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Recreational fishers often consume their catch, which may expose them to environmental contaminants. However, targeted risk assessment for exceeding the tolerable weekly intake (TWI) of a specific contaminant is often lacking, as specific data on the extent of fishing, consumption rates, and contamination of the caught seafood is needed. This study examined recreational fishing for nephrops (Nephrops norvegicus) at several different locations in Western Norway to identify important risk factors. The combination of a field survey to examine actual catches, interviews of recreational fishers about their seafood eating habits, and the analysis of total mercury (Hg, as a proxy for methylmercury (MeHg)) in recreationally captured nephrops allowed to conduct a targeted risk assessment. Recreational fishers consumed on average seven nephrops per meal, and 73% of the fishers ate nephrops once a month or more. The average Hg concentrations in nephrops were below the legal maximum level (100 ± 50 μg/kg wet weight (mean ± SD)). Hg concentrations in female nephrops were significantly higher than in males at the same size, and differed significantly between locations. The recreational fishers in this study were not at risk of exceeding the TWI for MeHg from consuming nephrops only; however, there is a general risk of exceeding TWI for MeHg as 70% of the fishers reported a frequent consumption of fish for dinner. Targeted risk assessments on recreational fishers may reveal particularly vulnerable populations where national dietary surveys may miss the highest seafood consumers. Graphical abstract

We document that Atlantic bluefin tuna (BFT) began making a comeback from 2012 onwards into Norwegian waters, after several decades of absence, in parallel with an overall increased abundance recorded for eastern BFT. This study explores the distribution, biology and ecology of BFT reestablishing in Norwegian waters. We analyzed commercial catch and bycatch data including biological data on weight, length and age of BFT from 2016–2018. Predominantly larger (overall range in catches: 120−465 kg in weight and 184−297 cm in straight fork length (SFL)) adult individuals between 6 and 14 years old have recently started to revisit Norwegian waters. Numerous recently documented BFT observations were reported in this study, and a significant increase was detected from 2012 (n = 1) to 2018 (n = 105) (p < 0.01). Schools of BFT were observed predominantly from June to December, including the northernmost registered observation in history recorded at 76.2 °N in September 2018. Atlantic bluefin tuna has now reestablished and has shown a positive comeback to its historical migration patterns in Norwegian waters, where it has expanded its feeding areas towards the north. publishedVersion

Atlantic cod (Gadus morhua) in Skagerrak are structured into distinct ecotypes or stock components that have been severely depleted over the past decades. To improve our understanding of how local commercial and recreational fisheries influence cod stocks, we investigated whether these user groups target different stock components of cod. Cod were sampled from the recreational rod and line fishery and from commercial shrimp trawlers catching cod as by-catch. Based on a large set of single nucleotide polymorphisms (SNPs), we defined a subset of 27 semi-diagnostic SNPs designed to discriminate between two cod stock components: “inner fjord” cod and “North Sea” cod, designated by their dominant habitat preferences. Genetic assignments of fishery-caught cod indicated that 4% of individuals caught by shrimp trawlers belonged to the inner fjord cod component and 96% to the North Sea, whereas among cod caught by recreational fishers, the estimated percentages were 11.8 and 88.2%, respectively. Our findings confirm the existence of two sympatric cod stock components in coastal Skagerrak, indicating that existing management units are biologically inappropriate and should be reconsidered. Furthermore, more attention should be given to recreational angling to reduce fishing mortality on the depleted inner fjord cod component.

