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When discarded from bottom trawl fisheries, survival of Nephrops norvegicus may be sufficiently high that this species can be exempted from the EU Landing Obligation. In three studies, Nephrops were sampled from trawlers in northern European waters, and the fate of individuals monitored for a minimum of 13 days in onshore tanks. Winter estimates of captive survival (means ± 95% confidence intervals), including immediate mortality during catch sorting, were 62 ± 2.8% for the West of Scotland, 57 ± 1.8% for the Farne Deeps (North Sea), and 67 ± 5.4% for the Skagerrak. The Farne Deeps fishery is not active in summer, but captive survival rates in summer in the other two areas were reduced to 47 ± 3.4% for West of Scotland and 40 ± 4.8% for the Skagerrak. Linear modelling of the West of Scotland and Skagerrak data suggested that higher survivals in winter were related to colder water or air temperatures, although temperatures during captive observation may also have had an impact. Net modifications in the Skagerrak study had an effect on survival, which was higher for Nephrops sampled from nets equipped with the more selective Swedish sorting grid compared to Seltra trawls.

16 pages, 6 figures, 4 tables, supplementary material https://www.int-res.com/articles/suppl/m674p173_supp/, The Norway lobster Nephrops norvegicus is one of the most important marine resources for European fisheries. However, overfishing has caused the stocks to decline over the last decades, particularly in the Mediterranean Sea. The implementation of no-take marine reserves could change these current trends, thus achieving a more sustainable fishery. The effectiveness of no-take reserves depends on optimal size design, and because of this, new behavioural data on the spatial ecology of the species are of pivotal importance. Here, for the first time, we investigated the spatial movements and daily activity patterns of Norway lobster in a deep-water (315-475 m depth) no-take marine reserve of 10 km2 in the continental slope of the northwestern Mediterranean Sea, by combining acoustic tracking and tagging-recapture procedures. The results revealed the territorial behaviour of Norway lobster, centred in small exclusive individual areas where most displacements took place at midday. We found that once settled in a place, their home ranges reached approximate sizes of 17.75 to 736.25 m2, suggesting that no-take marine areas focussed on recovering Norway lobster populations do not require large extents to be effective. Tag-recapture data indicated minimal spillover of biomass, implying that Norway lobsters are site settled and do not perform large movements. Future studies on larval spread and recruitment would be necessary to focus on the possible spillover benefit for fisheries. The acoustic telemetry system used in the present experiment effectively revealed the range of movement of individuals, and thus represents a promising monitoring tool to assess no-take marine reserve sizes and reciprocal spacing for deep-water demersal resources, M.V. was supported by a predoctoral fellowship of the FPU program of the Spanish Government (FPU18/01775). J.N. was funded by the Spanish National Program Ramón y Cajal (RYC-2015-17809), Ministry of Science and Innovation, Spain. I.M. was funded by a MSCA-IF-GF (ID:893089, H2020-EU.1.3.2, European Commission) and received financial support from the project SASES (RTI2018-095112-B-I00). This work was developed in the framework of the Joint Research Unit Tecnoterra (ICM-CSIC and UPC). The results reported herein arose from the project RESNEP (CTM2017-82991-C2-1-R), financed by the Spanish Ministry of Economy and Competitiveness, Spain. This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

Genotyping by sequencing along with high throughput sequencing approaches allows for the rapid development and discovery of variable markers such as microsatellites, which can be highly informative for population genetics. These approaches, along with combinatorial barcoding techniques and a novel genotyping protocol, were employed to examine the population structure of commercially valuable fisheries species, Nephrops norvegicus. Results suggest at least four genetically distinct groupings of the species across the sampled distribution and the presence of isolation by distance. No evidence for genetic bottlenecks were found in any population, however the genetic structure observed in this study does not correspond to current fisheries management delineations. This study is the first to apply microsatellite markers distribution-wide for this species, revealing a population structure for Nephrops norvegicus important for informing management of this widely fished species.

Impact studies of chronic bottom trawling aiming to reveal long-term effects on benthic organisms are often hampered by the lack of comparable untrawled conditions and the difficulty in assessing the spatial distribution of trawling intensity. We sampled soft-seafloor macrofauna over a precise trawling gradient in the Kattegat using hourly vessel monitoring systems and logbooks. The gradient included the establishment of a marine protected area (MPA), where trawling intensity declined sharply to zero. Our results show shifts in the macrofauna assemblage and non-linear responses, with decreases in the number and diversity of species at low to medium trawling intensities. The benthic community was dominated by burrowing brittle stars, of which one species, Amphiura chiajei, increased in abundance from low to medium trawling intensities. We interpret this positive response to increasing trawling intensities as a consequence of reduction in predation by benthivorous flatfish and Norway lobster Nephrops norvegicus, which are significant catches of the fishery. The response was supported by a corresponding trend towards lower abundance of the dominating brittle stars following enforcement of the MPA and presumably an increase in benthivore density and predation pressure within the MPA. We conclude that chronic bottom trawling reduces diversity and may boost the abundances of species resistant to bottom trawling. The results emphasize the need to consider food web effects when assessing the impact of bottom trawling.

Expeditious uptake of quad-rig trawling in the economically important Irish fishery for Nephrops norvegicus outpaced technical understanding of this newly introduced gear. The main driver for its introduction is increased catch rates of Nephrops. Higher Nephrops discard rates associated with quad-rig trawling are likely to be problematic under the landing obligation unless size selectivity can be improved. Catch comparison methods are suitable for assessing the performance of fishing gear modifications to reduce discards. Utilizing a quad-rig potentially increases the number of gears that can be included in a catch comparison study to four but current modeling methods are limited to two gears. Our study provides a new general multinomial mixed effects modeling framework that can be applied to two or more gears, elucidates how case-specific and choice-specific covariates may influence catch at length, and facilitates discussion on appropriate gear based management measures. Application of the method to catches from four different cod-end mesh sizes revealed significant effects of carapace length, catch weight and net position, on the numbers of Nephrops retained in each cod-end. Results suggest that management measures which specifically address different catch profiles associated with different numbers of trawling rigs are required to optimize Nephrops size selectivity.

Recent research has indicated through chemical tagging of some species of decapod crustacean that the mesocardiac, zygocardiac, and pterocardiac ossicles of the gastric mill are retained through molting and contain apparent growth increments potentially indicative of age. Though other recent studies have suggested that in some decapod species, these ossicles are either lost in the stomach exuvia at molting, or are partially resorbed prior to molting. This study investigated the fate of the gastric mill ossicles of Nephrops norvegicus throughout the molt cycle, in order to ascertain their utility for age determination. Wild-caught individuals were immersed in a calcein solution to stain the ossicles, reared in an aquaculture facility, and sacrificed at different stages of the molt cycle. In all individuals sacrificed less than 24 h after molting, the mesocardiac, zygocardiac, and pterocardiac ossicles of the gastric mill were found loose within the stomach of the individual, no longer attached to the stomach wall, among the disintegrated gastroliths. New ossicles are subsequently calcified postmolt to support the gastric mill and stomach wall. The same phenomenon of ossicle loss was also observed in two Austropotamobius pallipes individuals sacrificed 1 h postmolt. In some N. norvegicus individuals sacrificed at varying periods of time postmolt, the calcein stain was reincorporated into the newly calcified ossicles. It is suggested that this is because once the calcifying gastric mill is strong enough to cope with food, the old ossicles and gastroliths are digested, and their calcium, to which the calcein is bound, is resorbed. The results of this study indicate that the growth increments previously observed within the gastric mill ossicles of N. norvegicus are unlikely to be of annual periodicity, but are a result of the postmolt calcification process. It therefore seems unlikely that N. norvegicus can be directly aged using the gastric mill ossicles. This may be the case for a number of decapod crustacean species.

