A catch comparison study on different codend designs to evaluate bycatch reduction in the North-East Atlantic deep-water shrimp (Pandalus borealis) fishery

Currently, there is a growing interest in the North-East Atlantic deep-water shrimp (Pandalus borealis) fishery with more actors expected to take part in the coming years. As the species and size of targeted shrimp varies globally, selectivity in this fishery is based on a grid system in front of a small mesh sized codend to avoid bycatch while simultaneously maintaining shrimp catches. However, small fish can still pass through the grid and risk being retained in the codend. Thus, the aim of this study was to analyze the selectivity of a modified shrimp trawl codend using shortened lastridges, an increased mesh size and a four panel codend in combination with the Nordmøre grid with the aim of reducing bycatch while simultaneously maintaining the retention of shrimp. This was carried out using a catch comparison analysis between the different treatment codends versus the compulsory two panel, 35 mm diamond mesh codend used in the fishery today. We found that applying shortened lastridge ropes, along with a four panel codend significantly improved the exclusion of redfish at approximately 50 % in length groups below 7.5 cm while simultaneously maintaining shrimp catches. However, a significant increase in catch efficiency for the Greenland halibut occurred. When all treatments were applied, a significant reduction in shrimp was observed as well as a significant reduction in both redfish and Greenland halibut. An additional experiment was undertaken observing the effect of shortened lastridge ropes while the baseline codends used were configured with four panels rather than two. This caused a significant reduction in shrimp as well as redfish and Greenland halibut in the treatment codend. The results from this thesis demonstrates that applying 30% shortened lastridge ropes along with a four panel codend may be a potential solution for the industry in reducing bycatch, but further exploration regarding the exclusion of flatfishes is needed. Reducing the percentage of lastridge shortening may offer some more clarity for these species’

The effect of grid size on catch efficiency and by-catch in the demersal trawl fishery for Norway pout (Trisopterus esmarkii)

Norway pout (Trisopterus esmarkii) is caught with large trawls with small meshed codends, inevitably causing the fishery to have large by-catch issues. To reduce the amount of by-catch, a rigid sorting grid was made compulsory in 2010. However, there is still a severe by-catch issue, as well as the loss of target species because of the grid. A possible cause might be clogging of the grid, which could be solved by increasing the grid area. Therefore, this study compared the size selectivity of by-catch species and target species in a double-trawl configuration in which one trawl was equipped with a standard grid (6.30 m2), and the other trawl was equipped with a grid that had a 50% larger surface area (9.45 m2). The results demonstrated that the size selectivity and catch efficiency of the target species were unaffected; neither was there any significant difference between the two grids in terms of wanted by-catch species [blue whiting (Micromesistius poutassou), horse mackerel (Trachurus trachurus), and greater argentine (Argentina silus)]. However, the larger grid caught significantly more unwanted by-catch species [haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and hake (Merluccius merluccius)]. Approximately one-third of the accumulated catches comprised the target species, one-third of wanted by-catch species, and one-third of unwanted by-catch species, demonstrating the by-catch challenges in this fishery. Simultaneously, none of the by-catch limits were exceeded.publishedVersio

Improved bycatch reduction in the mixed demersal trawl fishery for Norway pout (Trisopterus esmarkii)

In this study, we compared the bycatch reduction capacity of a trawl fitted with a standard rigid sorting grid with that of a trawl fitted with a newly developed, flexible system called the Excluder. We conducted the fishing trials in the Norway pout (Trisopterus esmarkii) small-meshed trawl fishery in the North Sea. Catch data were analysed by species and length using the catch comparison and catch ratio method. The Excluder significantly reduced the bycatch (in weight) relative to the standard grid for blue whiting (Micromesistius poutassou) (−35.6%), mackerel (Scomber scombrus) (−93.3%), horse mackerel (Trachurus trachurus) (−99.3%), herring (Clupea harengus) (−89.9%), haddock (Melanogrammus aeglefinus), (−98.6%), whiting (Merlangius merlangus) (−99.3%), cod (Gadus morhua) (−97.1%), European hake (Merluccius merluccius) (−98.0%), and greater argentine (Argentina sphyraena) (−24.5%). For Norway pout there was a marginal decrease in the overall catch efficiency of −1.4%. The observed bycatch reduction efficiency is explained by the larger sorting area of the Excluder relative to the grid's area and by the differences in behaviour between Norway pout and the bycatch species. While it contributes to reduce bycatch of quota regulated species, the Excluder also can potentially affect the profitability of the fishery