Catch-and-release (CR N = 11) were caught on angling gear using commonly used fishing lures, and tagged with both pop-up satellite archival tags (PSATs) and acoustic transmitters. Survival was determined by the vertical migration patterns of individuals measured by the tags during individual monitoring periods ranging from 3 to 248 days (median 80 days) after the C&R event. No short-term mortality was observed post release. In terms of long-term survival, eight halibut were confirmed to have survived the monitoring periods while one halibut had insufficient data. For the other two individuals, the acoustic transmitters showed a cessation of vertical movement after 38 and 44 days, which could neither be verified nor disproven by the PSAT recordings (due to earlier detachment and tag malfunction of the PSATs). Since premature tag shedding was frequent in this study, it cannot be concluded if the cessation of vertical movement was because of tag shedding or delayed mortality. The results of this study indicate that Atlantic halibut is resilient to C&R angling, and that C&R of Atlantic halibut may be an effective management strategy to reduce fishing-induced mortality. However, the effects of severe hooking injuries, impacts on smaller individuals, and potential sublethal consequences of C&R were not covered in this study, and are still poorly understood. To minimize negative impacts of C&R and to promote fish welfare, fisheries managers are encouraged to implement best practice C&R angling guidelines for Atlantic halibut.

Capture-based aquaculture (CBA) of Atlantic cod (Gadus morhua) has become increasingly important in recent years, and increased attention is being paid to animal welfare issues linked to these activities. Earlier studies showed that some cod develop secondary exophthalmia in captivity. This study investigated the development of secondary exophthalmia in two groups of wild-caught cod, one of which was exposed to rapid decompression causing acute barotrauma (treatment group) while the other was not (control group). Photographs and radiographs before and up to 33 days after barotrauma revealed a significant increase in overall eye protrusion caused by an accumulation of gas in the orbita in the treatment group, first observed on day 9 after decompression, while no protrusions were observed in the control group. Barotrauma was thus identified as an important trigger for the development of secondary uni- or bilateral exophthalmia of wild-caught cod. Two underlying mechanisms are suggested, where the more likely is residual swim bladder gas taking the route of least resistance, while the less likely is the exsolution of gas from the blood. Our results have implications for a wide range of contexts in which cod are rapidly brought to the surface from great depth.

Este artículo contiene 19 páginas, 7 tablas, 4 figuras., Marine recreational fishing (MRF) is a high-participation activity with large economic value and social benefits globally, and it impacts on some fish stocks. Although reporting MRF catches is a European Union legislative requirement, estimates are only available for some countries. Here, data on numbers of fishers, participation rates, days fished, expenditures, and catches of two widely targeted species were synthesized to provide European estimates of MRF and placed in the global context. Uncertainty assessment was not possible due to incomplete knowledge of error distributions; instead, a semi-quantitative bias assessment was made. There were an estimated 8.7 million European recreational sea fishers corresponding to a participation rate of 1.6%. An estimated 77.6 million days were fished, and expenditure was €5.9 billion annually. There were higher participation, numbers of fishers, days fished and expenditure in the Atlantic than the Mediterranean, but the Mediterranean estimates were generally less robust. Comparisons with other regions showed that European MRF participation rates and expenditure were in the mid-range, with higher participation in Oceania and the United States, higher expenditure in the United States, and lower participation and expenditure in South America and Africa. For both northern European sea bass (Dicentrarchus labrax, Moronidae) and western Baltic cod (Gadus morhua, Gadidae) stocks, MRF represented 27% of the total removals. This study highlights the importance of MRF and the need for bespoke, regular and statistically sound data collection to underpin European fisheries management. Solutions are proposed for future MRF data collection in Europe and other regions to support sustainable fisheries management., Institut Français de Recherche pour l’Exploitation de la Mer; French Ministry of Fisheries Management; Greek National Data Collection Programme; European Commission, Data Collection Framework; Department for Environment, Food and Rural Affairs, Grant/Award Number: MF1221, MF1230 and MI001; Norges Forskningsråd, Grant/Award Number: A framework for science-based management of marine recreational fisheries in Norway (267808); State Department of Agriculture, Food Security and Fisheries Mecklenburg- Western Pomerania; Interreg IVa 2 Seas, Grant/Award Number: GIFS project; Dutch Ministry of Economic Affairs, Grant/Award Number: WOT (Wettelijke Onderzoekstaken) programme; European Fishery Fund - Axis 4, approved by FLAG; Department of Environment, Planning, Agriculture and Fisheries from the Basque Government; Government of Galicia, Grant/Award Number: RECREGES project (ED481B2014/034-0)