Source at http://dx.doi.org/10.12681/mms.19018. Creative Commons Attribution Non-Commercial Share Alike License 3.0 CC BY 3.0 Fish or crustaceans stuck in the fishing gear meshes can lead to operational problems in some fisheries and thereby affect the economic gain. However, mesh sticking probability has never been formally quantified as a part of the estimation of fishing gear size selectivity. Therefore, this study developed a size selection model and estimation procedure that, besides the size dependent retention and escape probabilities, includes the size dependent mesh sticking probability. The new method was applied to quantify the size dependent retention, sticking and escape probabilities for mantis shrimp (Squilla mantis) and Norway lobster (Nephrops norvegicus) in creels with 41 mm square mesh netting. The mesh sticking probability was found to display a bell-shaped curvature with a maximum value for a specific carapace length and decreasing probabilities for both smaller and bigger individuals. For mantis shrimp the maximum sticking probability was found for 32.5 mm carapace length with a value at 13.5%, while 63.1% and 23.4% of that size were respectively retained inside the creels and escaped. For Norway lobster the maximum sticking probability was 2% and occurred for 34.0 mm carapace length. The method and estimation procedure presented in this study might be applicable for quantifying mesh sticking probability as an integral part of future fishing gear size selectivity studies on other species and fisheries.

The European Common Fisheries Policy has in its 2013 reform increased in complexity, such as a call for coherence with the Marine Strategy Framework Directive and a landing obligation, posing new requirements and challenges to managers, scientists and the fishing industry. Therefore, re-evaluations of current practice are important as a basis for management actions. The Swedish fishery for Norway lobster (Nephrops norvegicus) in the Kattegat–Skagerrak area provides an interesting case study of relevance to emerging policies. Sprung from an unbalance in available fish- and Nephrops quotas and an ambition to protect coastal areas, the current fishery has been directed towards three separate fisheries (mixed trawling, directed trawling using a sorting grid and creeling). Studying direct and indirect effects from alternative Swedish quota allocations among gear types is therefore interesting. Accordingly, a screening study was conducted, taking into consideration area-gear interactions in catch rates, to compare the three different fisheries regarding quantified pressures on the target species, the by-catch species, and on the seafloor, as well as to qualitatively discuss social and economic dimensions. In the next step, alternative quota allocations were studied. In Swedish fisheries, we show that creeling offers a substantial reduction of fishing mortality of both undersized Nephrops and fish and a reduced seafloor pressure per landed kilo of Nephrops. Given that the fishing areas in many cases may be interchangeable between gears, allocating a larger quota share to creels in the Swedish fishery would therefore contribute to the integration of fisheries- and environmental management as called for in the new policies.

Norway lobsters, Nephrops norvegicus, are sediment-dwelling decapod crustaceans that excavate burrows from which they make short excursions to feed by predation and scavenging. The females of this species are known to reside within their burrows for an extended period of time over the winter while brooding their eggs. The aim of this study was to assess the likelihood of these females being able to feed during this brooding period. Biophysical and biochemical measurements that had previously been shown to change with starvation under laboratory conditions in male N. norvegicus were taken for female N. norvegicus under similar conditions. These measurements were also compared in both sexes obtained from monthly trawl samples from the Clyde Sea Area, Scotland, UK, together with trawl composition data. The laboratory study showed that the hepatosomatic index, and the copper, lipid and water content of the hepatopancreas can be used as indicators of the state of starvation in females, as in males. In the wild, both sexes have reduced nutritional status during the winter, but not to the degree seen in animals starved for 20 weeks in aquarium trials. This study does not support the hypothesis that females cease feeding over winter, during their brooding period. Firstly, some females were unable to sustain ovary development during starvation under controlled conditions, contrary to field observations. Secondly, field data suggest that there is no sex-specific reduction in nutritional status.

The marine environment is changing and becoming less stable as a result of direct (e.g. lower pH) and indirect (e.g. salinity fluctuations from changing rainfall) effects of climate change. The larval stages may be a bottleneck for reproductive success and recruitment, therefore the potential for environmental stressors to impact upon larval recruitment is high; the ability to tolerate environmental stress in early life history is crucial to an individual's overall fitness. This study investigated the effect of hypercapnia and salinity stress on the early life stages of the Norway Lobster Nephrops norvegicus . Sensitivity to hypercapnia was shown to be highly brood specific with large differences in mortality between broods under hypercapnic stress. Furthermore, this environmental stressor was demonstrated to increase the energetic demand on the larvae, which could potentially have a negative effect later in development. Salinity stress experiments were not designed to test brood specific effects but did demonstrate increased energy usage (higher MR and lower weight) under salinity stress. Although the larvae were tolerant to present levels of salinity stress future changes in this stressor may alter species distribution. This study demonstrated that environmental stressors have the potential to have a large effect on future recruitment. Further, future studies need to consider mechanisms that affect an individual's tolerance from conception, such as epigenetics, maternal provisioning and genetic factors, to determine what makes some individuals tolerant where others are not.

Meta-analysis of marine biological resources can elucidate general trends and patterns to inform scientists and improve management. Crustacean stocks are indispensable for European and global fisheries; however, studies of their aggregate development have been rare and confined to smaller spatial and temporal scales compared to fish stocks. Here, we study the aggregate development of 63 NE Atlantic and Mediterranean crustacean stocks of six species (Nephrops norvegicus, Pandalus borealis, Parapenaeus longirostris, Aristeus antennatus, Aristaeomorpha foliacea and Squilla mantis) in 1990–2013 using biomass index data from official stock assessments. We implemented a dynamic factor analysis (DFA) to identify common underlying trends in biomass indices and investigate the correlation with the North Atlantic Oscillation (NAO) index. The analysis revealed increasing and decreasing trends in the northern and southern NE Atlantic, respectively, and stable or slowly increasing trends in the Mediterranean, which were not related to NAO. A separate meta-analysis of the fishing mortality (F) and biomass (B) of 39 analytically assessed crustacean stocks was also carried out to explore their development relative to MSY. NE Atlantic crustacean stocks have been exploited on average close to FMSY and remained well above BMSY in 1995–2013, while Mediterranean stocks have been exploited 2–4 times above FMSY in 2002–2012. Aggregate trends of European crustacean stocks are somewhat opposite to trends of fish stocks, suggesting possible cascading effects. This study highlights the two-speed fisheries management performance in the northern and southern European seas, despite most stocks being managed in the context of the European Union's Common Fisheries Policy.