Fangstkontroll i kolmulefisket — M/S Morten Einar, mars 2023

Prosjektet fokuserer på å utarbeide tekniske innretninger for å redusere faren for sprenging av trålposer i fisket etter kolmule. Fisket etter kolmule med norske fartøy foregår i all hovedsak med pelagisk trål og i størst grad i havområdene vest av Irland og videre opp i færøysk sone. Fiskeposen utsettes ofte for stor belastning som følge av store fangster. Den største belastningen inntreffer når posen er full når den kommer opp til havoverflaten. Årsaken til dette er de store trykkendringene som gjør at fisken får luft i svømmeblæren og volumet av fisk i fiskeposen øker og krever mere plass. Er det da for lite plass til å kunne kompensere for volumøkningen så kan fiskeposen sprekke (sprenges). Konsekvensen av dette er tap av fangst og ødelagt fiskepose. Prosjektet startet opp i 2018 med møter med næringen om problemstillingene i dette fiskeriet. Havforskningsinstituttet har det faglige ansvaret for prosjektet. I 2019 ble det fulgt opp med praktiske fiskeforsøk og logging av trålposer i fiske ved hjelp av sensorer som ble montert på trålen til seks kolmuletrålere. På grunn av koronasituasjonen ble det ikke gjennomført forsøk som planlagt i 2020, slik at det første organiserte fiskeforsøket i prosjektet ble gjennomført i mars 2021. Det som ble testet da gav oss et godt bilde av hva en burde utvikle videre for å imøtekomme ovennevnte problemstillinger. For videre forsøk i 2022 tok vi med oss erfaringene fra 2021, og kom fram til et konsept som ut fra forsøkene kan være en god løsning for videre praktisk uttesting i kommersielt fiske. Konseptet er et fangstbegrensningssystem som fungerer slik at overskuddsfangst slippes ut av trålen på fiskedypet gjennom stor åpning i trålens underpanel. Fisken som er kommet inn i fiskeposen holdes tilbake ved hjelp av et fiskelås som hindrer utslipp av fisk fra fiskeposen i havoverflaten. Størrelsen på fangstene reguleres ved å binde over fiskeposen slik at den tar ønsket mengde fisk.Fangstkontroll i kolmulefisket — M/S Morten Einar, mars 2023publishedVersio

Catch Control in the Blue Whiting Pelagic Trawl Fishery - Research Cruise Report [2022825]: FV “Vikingbank”

This cruise has demonstrated that the catch limitation system can successfully limit catches in the blue whiting pelagic trawl fishery, with negligible loss during the fishing operation while effectively releasing excessive fish when the codend is full (sections 3 & 6),. This solution can significantly reduce the risk of burst codends and discarding of excess fish, thereby making the blue whiting fishery more sustainable and potentially more profitable, through appropriate certification. However, further work is needed on an effective fish lock design (section 4) and a bycatch release system that does not release excessive target catch (section 6). The depth triggered releasers for reliable release of the codend choker also require further development and testing, which should include defining the optimal release depth (sections 5 & 9). In addition to catch limitation, this cruise also investigated the potential risk to the safety of the vessel and crew, during haul-back and pumping, by estimating the weight in water of the catch with total loss of swimbladder gas buoyancy (section 10). Also tested was a prototype method to mitigate this risk during pumping, by automating the release of the pump by a depth triggered releaser (section 7).Catch Control in the Blue Whiting Pelagic Trawl Fishery - Research Cruise Report [2022825]: FV “Vikingbank”publishedVersio

A catch limitation device to avoid excessive catches in the blue whiting (Micromesistius poutassou) Northeast Atlantic pelagic trawl fishery