Studying the sublethal effects of catch-and-release (C&R) is challenging, as there are several potential sources of bias. For example, if behavioural alterations immediately after the release event are to be studied, separation of tagging effects from actual C&R effects is required, which is a challenge in the wild, particularly in marine environments. To investigate the effects of C&R on Atlantic cod (Gadus morhua) in their natural environment, 80 cod were caught in fyke nets, fitted with acoustic transmitters, and released. After recovery from tagging and handling for at least 14 days, nine individuals were recaptured and released at least once during experimental angling, following best release practice. All cod survived the C&R event and did not show any large-scale behavioural changes (i.e., changes in diel vertical migrations). However, analysis of small-scale vertical movements showed that three individuals underwent short-term alterations (e.g., reduced or increased swimming activity). This study showed that pretagging fish with acoustic transmitters before experimental angling is an option when investigating fish behaviour immediately after the release event in marine environments. Moreover, release guidelines for cod should be developed, as cod can recover quickly if caught in shallow waters (

Marine recreational fishing (MRF) has been shown to substantially contribute to fishing mortality of marine fish. However, European MRF catches are only quantified for a small number of stocks, so it is unclear whether a significant part of fishing mortality is excluded from stock assessments. This study estimated: (i) European MRF removals, which were defined as landings plus dead releases; and (ii) impact at stock level by comparing the percentage contribution to total removal by MRF and commercial fishing. As MRF data were limited for some European countries, catches were reconstructed using a mixture of average release proportions, average fish weights, and extrapolation using the catch per fisher of the nearest country providing catch estimates. Where catch reconstructions exceeded 50%, data were excluded from further analysis. Furthermore, as MRF survey methodology can be variable, semi-quantitative estimates of bias and error were calculated for each stock. Only 10 of the 20 stocks assessed in this study had sufficient MRF data for full reliable estimates. Percentage contribution to total removals (MRF + commercial removals) by MRF ranged between 2% for Atlantic mackerel in the North Sea and Skagerrak and 43% for Atlantic pollack in the Celtic Seas and English Channel. The biomass removed ranged between 297 (± 116) tonnes (Atlantic cod in the western English Channel and southern Celtic seas) and 4820 (± 1889) tonnes (Atlantic mackerel in the North Sea and Skagerrak), but the errors were substantial. Additionally, the bias in the estimated removals was low for most stocks, with some positive biases found. The present study indicates that removals by MRF can represent a high proportion of the total removals for some European marine fish stocks, so inclusion in stock assessments should be routine. To achieve this, regular surveys of MRF are required to collect data essential for stock assessments.

Atlantic cod (Gadus morhua) caught in recreational fisheries are commonly released, often with barotrauma after rapid decompression. Mouth-hooked, non-bleeding cod kept in a floating net pen showed mortalities ≥40% when angled from >50 m depth, likely because of cumulative stress from ongoing barotrauma and exposure to warm surface water. In a natural setting, however, cod have the opportunity to descend after release and are not restricted to the surface. In a follow-up study, 97.8% of similarly selected cod managed to dive following immediate release, whereas 2.2% were floaters. No mortality was observed for divers kept in cages, which were lowered to capture depth for 72 h. While the floaters would likely have died in a natural setting, no mortality was observed when they were recompressed and kept at capture depth for 72 h. The occurrence of swim bladder ruptures, swollen coelomic cavities, venous gas embolisms, and gas release around the anus was significantly influenced by capture depth (range 0–90 m). A supplementary radiology study showed inflated swim bladders in 87% of the cod after 72 h, and most barotrauma signs had disappeared after 1 month. This study encourages investigation of survival potential for physoclistous species when high mortalities are assumed but undocumented. Matching natural post-release and containment environment is essential in the experimental setup, as failure to do so may bias survival estimates, particularly when a thermocline is present. Assuming minimal predation, short-term mortality of cod experiencing barotrauma is negligible if cod submerge quickly by themselves and are otherwise not substantially injured. Survival of floaters may be increased by forced recompression to capture depth. Sublethal and long-term impacts of barotrauma remain to be studied. To ensure that cod have sufficient energy to submerge, anglers are encouraged to avoid fighting the fish to exhaustion and to minimize handling before release.