A proposed method to determine chronological age of crustaceans uses putative annual bands in the gastric mill ossicles of the foregut. The interpretation of cuticle bands as growth rings is based on the idea that ossicles are retained through the moult and could accumulate a continuous record of age. However, recent studies presented conflicting findings on the dynamics of gastric mill ossicles during ecdysis. We herein study cuticle bands in ossicles in four species of commercially important decapod crustaceans (Homarus gammarus, Nephrops norvegicus, Cancer pagurus and Necora puber) in different phases of the moult cycle using dissections, light microscopy, micro-computed tomography and cryo-scanning electron microscopy. Our results demonstrate that the gastric mill is moulted and ossicles are not retained but replaced during ecdysis. It is therefore not plausible to conclude that ossicles register a lifetime growth record as annual bands and thereby provide age information. Other mechanisms for the formation of cuticle bands and their correlation to size-based age estimates need to be considered and the effect of moulting on other cuticle structures where ‘annual growth bands’ have been reported should be investigated urgently. Based on our results, there is no evidence for a causative link between cuticle bands and chronological age, meaning it is unreliable for determining crustacean age.

The development of the vessel monitoring system (VMS) in the recent years has offered high-resolution data to map the distribution and intensity of fishing activities and contributed to enhancing the potential identification of fishing impacts. However, impacts could vary at very small scale and the resolution of VMS data might not be fine enough. Other proxy could be used, such as trawl marks visible on the seabed observed by underwater video or side-scan sonar to evaluate small-scale trawling effort. In the Bay of Biscay, an underwater video survey of the Nephrops norvegicus fishing ground was conducted and provided environmental characteristics such as depth and number of trawl marks at 152 transects. The relevance of observed trawl marks as a small-scale proxy of trawling effort was tested depending on the sediment type. The model showed a significant positive relation between density of marks and trawling effort for all sediments together but a different relation for each sediment type. Considering each sediment type separately, the unexpected high number of marks observed on sands could be linked with cohesive interactions between calcium carbonates particles while the low number of marks on fine lithoclastic muds could be due to sediment reworking and bioturbation. We conclude that the impact of trawling on the seabed varies with the type of sediments, hydrodynamic parameters, bioturbation and trawling intensity, leading to a very complex relationship. Trawl marks observed on video footage thus could be used as a proxy of trawling effort among the same type of sediment and not for fine lithoclastic muds.

Recent advances in the knowledge of the basic requirements to sustain captured lobsters, combined with improved transport links, has seen a dramatic expansion in the sale of live Nephrops norvegicus. In this paper, we describe the effects of storage system type on the health of lobsters held for periods up to three weeks in order to develop an optimal protocol for Icelandic producers for whom logistical challenges have thus far hindered access to the live market. Nephrops were caught by creel and transported to a holding facility in tanks supplied by either a flow-through from a harbour bore or recirculating water via a filtration system, where they were maintained without being fed for a period of three weeks. During this time, lobsters were assessed for haemolymph biochemistry and hepatopancreas composition and health. It was found that lobsters from both systems used storage reserves from the hepatopancreas, showing a progressive decline in hepatopancreatic index, hepatopancreas protein and gly...

The western Irish Sea seasonal gyre is widely believed to play an important role in the local retention of resident larvae. This mechanism could be particularly crucial for the larvae of the heavily fished crustacean Nephrops norvegicus (L.), as their sediment requirements highly restrict where they are able to settle. As recent research suggests that the gyre may be becoming less retentive due to changes in atmospheric forcing, it is now crucial to understand how the gyre influences dispersal. This investigation addresses the hypothesis that shelf sea gyres reinforce larval retention using a biophysical model with vertical migration, habitat selection and temperature-dependent pelagic larval duration (PLD) configured to match the behaviour of N. norvegicus larvae. The results of this study suggest that the gyre does increase the likelihood that passive larvae remain within the western Irish Sea, on the condition that the larvae remain fixed at the depth of peak gyral flow. Retention rates are significantly lower when vertical migration is introduced, and there is no evidence that the gyre promotes larval retention amongst either vertically migrating larvae, or larvae that require muddy sediments for successful settlement. By contrast, vertical migration is shown to be favourable for retention in the eastern Irish Sea. PLD varies by a factor of two according to release date and location. The simulations suggest that whilst some highly limited and almost entirely unidirectional larval exchange may occur, the distinct sites largely rely upon local recruitment.

10 pages, 5 figures, 3 tables, supplementary information http://jeb.biologists.org/content/220/24/4624.supplemental, Animals fight over resources such as mating partners, territory, food or shelter and repeated contests lead to stable social hierarchies in different phyla. The group dynamics of hierarchy formation are not characterized in the Norway lobster (Nephrops norvegicus). Lobsters spend most of the day in burrows and forage outside of them according to a diel (i.e. 24 h-based) activity rhythm. Here, we use a linear and generalized mixed model approach to analyse, in seven groups of four male lobsters, the formation of dominance hierarchies and rank-related changes in burrowing behaviour. We show that hierarchies emerge within 1-3 days and increase in steepness over a period of 5 days, while rank changes and number of fights gradually decrease over a 5-day period. The rank position determined by open area fights predicts the outcome of fights over burrows, the time spent in burrows, and the locomotor activity levels. Dominant lobsters are more likely to evict subordinate lobsters from their burrows and are more successful in defending their own burrows. They spend more time in burrows and display lower levels of locomotor activity outside the burrow. Lobsters do not change their diel activity rhythms as a result of a change in rank, and all tested individuals showed higher activity at night and dusk compared with dawn and daytime. We discuss how behavioural changes in burrowing behaviour could lead to rank-related benefits such as reduced exposure to predators and energy savings, This work was supported by RITFIM project (CTM2010-16274; principal investigator: J.A.) founded by the Ministerio de Ciencia e Innovación (MICINN). V.S. is now supported by a Leibniz-DAAD Research Fellowship (no. 57235478)

The nutritional status of an animal is maintained through a balance between energy intake and energy expenditure, and in the natural environment can fluctuate due to limited food availability and behavioural changes that remove the animal from its food. The integrated physiological processes that underlie an animal's nutritional status can be measured biophysically or biochemically. The Norway lobster Nephrops norvegicus has been shown to survive long periods of time without food, which is advantageous when food availability is low, such as during the winter months or when access to food is reduced due to risks associated with predation. In this study N. norvegicus was subjected to nutritional stress (starvation) for a period of 20 weeks and various biophysical measures (hepatosomatic index [HSI], length: weight ratio, tissue water content, carbon: nitrogen ratio) and biochemical measures (copper, carbohydrate, lipids, protein, stable isotopes δ15N δ13C) were used to determine how these animals maintain themselves over this period of forced starvation. Results indicate that while there was no variation in the whole weight of each individual, the organ-specific weight of the hepatopancreas (HSI) decreased and there was a corresponding increase in the water content of the hepatopancreas (and tail muscle). In contrast to the findings of previous studies, reserves of lipids decreased within the hepatopancreas. Fuel resources of protein from the tail muscle were not utilised, but reciprocal change in the copper content of the haemolymph to the hepatopancreas is suggestive of a breakdown of haemocyanin. The results provide an initial indication of how N. norvegicus can survive for long periods of time without food, and identify some potential biomarkers for starvation that can be applied to animals caught from the field.

