  
Author(s):  
C.J. Barrett ◽  
M.L. Johnson ◽  
S.L. Hull
Keyword(s):  
Population Dynamics ◽  
Great Britain ◽  
Fish Species ◽  
Gadus Morhua ◽  
Sympatric Species ◽  
Rocky Intertidal ◽  
Melanogrammus Aeglefinus ◽  
Intertidal Zones ◽  
Spatio Temporal ◽  
Scorpion Fish

The shanny/common blenny (Lipophrys pholis) and long-spined scorpionfish/bullhead (Taurulus bubalis) are commonly encountered, sympatric species within much of Great Britain's rocky intertidal zones. Despite being prey items of the cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) respectively, and both contributors to the diet of the near-threatened European otter (Lutra lutra), little is known on the population dynamics of the temperate specimens of Great Britain. It is further less known of the degrees of sympatricity between the two fish species and to what extent they are able to coexist. The current study examines spatio-temporal distributions and abundances at various resolutions: monthly population dynamics of both species along England's Yorkshire coast and seasonal population dynamics along the Yorkshire coast and around the Isle of Anglesey, Wales. Studies of their abundances, sizes, degrees of rock pool co-occurrence and diel activities are further examined, which indicate coexistence is maintained when interspecific co-occurrence takes place only between specimens of similar sizes, thus demoting size-related dominance hierarchies.

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