Svein Løkkeborg’s research while affiliated with Institute of Marine Research in Norway and other places

The Norwegian quota for Atlantic bluefin tuna (ABT) (Thunnus thynnus) is not completely caught every year. This is paradoxical because Norway is a leading fishing nation. The fishery is currently executed by rod-and-reel and purse seine, with ∼ 80 % of the quota being allocated to the latter. Purse seine is therefore the main determinant for the overall success of the fishery and vessels aim to take catches that are manageable for their size (typical LOA < 40 m). These vessels are not designed to target ABT, so they tend to have variable capture efficiency, inadequate catch control technology and often produce inconsistent product quality of relatively low value. Furthermore, participation in more profitable fisheries with better shore-based infrastructure and marketing channels is prioritised over ABT fishing. The storage of purse seine caught ABT in cages is currently practiced worldwide but not in Norway. Storage allows on-demand supply to the market and can improve quality by allowing physiological recovery after capture. There is therefore great interest from Norwegian policymakers and industry in developing a live storage fishery. This manuscript investigates aspects related to ABT live storage in Norway. Findings are presented from sea trials exploring the feasibility of these procedures. Challenges that will determine the future perspective of Norwegian live storage are discussed, and the potential of alternatives such as longlines, traps and rod-and-reel is examined. Any future success in developing the Norwegian ABT fishery will serve as an example for other fisheries around the world facing similar challenges.

Red king crab (Paralithodes camtschaticus) represent a valuable inshore fisheries resource for communities in northern Norway. The fishery is regulated east of the 26th meridian by vessel quotas and a minimum landing size of 130 mm carapace length. It is executed using baited pots that must be fitted with circular escape openings. Despite this, pot catches typically contain a large proportion of sub-legal sized crab. This implies increased labor-intensive sorting which can lead to crab becoming injured, loosing limbs or delayed mortality. Such consequences negatively impact the sustainability of the fishery. In this study, we examined the potential of two new pot designs and longer soak times to reduce undersized crab catches in comparative field trials. A design consisting of a tarpaulin panel on the pot entrance (intended to prevent undersized individuals from gaining traction and entering) was found to be no better at reducing undersized catches than the currently used commercial design fitted with escape openings. A second design with a baited lower chamber (which could be accessed through the pot floor via escape openings) was intended to motivate undersized crab to escape more readily. If fished commercially, any crab in the bottomless lower chamber would be left behind on the seabed upon hauling. This design was found to have minimal effects on sublegal catches. However, increasing the soak time of the currently used commercial design from 1 day to 4 days reduced undersized crab catches substantially. This effect is likely related to bait becoming exhausted over time, thereby increasing the opportunity and motivation of sublegal crab to find and exit the pot through the mandatory escape openings. Laboratory-based behavioural observations using the panel design indicated that entry was dependent on crab orientation and that crab were less successful at entering than for the commercial design. However, all sizes of crab used an unintentional fold in the panel to increase their entrance probability. This may explain the lack of success of this design during the field trials. We conclude that ensuring bait is exhausted by employing longer soak times than is typically used by fishers would reduce catches of undersized crab in the fishery.

In the Barents Sea Norwegian pot fishery for snow crab (Chionoecetes opilio), fishing effort regulations and bait expenses create incentives to improve the catch rates. The fishery also currently captures a large proportion of sub-legal sized crab which must be sorted out and released. In this study, we used comparative fishing trials to determine the size dependent capture efficiency of three modified pot types designed to address these issues. A pot constructed with 40 mm mesh caught ∼35% more (CPUE, number of individuals per soak time) large crab (≥ 100 mm carapace width [CW]) than the pot typically used in the commercial fishery (140 mm mesh). However, it also retained massive amounts of small individuals (< 100 mm CW). The addition of four stadium shaped escape openings into the 40 mm and 140 mm mesh designs resulted in large reductions in catches of small crab, but also a ∼30% reduction in large crab. Analysis of size dependent catch comparison rates and selectivity parameters supported the CPUE findings. Of the tested designs, catches were best optimized by the currently used commercial pot. However, we conclude that a small mesh pot with escape openings has the potential to increase catches of large crab and reduce catches of non-commercial small crab. Further development of this design, particularly in terms of the dimensions of the escape openings, is therefore required.