Øresland, V., and Ulmestrand, M. 2013. European lobster subpopulations from limited adult movements and larval retention. – ICES Journal of Marine Science, 70: 532–539. Adults and larvae of the European lobster, Homarus gammarus, were studied within and around the Swedish Kåvra lobster reserve (2.2 km2). Tagging of 4016 lobsters within the reserve showed that the lobsters have limited movement out of the reserve. Only 58 lobsters (1.4% of all tagged lobsters) were recaptured ≥1 km from the reserve and 5658 recaptures were obtained inside the reserve. Light trap catches showed that stage 1 larvae had a peak occurrence during

The angular crab Goneplax rhomboides is native to the north-eastern Atlantic and Mediterranean Sea. It has rarely been reported from the North Sea, with no evidence of sustain- able populations. Compiled survey data, however, revealed an increasing abundance of this spe- cies in the North Sea since 2000. The data were used to (1) describe the range expansion of the angular crab into the North Sea; and (2) to apply species distribution modeling (maximum entropy approach-MAXENT) to predict the potential habitats of this species. Habitats of species with a similar ecology were modeled to analyse habitat overlap and potential competition. The spatial and temporal patterns of records revealed that the expansion of the angular crab into the North Sea is due to natural larval dispersal rather than anthropogenic vectors. Modeled habitats of the angular crab showed a core distribution area along the Scottish coastline and in the southern North Sea. Sea bottom temperatures in February had the highest influence on the model results. We concluded that the angular crab has extended its distribution range from the north-eastern Atlantic to the North Sea, which was facilitated by an increase in water temperature and the pre- vailing hydrodynamics over the last decade. This was the first time that a benthic range expansion was observed in quasi real time for the North Sea. Habitats of the angular crab overlapped those of possible competitors to a large extent. However, co-existence of the species is expected rather than any negative effects resulting from the range expansion of the angular crab.

Crustacean life is dominated by the moult cycle, a series of regular physiological and behavioural changes that enable the organism to grow. A method is described to determine the individual stages in the cycle of the species Nephrops norvegicus. Based on a combination of carapace hardness and pleopod morphology, 14 stages and substages are identified. The technique is used to investigate changes in haemolymph total protein and haemocyanin across the cycle. Peaks are detected in both parameters at the final stage of intermoult and during active pre-moult suggesting an increase in metabolic activity. In addition to validating the moult staging method, the results highlight the importance of considering the underlying physiology of lobsters in either experimental or ecological studies.

The impact of different diets on the gut microbiota of reared Nephrops norvegicus was investigated based on bacterial 16S rRNA gene diversity. Specimens were collected from Pagasitikos Gulf (Greece) and kept in experimental rearing tanks, under in situ conditions, for 6months. Treatments included three diets: frozen natural (mussel) food (M), dry formulated pellet (P) and starvation (S). Gut samples were collected at the initiation of the experiment, and after 3 and 6months. Tank water and diet samples were also analyzed for bacterial 16S rRNA gene diversity. Statistical analysis separated the two groups fed or starved (M and P vs. S samples). Most gut bacteria were not related to the water or diet bacteria, while bacterial diversity was higher in the starvation samples. M and P samples were dominated by Gammaproteobacteria, Epsilonproteobacteria and Tenericutes. Phylotypes clustering in Photobacterium leiognathi, Shewanella sp. and Entomoplasmatales had high frequencies in the M and P samples but low sequence frequencies in S samples. The study showed that feeding resulted in the selection of specific species, which also occurs in the natural population, and might be associated with the animal's nutrition.

The Kattegat in the inner Danish waters has been trawled for at least 80 yr, but so far only few attempts have been made to quantify the trawl effort, its spatial distribution and its potential ecological impact on the benthic fauna. GIS-analyses of VMS-data from trawling in the Kattegat by both Danish (2005-2009) and Swedish (2007-2009) vessels show that 95% of all trawling occurs below 22 m depth. Most activity takes place on homogeneous benthic habitats with muddy sediment at depths below the halocline and with almost the same salinity across the entire area. Furthermore, the estimate of trawled area demonstrated that the habitats are nearly 100% impacted, and frequencies of trawling beneath 100 m depth can reach 20 events per year. Multivariate analysis of community composition could not discriminate between lightly trawled and heavily trawled areas. However, a strong habitat selectivity of the trawl activity and inter-correlation between trawl activity and depth-related community structures complicated interpretation of the results. Species with biological traits previously categorized as sensitive to physical disturbance showed higher abundance in areas with low trawl activity compared to areas with higher activity. Thus, the Kattegat has been impacted to an extent where areas with reference conditions for certain habitats below 22 m no longer exist. Consequently, it is unknown how the benthic communities would have appeared without trawl disturbance and, thus, difficult to determine the impact of continued disturbance.

Hematodinium and Hematodinium-like species have emerged in the last 3 decades as important parasitic pathogens of crustaceans worldwide, causing a significant economic loss to fisheries and related markets. In some species (notably the Tanner crab Chionoecetes bairdi), the parasite reportedly causes the cooked meat to taste bitter and aspirin-like. The bitter taste, together with the gross pathology of the infection, renders these crabs unmarketable. Surprisingly, no organoleptic tests have ever been conducted to date, and the cause for the bitter taste is still unknown. Nevertheless, it is generally assumed that the bitter taste occurs widely in cooked meats and products derived from crustaceans infected with Hematodinium. In the present study, we analysed the meat quality and organoleptic attributes after capture and during storage of Norway lobsters Nephrops norvegicus from Scottish waters that were either asymptomatic or symptomatic of patent Hematodinium infection. Results from the sensory evaluation of the cooked product indicate that tail meat from symptomatic N. norvegicus is bland in flavour and aftertaste, and more friable or sloppier in texture than meat from asymptomatic animals. As a consequence, infected meat tends to be less palatable, although surprisingly no bitter taste is reported. From an analytical point of view, tail meat from patently infected animals is at an advanced stage of autolysis, while no difference in microbial load is detected. These results suggest that Norway lobsters heavily infected with Hematodinium are of inferior marketing quality even after the tails have been cooked.

Recent studies of the fisheries for the Norway lobster, Nephrops norvegicus (L.), have illustrated the negative effects of pathogens and of the physiological stresses of capture processes on the exploitation of live animals and their products, and have identified mitigating measures. Firstly, having established that trawl capture of N. norvegicus is highly stressful, but that these animals have powerful physiological mechanisms of recovery, procedures for on-board recovery of animals destined for vivier transport to distant European markets have been implemented commercially, with significant improvements in survival rates. Such procedures also mitigate against the initiation of a stress-induced muscle necrosis. Secondly, measurements of post-mortem autolytic and spoilage processes have identified the existence of a post-capture 'handling window' of several hours which allows the whole or tailed products to be preserved, by icing or freezing, without detriment to quality. Commercial consortia of Scottish fishermen are exploiting this opportunity to extend product shelf-life by freezing at sea within this handling window. Thirdly, the well-documented infections of Scottish N. norvegicus populations by the dinoflagellate Hematodinium sp. not only provide examples of pathogen-induced mortality, but also have effects on post-harvest products including vivier transport losses and changes in post-mortem degradation leading to earlier organoleptic rejection. Under commercial conditions these effects can be mitigated by post-capture visual screening, but only during the periods of peak patent infection when parasitised animals are visually identifiable. Wider implementation of such mitigating procedures during the harvesting of wild-caught crustaceans will contribute to a more sustainable exploitation of these valuable marine resources.