Better knowledge of food search behavior in fish is essential for studies that aim to improve longline fishing, particularly through bait development. This review provides an overview of our understanding of how fish detect and locate sources of food odour, focusing on the stimuli and sensory modalities involved, and on factors that affect feeding activity. Studies that identify feeding attractants and efforts to develop alternative longline baits are presented. The review reveals that such studies are few in number, and that to date there are no alternatives to traditional baits in commercial longlining despite the growing demand for these resources, which are also used for human consumption. The chemical compounds that elicit food search behavior differ from species to species, and species selectivity could be improved by incorporating specific feeding attractants in manufactured baits. The unique properties of chemical stimuli and odour dispersal form the basis for improving longline efficiency through the development of a long-lasting bait. Vision is important in prey capture, and manufactured baits can be made more visible than natural baits by increasing the contrast (e.g. via fluorescent or polarising coatings) and creating motion through buoyancy. Physical properties such as size, shape, texture and strength can also be manipulated in a manufactured bait to improve catch efficiency. Knowledge obtained from studies of various aspects of food search behaviour is of paramount importance for future research aimed at alternative bait development and improving longline fishing. publishedVersion

Ferter, Keno et al., While catch-and-release (C&R) is a well-known practice in several European freshwater recreational fisheries, studies on the magnitude and impact of this practice in European marine recreational fisheries are limited. To provide an overview of the practice and magnitude of C&R among marine recreational anglers in Europe, the existing knowledge of C&R and its potential associated release mortality was collected and summarized. The present study revealed that in several European countries over half of the total recreational catch is released by marine anglers. High release proportions of >60% were found for Atlantic cod (Gadus morhua), European sea bass (Dicentrarchus labrax), pollack (Pollachius pollachius), and sea trout (Salmo trutta) in at least one of the studied European countries. In the case of the German recreational Baltic Sea cod fishery, release proportions varied considerably between years, presumably tracking a strong year class of undersized fish. Reasons for release varied between countries and species, and included legal restrictions (e.g. minimum landing sizes and daily bag limits) and voluntary C&R. Considering the magnitude of C&R practice among European marine recreational anglers, post-release mortalities of released fish may need to be accounted for in estimated fishing mortalities. However, as the survival rates of European marine species are mostly unknown, there is a need to conduct post-release survival studies and to identify factors affecting post-release survival. Such studies could also assist in developing species-specific, best-practice guidelines to minimize the impacts of C&R on released marine fish in Europe. © 2013 International Council for the Exploration of the Sea.

The European eel (Anguilla anguilla) is a commercially and recreationally important fishery target species. In the last decades, the eel has experienced dramatic stock declines and has been listed as critically endangered. To reduce fishing mortality, several European countries have closed the fishery or introduced stricter management measures which increase the likelihood of catch-and-release in the recreational fishery. This study investigated hook shedding mechanisms of deep-hooked, line-cut eels via radiography, and quantified hook shedding rates, post-release mortality and sub-lethal effects in captivity. Eels were caught with four different hook treatments, monitored in a tank for 23 weeks, and radiographed 0, 1, 3, 10, 24, 54, 115 and 163 days after capture. After 163 days, total hook shedding rate was significantly higher for smaller hooks (41.2%) compared to larger hooks (0.0%), and increased with fish length. Post-release mortality rates ranged between 27.3% and 50.0% after 23 weeks (not adjusted for handling and holding) and did not differ significantly between hook treatments. The majority of dead eels showed gastric perforations caused by the hooks leading to internal haemorrhaging and the intrusion of digestive fluids into the body cavity inducing lethal degradation and inflammation of vital organs. Anglers are encouraged to minimise bycatch of eel in countries where eel harvest is prohibited. Anglers targeting eel should use selective and appropriate fishing gears, baits and tactics (e.g. very large hooks, immediate hook setting after a bite) to reduce deep hooking and the catch of undersized eels, ultimately promoting the eel's conservation. publishedVersion