During a 2018 retrieval cruise for abandoned snow crab (Chionoecetes opilio) pots in the Barents Sea, approximately 8600 pots abandoned 1.5 years earlier were recovered. Forty-three percent of a subsample of 1000 pots contained snow crabs, with an average of three crabs per pot. Most of the crabs were alive (~98%) and dominated by large males. Pinch injuries and limb loss were common and tended to decline with increasing crab size. Reflex testing showed that the crabs were vital (i.e. the crabs moved their legs, chelipeds and maxillipeds when stimulated), which was supported by a relatively high meat content. However, energy reserves in the digestive glands (hepatopancreas reserves) were low, indicating overall energy deficiencies. Our results indicate considerable unaccounted mortality due to self-baiting, continued catch and cannibalism. The findings demonstrate that snow crab pots which are lost or abandoned in the Barents Sea fishery maintain huge potential for ghost-fishing impacts.

Size selection in active fishing gears is a continuous process and undersized fish may escape during the whole fishing operation. Fish that escape during the surface hauling operation are likely to experience higher mortality due to barotrauma-related stress than fish escaping at the fishing depth during the towing process. A well-functioning selectivity device should therefore select mostly at depth for enhancing survival probabilities of escaping fish. The current gear regulation in the Norwegian demersal seine fishery is likely to cause large proportion of undersized fish to escape at the surface. In this study, we estimated surface selection of haddock and cod in demersal seine by using an automatic release system and a small meshed codend that collected fish escaping during surface hauling. The collecting bag contained 19% undersized haddock compared to 10% in the conventional square-mesh codend indicating that about 50% of undersized haddock brought to the surface were released. The proportions of undersized cod were 8% for the collecting bag and 1% for the conventional square-mesh codend. These results demonstrate that surface selection is significant for both haddock and cod. Based on this finding, we discuss methods to improve size selectivity at the fishing depth

The aim of this behavioural study was to identify potential feeding attractants to be incorporated in an alternative longline bait for Atlantic cod. The attractants should be based on low-cost surplus resources that are not used for human consumption. The food search and feeding responses of wild caught cod to eight attractants made from products from the fishing and aquaculture industry were compared to traditional squid bait in a laboratory study. All attractants tested triggered feeding responses in cod, indicating that there are several by-products from the fishing industry that have potential as an attractant for an artificial longline bait. The three most effective attractants were herring processing by-products, sand eel hydrolysate and hydrolysate by-products from the shrimp industry, which all elicited stronger food search and feeding responses than squid. Our results indicate that both free amino acids and other unidentified compounds are important in eliciting feeding responses in cod. Thus, attempts to identify efficient feeding attractants to be incorporated in alternative baits should be based on using complete aqueous extracts, rather than isolating a mixture of potent components.

Luminescent netting increases the catch rate of snow crabs (Chionoecetes opilio) over short soak times (1 d), however the commercial fishery often requires longer soak periods, up to 1 week. Building on previous research, this study investigated the catch efficiency and size selectivity of pots with luminescent netting over long soak times (144-336 h) in the inshore snow crab fishery of Newfoundland, Canada. A total allowable catch and individual quota allocation management system for snow crab is regulated in Canada and using luminescent netting to increase catch rates would reduce the carbon footprint of the fishery by reducing days fished. Our results showed that luminescent pots had a 21.6 % and 18.3 % higher catch-per-unit-effort (CPUE; number of crabs per pot) of legal-sized crab and sub-legal sized crab, respectively, than control pots; with no difference for soft-shelled crab. Additionally, no significant differences were shown for size selectivity over the range of car-apace widths observed between luminescent and control pots. Little other bycatch (female snow crab and un-wanted species) were caught in either pot treatments. This study shows that luminescent netting increases the efficiency of the snow crab fishery, which provides economic and environmental benefits.

In this study, we investigated luminescent netting as a means to improve the catch rates of snow crabs Chionoecetes opilio. A laboratory experiment was conducted to investigate the intensity and duration of luminescence using time‐lapse photography. We exposed experimental traps to five different treatments of UV light to excite the luminescent fibers in the netting. Our results showed that luminescent netting can be effectively activated to emit light, and that the resulting intensity and duration of luminescence emitted over time depends on the initial duration of UV exposure and the source of light. A fishing experiment was subsequently conducted in eastern Canada to compare the catch rate of traditional and luminescent traps, and to determine how soak time affected catch rate. Results indicate that the effect of luminescent traps on the CPUE (measured as number of crab per trap) depended on the soak time. The CPUE was significantly higher (a 55% increase) in luminescent traps that underwent relatively short soak times (~1 d), but when soak times were longer (~8 d), the CPUE was not significantly different.