Although protein metabolism has been studied in fish and other crustaceans, this is the first study to measure protein synthesis rates for Norway lobster Nephrops norvegicus. This research aimed to assess the nutritional status of wild caught Nephrops by measuring tissue rates of protein synthesis and comparing these with rates from fed and starved Nephrops maintained in aquaria. Rates of protein synthesis were measured in the hepatopancreas, gill and tail muscle tissue. A time-course validated the use of a flooding-dose of 3 H phenylalanine to measure protein synthesis in Nephrops and showed that the flooding-dose method is suitable for the study of protein turnover in Nephrops. The relationship between the measured rate of protein synthesis and capacity for protein synthesis (Cs) showed differences between tissues and between nutritional history. Measures of protein metabolism were generally higher in hepatopancreas, then gill and then tail muscle and generally lower in starved animals. Although individual variation meant there were few significant differences in tail muscle values between treatments, RNA concentration was higher in wild-caught than starved and suggested they were not starving. This was supported by hepatopancreas protein synthesis in wild-caught being intermediate between fed and starved, indicating relatively recent feeding had increased hepatopancreas protein synthesis due to increased RNA activity at constant RNA capacity. This study will add to our current but limited understanding of the effects of environmental variations on nutritional status and on protein metabolism and deposition in Nephrops species. Knowledge of the mechanisms enabling their survival is required to understand their ability to adapt to environmental variables.

The present study investigated the existence of inter-individual and within-brood variability in the fatty acid (FA) profile of developing embryos of Nephrops norvegicus. In all surveyed females (n = 5), the quantitatively most important FAs were as follows: 22:6n-3 (20.8 ± 3.9% average of total FA ± standard error), 18:1n-9 (19.5 ± 2.0%), 16:0 (15.2 ± 3.4%), 20:5n-3 (10.2 ± 1.4%), 16:1n-7 (8.9 ± 1.6%), and 18:1n-7 (5.7 ± 1.3%). Differences in FA profiles of embryos in the same clutch were assessed using brooding chamber side (left and right) and pleopod (1st and 2nd, 3rd and 4th, and 5th) as predictive factors. There were no significant differences in the FA composition of embryos sampled from both sides of the brooding chamber in 4 of the 5 surveyed females. However, all females exhibited significant differences in the FA profiles of embryos sampled from different pleopods. Both saturated FA (SFA) and highly unsaturated FA (HUFA) present in developing embryos exhibited marked differences along the breeding chamber. Overall, FA reserves appeared to vary significantly within broods, which can ultimately be reflected on early larval survival. A potential cause for the within-brood variation recorded in the FA profile of developing embryos include (1) differential female investment during ovarian maturation, mainly due to variation in food quality/availability; (2) differential lipid catabolism during the incubation period of developing embryos, as a consequence of embryos position within the female’s brooding chamber; or (3) differential female investment during ovarian maturation amplified by differential lipid catabolism during the incubation period. The authors thank Susana Pereira for their help during the sampling and processing of Norway lobster embryos and Carla Santos during the biochemical analysis. published

Temporal variation in the population abundance of the deep-water rose shrimp, Parapenaeus longirostris (Lucas, 1846) (Decapoda, Penaeidae), and the Norway lobster, Nephrops norvegicus (Linnaeus, 1758) (Decapoda, Nephropidae), in the Tyrrhenian Sea (NW Mediterranean), were evaluated using time-series data (1994–2008) from experimental trawl surveys and commercial landings. The influence of several environmental variables (sea surface temperature, wind-mixing index and NAO index) and fishing effort indices (number of days at sea per month and mean engine power of the trawl fleet) were investigated. The time series were analysed by means of min ⁄ max auto-correlation factor analysis (MAFA) and dynamic factor analysis (DFA). The abundance of P. longirostris showed a clear increasing trend, significantly correlated with the fishing effort index (number of days at sea per month), the sea surface temperature and the wind-mixing index. The temporal variations in the stock of P. longirostris, which has a preference for warm waters, were positively correlated with the rise of the sea surface temperature and the decrease of wind circulation. For N. norvegicus, an increasing trend of landings per unit of effort and recruitment index contrasted with a decreasing trend of relative population abundance (biomass and density indices).

Under prolonged (>24 h) emersion, Norway lobster Nephrops norvegicus changed purineolytic pathways in response to increased levels of circulating ammonia. Haemolymph levels of urea and uric acid more than doubled during emersion, but xanthine oxidase was not detected, even after 72 h emersion. Xanthine dehydrogenase (XDH) was the only form of xanthine oxidoreductase detected, so the metabolic costs of producing uric acid would have been relatively small. Although ammonia, urea, uric acid and XDH all accumulated in the haemolymph during emersion, the relative proportions of ammonia and urea stayed the same at all times, which suggests the presence of enzymes from the uricolyic pathway (e.g. uricase and urease). Supranormal ammonia effluxes occurred almost immediately following re-immersion in amounts that indicate a high degree of hypoxia tolerance under emersion and that this is negatively related with the prevailing temperature. We conclude that N. norvegicus has purineolytic capacity and, under prolonged hypoxia, produces purines de novo as an ammonia-detoxification strategy that has probable survival value for a benthic burrowing species that may experience periods of severe hypoxia.

Pampoulie, C., Skirnisdottir, S., Hauksdottir, S., Olafsson, K., Eiríksson, H., Chosson, V., Hreggvidsson, G. O., Gunnarsson, G. H., and Hjorleifsdottir, S. 2011. A pilot genetic study reveals the absence of spatial genetic structure in Norway lobster (Nephrops norvegicus) on fishing grounds in Icelandic waters. – ICES Journal of Marine Science, 68: 20–25. Stock structure of Norway lobster off southern Iceland was investigated using 12 microsatellite loci. No genetic method detected significant genetic differentiation among the locations sampled, even among Icelandic samples and an out-group from Scotland. Testing the power of resolution of microsatellite loci, the loci and sample sizes used were sufficient to detect significant genetic differentiation with confidence. The lack of genetic structure is discussed in terms of the level of gene flow, recent isolation of populations, and the statistical power of the experimental design.

Five decapod crustacean species were examined for presence of the parasitic dinoflagellate Hematodinium spp. (Alveolata, Syndinea) by morphological methods (colour and pleopod methods) as well as by PCR and nested PCR with Hematodinium-specific primers. Nephrops norvegicus, Pagurus bernhardus and Liocarcinus depurator were sampled by trawling in Danish waters and Chionoecetes opilio and Hyas araneus were sampled by trapping off the west coast of Greenland. The existence of Hematodinium has not previoiusly been documented in Danish waters, but it was detected in all 3 decapod species examined in the present study. Hematodinium sp. was also detected for the first time in H. araneus and the existence of Hematodinium sp. in Greenlandic C. opilio was documented by PCR. Analyses of 26 Hematodinium sp. ITS1 sequences, including sequences from all 5 host species sampled, revealed more than 95% sequence similarity between 24 of the sequences. Two Hematodinium sp. ITS1 sequences from C. opilio were only 81% similar to the 24 other ITS1 sequences. The nested PCR approach resulted in the highest reported percentages of positive samples for Hematodinium sp.in the hosts investigated (between 45 and 87.5%). However, no decapods were found to be infected with Hematodinium sp. based on morphological methods. Consequently, Hematodinium sp. may be more common than previously believed, and, assuming that the DNA found originated from viable and infectious parasite cells, infections may not always be fatal. We suggest that the hosts investigated may have been subject to latent infections that could develop into a fatal disease only if the hosts were physiologically stressed due to other factors.