Blue whiting (Micromesistius poutassou) is harvested in the Northeast Atlantic by a multinational fleet of pelagic trawlers. Occasionally, vessels take catches which exceed their remaining holding capacity and in extreme cases large catches cause codends to burst, resulting in spill of catch. To control catch quantity, a catch limitation system was developed and tested. The system consists of three components: 1) escape opening(s) in front of the codend to release excess fish, 2) a fish lock to prevent loss of fish through the escape opening(s) during haulback and at the surface, and 3) a choking unit to match codend capacity to the desired size of catch. Blue whiting escaped through both longitudinal slots and large (≥ 2 m) meshes in front of the codend. However, video observations showed that with large meshes in the upper panel, large amounts of blue whiting escaped long before the codend was full. Therefore, a design with large openings in the bottom was combined with longitudinal slots in the side and top panels. Two fish locks were tested: an oblique netting panel designed to seal off the codend when vessel speed reduce during haulback, and a cylinder of netting with a choking rope that closed it after the codend was filled. Both fish lock designs inhibited release of fish during haulback and at the surface, but the attachment of the constricting rope in the cylinder frequently broke. The choking unit consisted of a depth triggered releaser connected to a strap of rope wrapped around the codend. Mechanical releasers with factory-set depth trigger and electronic versions were tested. Both freed the choke point as intended, but occasionally at unpredictable depth. A reliable relationship (r2 = 0.94) was attained between codend choking position and catch amount, demonstrating that codend capacity could be adjusted to achieve target catch quantities. Our work shows that controlling catch quantity in the blue whiting pelagic trawl fishery can be achieved effectively through relatively simple modifications to the codend section Future work is needed to optimize the fish lock design and ensure the codend choking rope releasers trigger reliably and at the proper depth.A catch limitation device to avoid excessive catches in the blue whiting (Micromesistius poutassou) Northeast Atlantic pelagic trawl fisherypublishedVersio

Pilot project for the short-time live storage of bluefin tuna — Trials onboard MS Vestbris 2023

Norway was historically a major bluefin tuna (BFT) harvesting country. However, fishing for this species has experienced low profitability. One potential solution is short-term live-storage so that the market can be supplied on demand. Further, storing BFT allows a more controlled slaughtering of the fish, resulting in better quality and fish welfare. A pilot project was established in 2020 to address knowledge gaps related to BFT live-storage in Norway. This document summarizes the findings from sea trials in 2023.Pilot project for the short-time live storage of bluefin tuna — Trials onboard MS Vestbris 2023publishedVersio

Pilot project for the short-time live storage of bluefin tuna — Trials onboard MS Vestbris 2023

Norway was historically a major bluefin tuna (BFT) harvesting country. However, fishing for this species has experienced low profitability. One potential solution is short-term live-storage so that the market can be supplied on demand. Further, storing BFT allows a more controlled slaughtering of the fish, resulting in better quality and fish welfare. A pilot project was established in 2020 to address knowledge gaps related to BFT live-storage in Norway. This document summarizes the findings from sea trials in 2023.Pilot project for the short-time live storage of bluefin tuna — Trials onboard MS Vestbris 2023publishedVersio

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

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.acceptedVersio

Specific binding of a hexanucleotide to HIV-1 reverse transcriptase: a novel class of bioactive molecules

Short oligonucleotides below 8–10 nt in length adopt relatively simple structures. Accordingly, they represent interesting and so far unexplored lead compounds as molecular tools and, potentially, for drug development as a rational improvement of efficacy seem to be less complex than for other classes of longer oligomeric nucleic acid. As a ‘proof of concept’, we describe the highly specific binding of the hexanucleotide UCGUGU (Hex-S3) to human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) as a model target. Ultraviolet (UV) cross-linking studies and competition experiments with primer/template substrates and a RT-directed aptamer suggest site-specific binding of Hex-S3 to the large subunit (p66) of the viral enzyme. The affinity of 5.3 μM is related to hexanucleotide-specific suppression of HIV-1 replication in human cells by up to three orders of magnitude indicating that Hex-S3 exerts specific and biologically relevant activity. Experimental evidence described here further suggests a systematic hexamer array-based search for new tools for molecular biology and novel lead compounds in nucleic acid-based drug development