Madsen, N., and Valentinsson, D. 2010. Use of selective devices in trawls to support recovery of the Kattegat cod stock: a review of experiments and experience. – ICES Journal of Marine Science, 67: 2042–2050. The spawning-stock biomass of cod (Gadus morhua) in the Kattegat area is at a historically low level. Throughout the past decade considerable efforts have been devoted to research on improving both species and size selectivity of the trawls used in the mixed demersal fishery in the area, because this provides a valuable management tool for reducing the bycatch of cod and reducing mortality, and thus helping to rebuild the depleted stock. Gear research in the area has been focused on devices that allow for continued exploitation of the Norway lobster (Nephrops norvegicus) and flatfish, but minimizing the bycatch. We review the results of previous and continuing experiments with various codend mesh sizes, mesh configurations, escape windows, sorting grids, sorting frames, and separator panels, but also changes in whole-trawl designs. Based on our review, we compare and discuss the gear-related technical measures and their effectiveness in maintaining a commercial fishery on viable stocks, yet protecting cod. We discuss the results in relation to changes in legislation and experience with implementation of new selective devices in recent years. We also discuss ways to create stronger incentives for fishers to participate in gear research and to increase acceptance of more selective gears.

Frandsen, R. P., Madsen, N., and Krag, L. A. 2010. Selectivity and escapement behaviour of five commercial fishery species in standard square- and diamond-mesh codends. – ICES Journal of Marine Science, 67: 1721–1731. The Danish fishery for Nephrops (Nephrops norvegicus) is often conducted in a mixed-species setting, characterized by high rates of discards of several target species, including Nephrops and cod (Gadus morhua). Experiments were conducted to investigate and compare the selective properties of a standard 70 mm square-mesh codend (standard SMC) and a standard 90 mm diamond-mesh codend (standard DMC). Selectivity estimates for five commercial species are provided for both codends. The standard SMC yielded higher estimates of length at 50% retention/mesh size (hereafter SF) for Nephrops and roundfish than did the standard DMC, but no effect of codend type on SF was found for plaice (Pleuronectes platessa). Moreover, a novel codend cover design allowed assessment of the preferred direction of escapement in the codend. Whiting (Merlangius merlangus) and Nephrops showed pronounced, but opposite, vertical preference in the direction of escapement, with whiting escaping upwards and Nephrops downwards. A significant (p < 0.05) difference in the direction of escapement between the two codends was found for haddock (Melanogrammus aeglefinus) and whiting. Owing to the relatively small catches, the outcome is probably most applicable to Nephrops-directed fisheries under similar conditions, and caution should be taken not to extrapolate the results to other fisheries.

The effects of four different ante-mortem stressors (exercise, emersion, starvation and a patent infection with the parasite Hematodinium sp.) on post-mortem processes have been investigated in the abdominal muscle of Norway lobster Nephrops norvegicus by measuring changes in the pH, the levels of glycogen, l-lactate, arginine phosphate, ATP, ADP, AMP, IMP, HxR, Hx and the adenylate energy charge (AEC) over a time course of 24 h with samples being taken at 0, 3, 6, 12 and 24 h. The acute stresses of intense exercise and 2 h emersion resulted in a premature onset of anaerobic glycolysis, leading both to an enhanced glycogen depletion rate and an early accumulation of l-lactate. The chronic stressors, starvation and parasite infection, resulted in a complete ante-mortem depletion of muscle glycogen and consequently the failure of post-mortem glycolytic fermentation. Post-mortem pH and ATP inter-conversion were significantly altered in chronically stressed animals. Ante-mortem, a rapid, almost compl...

10 páginas, 2 figuras, 2 tablas., The day–night cycle is one of the strongest geophysical cycles modulating species’ behavioral rhythms. However, in deep-water continental margins, where light intensity decreases over depth, interspecific competition may alter behavioral responses to day–night cycles. The burrowing decapod crustacean Nephrops norvegicus is a large-size predator in benthic communities, exerting despotic territorial behavior. In this study, we analysed how the effect of light intensity cycles on decapod behavioral rhythms is reduced as one moves from shelves to slopes. In the Western Mediterranean, the predatory behavior and interspecific competition for substrate use of Nephrops increases moving from the shelf (100–110 m) to the slope (400–430 m). Vector fitting and generalized additive models were used to assess the effect of light intensity and behavioral rhythms of N. norvegicus on the temporal variation of prey decapods co-occurring in trawl tow catches carried out on the shelf and the slope during October 1999 and June 2000. The combination of diel variations in light intensity and N. norvegicus abundance influences the activity rhythms of prey decapods in a depth- and seasonal-dependent manner. Light modulation is stronger on the shelf and weaker on the slope, where Nephrops population size is greater. Although present regression analysis does not necessarily imply a direct cause– effect relationship between rhythms of predators and prey, we suggest that Nephrops alters the temporal patterning in the behavior of its prey on the slope, where light intensity is reduced. This alteration is stronger in endobenthic species than in benthopelagic species; the former rely on bottom substrate for the expression of behavioral rhythms, experiencing stronger interspecific competitions with Nephrops at time of activity., We acknowledge Prof. F. Sarda` (ICM-CSIC), head of the project NERIT (MAR98-0935) funded by the Spanish CICYT. J. Aguzzi is a postdoctoral fellow in the ‘Juan de la Cierva’ Program (Spanish Ministry of Education and Science)

The effects of capture method (creel and trawl) and trawling time (15, 60 and 150 min) were assessed in Norway lobsters by measuring stress-related metabolites together with nucleotide breakdown products. Furthermore, mechanical damage was scored in the animals captured by trawl. Capture method had a clear impact on the nucleotide profile in the Norway lobster muscle. In rested and creel-caught animals the main nucleotide was ATP, while in trawled animals the main nucleotide was AMP. According to these results the Adenylate Energy Charge (AEC) was lower in trawled animals compared with creel-caught animals, while trawling time did not affect AEC levels significantly. Stress-related and anaerobic metabolites together with muscle pH indicated that trawled animals, even at the shortest time tested, were using anaerobic metabolism. In the haemolymph, l-lactate increased with a delay compared with muscle, suggesting that the concentration of l-lactate in the muscle provides a more immediate measure of...

The reproductive biology of female Norway lobster Nephrops norvegicus was studied throughout an annual cycle from January to December 2007 in Pagasitikos Gulf, a large semi-enclosed Gulf in the central west Aegean Sea, in Greece. Six ovarian maturation stages were described to follow gonadal development, based on the combined external observation and histological examination of the ovary. Reproduction showed clear seasonality both in terms of ovarian maturation and brooding period. The proportion of fully mature females in the catch increased from January to the summer months with a peak in June. The species has a protracted brooding period that peaks in November and December, while the release of eggs from females' pleopods occurs from January to March. The size at which 50% of females reached sexual maturity was estimated, using a logistic model, to be 28.1 mm of carapace length. The undiscovered reproductive dynamics will be valuable for optimizing population models and management strategies for this important fishery resource.

Campbell, N., Allan, L., Weetman, A., and Dobby, H. 2009. Investigating the link between Nephrops norvegicus burrow density and sediment composition in Scottish waters. – ICES Journal of Marine Science, 66: 2052–2059. Nephrops norvegicus is a burrowing decapod, found in the North Atlantic and Mediterranean Sea at depths of 10–1200 m, and currently the most valuable species taken by the commercial fishing industry in Scotland. It constructs and inhabits extensive burrow complexes in suitable muddy sediments. Owing to its variable emergence patterns, catch rates from traditional trawl surveys are not considered a good indicator of population size. Nephrops populations around Scotland are assessed using an underwater television (UWTV) survey method. Sediment samples are collected at the end of each UWTV deployment. This study focuses on two areas off the coast of Scotland and investigates the accuracy of the sediment maps used for assessment purposes, and the relationship between Nephrops burrow density and sediment composition, over the period 2002–2007. Nephrops have a stock-specific relationship with the sediment they inhabit, which retains the same form through fluctuations in population size.

It was found that the striated muscle of the Norway lobster ( Nephrops norvegicus ) does not exhibit the rigor mortis state otherwise typical for this type of muscle. This absence of rigor was investigated, concentrating on changes in the structure, ultrastructure and post-mortem biochemistry of the muscle. Samples were initially fixed for light and electron microscopy at the time of death and at different times post-mortem (3, 6, 12 and 24 h). Protein extracts were obtained in parallel to compare the banding patterns of the myofibrillar proteins using SDS-PAGE. A Western blot was applied to elucidate if myosin – a representative major myofibrillar protein – was degraded post-mortem. And finally, ATP levels in the muscle were analyzed using HPLC. Using TEM imaging it was found that between 12 and 24 h post-mortem at a storage temperature of 10 °C, when rigor mortis should set in (according to the muscular ATP concentrations), an extensive, but rather specific breakdown of myofibrillar proteins occurred. The Z-disks were degraded and the myofibrillar structure was lost. SDS-PAGE and Western blot clearly demonstrated the post-mortem breakdown of myosin. The nature of the observed protein breakdown seems to impede rigor mortis in some way by the activation of at least one of the several proteolytic systems (cathepsins, calpains and others) found in vertebrates and invertebrates. It is speculated that the proteolysis simply overtakes the rigor -inducing post-mortem changes.

Live Norway lobsters ( Nephrops norvegicus L.) were trawled at depths of 30 to 55 m off the coast of Jutland (Denmark) in late winter (March) and in summer (August) in 2006. Water temperatures at the bottom and surface of the sea were 7 °C and 2 °C during the winter, and 12 °C and 21 °C in the summer, respectively. The recovery of specific physiological and metabolic variables from the intense stresses associated with capture (trawling and air-exposure during sorting) was followed in seawater at 5 °C in winter or 18 °C in summer. Recovery was compared in lobsters held individually in two different live-storage positions, either resting vertically on the tail or sitting horizontally. In winter, many animals were alive when brought on board and approximately 86% were still alive at the end of experimentation (96 h). In summer very few animals were alive when brought on board and, of these, approximately 95% were dead at 24 h. When compared with values measured in laboratory controls, the stresses of capture elicited very high haemolymph lactate contents in both seasons, although levels recovered within 24 h. Trawling also caused very high haemolymph glucose concentrations, which differed with season. In winter, haemolymph glucose was elevated for 24 h to levels significantly higher than in summer. In summer, glucose had returned to control levels by 4 h. At 4 h after trawling, haemolymph O 2 status was not markedly influenced in either season, but there were significant disturbances of acid-base status. In winter, a potential metabolic lactic acidosis was compensated by a marked respiratory alkalosis, with significantly increased haemolymph pH and decreased CO 2 total content and partial pressure. These effects disappeared gradually over 96 h. Summer lobsters showed combined metabolic and respiratory acidosis at 4 h, although this had recovered to control values in the small number of survivors sampled at 24 h. The capture stresses elicited very high haemolymph crustacean hyperglycaemic hormone (CHH) titres, significantly higher in summer than in winter. In winter, CHH titre had declined significantly at 24 h, whereas it exhibited a further significant increase at 24 h in summer. Live-storage position had no significant effect on survival or recovery from capture stresses in either season. The results demonstrate that Nephrops were much more stressed by trawling at high summer temperatures and had difficulty recovering from this, with pronounced negative effects on their survival, irrespective of their live-storage position.

Campbell, N., Dobby, H., and Bailey, N. 2009. Investigating and mitigating uncertainties in the assessment of Scottish Nephrops norvegicus populations using simulated underwater television data. – ICES Journal of Marine Science, 66: 646–655. Nephrops norvegicus is a commercially significant decapod crustacean that excavates and inhabits burrows in muddy sediments throughout the Northeast Atlantic and Mediterranean Sea. Because of its variable emergence behaviour, traditional surveys are considered a poor indicator of the status of its populations, and underwater television (TV) survey methods have been developed. The approach involves towing a TV camera over patches of muddy sediment and counting the number of Nephrops burrow complexes within a known area. Assuming a 1:1 rate of occupancy, the average population density can be estimated. This is raised to the known area of suitable sediment to give a measure of population size. Recently, underwater TV surveys have been used to provide absolute measures of abundance for a number of Nephrops stocks in the North Sea and Northeast Atlantic. It is therefore imperative to identify, quantify, and control for uncertainties in this process. Previous workers have suggested that visual recognition of Nephrops burrows and “edge effects”, where single openings of burrow complexes at the sides of the viewed transect are counted, are important sources of uncertainty. This study shows edge effects to be responsible for an overestimation of population size of between 4 and 55%, depending on the width of the field of view and the mean size of the burrow complex. This overestimation is countered to some extent by variability in burrow entrance structure, which leads to Nephrops burrows going unrecognized. The scales of these errors are discussed in relation to observed sediment softness, sediment distribution, and burrow dimensions from sites around Scotland.

Milligan, R. J., Albalat, A., Atkinson, R. J. A., and Neil, D. M. 2009. The effects of trawling on the physical condition of the Norway lobster Nephrops norvegicus in relation to seasonal cycles in the Clyde Sea area. – ICES Journal of Marine Science, 66: 488–494. The fishery for Norway lobster, Nephrops norvegicus, is the most valuable in Scotland, but few studies have examined the physical condition of the animals trawled. This study aimed to determine the extent of physical damage caused by trawling to Nephrops in the Clyde Sea area in relation to trawl duration, sex, size, and moult stage. Longer trawls (2.5–4 h) corresponded to increased damage in “hard” (intermoult) Nephrops compared with short (1 h) or very short (15 min) trawls, but there was no correlation in “soft” (late intermoult or recently moulted) or “jelly” (immediate post-moult) Nephrops. This effect appeared to be limited to Nephrops with a carapace length (CL) of 20.0–29.9 mm. Seasonal effects were also observed, with numbers of jelly Nephrops highest in May 2006, corresponding to a peak in female prevalence in the catches, an increase in the mean CL of females, and greater damage in females. The proportion of females was higher than males from May to September 2006, and it is suggested that this corresponds to female emergence patterns. As quality will be low, it may be pertinent to avoid fishing during the peak emergence period to maximize the quality and profitability of catches.

Ungfors, A., McKeown, N. J., Shaw, P. W., and André, C. 2009. Lack of spatial genetic variation in the edible crab (Cancer pagurus) in the Kattegat–Skagerrak area. – ICES Journal of Marine Science, 66: 462–469. The stock structure of the edible crab (Cancer pagurus L.) in the Kattegat and Skagerrak was investigated using eight microsatellite DNA loci. Replicate samples, collected 4–6 years apart, were derived from the Kattegat (Grove Bank, 57°N) and the Skagerrak (Lunneviken, 59°N), plus a geographical outgroup sample from the Norwegian Sea (Midsund, 62°N). Genetic differentiation among samples, estimated as global FST = 0.002, was significant (p = 0.03) when the statistical test was based on allele frequencies, but not when based on genotype frequencies. Moreover, all single- and multilocus pairwise tests between samples were non-significant. An analysis of molecular variance, AMOVA, did not reveal significant differentiation between spatial (Kattegat vs. Skagerrak) or temporal (2001/2002 vs. 2006/2007) groups of samples. Power analysis suggested that the loci and sample sizes employed conferred a power of >90% of detecting even low (true FST = 0.002) levels of population structure. Low spatial and temporal genetic structure might be explained by either or both of (i) high levels of contemporary gene flow in the area attributable to adult migration or larval dispersal or both factors taken together, and (ii) patterns of historical gene flow persisting among recently founded large populations.

The effects of prolonged emersion (24, 48 and 72 h) and subsequent re-immersion on Nephrops norvegicus (L.) held at 5 degrees C were assessed using an index of physical quality criteria and a suite of haemolymph constituent assays. Collectively, these showed classical hypoxia-induced changes over 48 h of emersion, but, subsequently, between 48 and 72 h emersion, physical activity, haemolymph pH and circulating levels of urate, free amino acids and major ions all returned to normal (control) levels, and L-lactate levels had started to decrease towards control levels. These patterns of changes differed from that of the haemolymph total ammonia levels which continued to increase linearly throughout emersion. N. norvegicus appeared to partially compensate for the post- 48 h emersion increased levels by increasing the production, and hence relative proportions, of other less toxic nitrogenous metabolites. The data replicated that of preliminary trials. Working on the presumption that such events could occur only in the presence of oxygen, possible sources of such oxygen under prolonged hypoxia are discussed. The low holding temperature appears to be the key to prolonged survival of N. norvegicus, and the switch from anaerobic to aerobic respiration itself appears to be a function of a preceding, prolonged period of hypoxia. The ecological and commercial implications for a burrow-dwelling, benthic animal that may experience episodic periods of hypoxia and which forms a highly important proportion of the value of total UK commercial landings are discussed.

Smith, I. P., and Jensen, A. C. 2008. Dynamics of closed areas in Norway lobster fisheries. – ICES Journal of Marine Science, 65: 1600–1609. A dynamic, age-structured population model was developed to investigate the potential effects of introducing a closed area to a fishery for a species with limited adult mobility and planktonic dispersal of larvae, using biological and fishery information from a Norway lobster fishery in eastern Scotland. Simulated closure of part of the fishing grounds led to a long-term increase in total biomass and recruitment to the fished zone, but the larval subsidy did not compensate for the loss of fishing ground, and fishery yield was reduced under all modelled combinations of closed-area size and prior fishing effort. Concentration of effort in the fished zone and increased recruitment there led to reduced average size, and therefore value, of animals in the catch, as well as increased destruction of biomass by discarding undersized lobsters. Implementation of a closed area also led to oscillations in stock biomass, recruitment, and yield over several years after the closure, particularly with large closed areas and high fishing effort.

The use of image-based technologies has gained increasing importance in marine research, particularly in benthic habitat classification and the assessment of epibenthic commercial species. A common application that has now entered into the routine of a number of northeastern Atlantic research institutes and in the Mediterranean (on an irregular basis) is fishery-independent estimation of Norway lobster Nephrops norvegicus abundance. Typically, the experimental set-up consists of a video camera mounted on a sledge towed from a research vessel during targeted surveys. Targeted surveys produce superior images; however, fishing operations cannot be carried out simultaneously, which limits the amount of information collected. During a research cruise testing the use of by-catch reduction devices (BRD) to optimise the fishing pattern of Norway lobster, an underwater video camera was hung from the trawl headline, angled down in the tow direction to register ground images. We evaluated the potential usefulness of this set-up as an alternative to traditional methods for the study of benthic habitats and pre- sent a case study of the Norway lobster. A preliminary estimate of burrow entrance density (2.1 m -2 ) in Portuguese waters was obtained by superimposing a measuring grid over individual image frames. The combined approach (video recording while trawling) also allowed a first estimate of the survey trawl efficiency (0.46). The advantages (e.g. simultaneous image and lobster samples) and disadvantages (e.g. low quality image due to the high trawling speed and mud clouds) of the experimental set-up are discussed, concluding by its practicability. However, its application to Norway lobster density estimation as an alternative to current procedures will require further development.

A set of simulations using a validated and realistic parameterization of a numerical model was conducted for the south and southwest Portuguese regions as an attempt to understand larval dispersal patterns in the Norway lobster ( Nephrops norvegicus ). Larvae were introduced in the model as Lagrangian particles with five different behavioural scenarios concerning their ability to migrate vertically. Growth rate was temperature dependent and the larvae were tracked individually. The end point of the simulations was the position of the larvae when they reached competency at age 1. Age 1.25 was also considered to simulate a possible delay in settling due to lack of an appropriate substrate. The results showed that the majority of the larvae reached age 1 near the hatching area along the southern shelf, while low exchange of larvae between the south and the west coasts was observed, especially for behavioural scenarios where larvae remained in relatively shallow waters. Scenarios where larvae performed diurnal vertical migration and delayed settlement until age 1.25 indicated a tendency for westward motion because of interactions with the Mediterranean undercurrent. Self-recruitment to the Algarve stock was estimated at 0.2% to 0.5%, raising the concern that this stock may be experiencing recruitment limitation.

Immune defence in creel-caught and trawled Nephrops norvegicus was investigated to assess a possible relationship between phenoloxidase (PO) activation and the total haemocyte count (THC). Capture, capture method and emersion evoked physiological and immunological responses that may have implications for the ability of N. norvegicus to survive the effects of such stressors. Haemolymph THC was always negatively related to PO activity in the trawled samples, suggesting a decreased level of the plasma serine proteinase inhibitors which reportedly regulate the ProPO system (Le Moullac et al. 1998; Fish shellfish Immunol 8:621-629). In contrast, creel-caught samples showed increased levels of both PO and THC (cf. control N. norvegicus), after a 12 h emersion period. Trawling and emersion evoked progressive and significant increases (p < 0.05) in the mean levels of haemolymph L-lactate, glucose and total ammonia. The evidence of overt activity and measured haemolymph parameters suggest that creel fishing yields N. norvegicus that are more likely to survive post-harvest treatments than those that are trawled.

The environmental impact of 'ghost fishing' has been identified as a major issue in the capture fishing industry. The present study assesses the potential for ghost fishing in the creel (baited trap) fishery for Norway lobster Nephrops norvegicus, one of the most valuable fished species in European waters. Baited creels were deployed and monitored at a shallow and a deep site for 363 and 217 d, respectively. Catch was counted at regular intervals by SCUBA diving at the shallow site and by periodically hauling creels at the deepwater site. Both trials showed that most captured species were able to escape from the creels, with only N. norvegicus being trapped for long periods of time, suggesting that creels are very selective for the target species. Dead target or non-target species within creels appeared to be ineffective at attracting additional N. norvegicus into the creels. It was concluded that, following the initial attraction to creels, once all the bait has been consumed, lost creels will cease to fish. The main reasons for the low ghost fishing performance of N. norvegicus creels may be the design of the creel itself (which allows non-target species to escape relatively eas- ily), the behaviour of N. norvegicus restricting the number of animals entering the creels once the bait has been consumed, and the ability of N. norvegicus to survive for long periods of time once caught.