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Recent improved practices in the trawl fishery for Norway lobsters ( Nephrops norvegicus ) have made it possible to increase the proportion of trawl-caught lobsters that can be transported alive successfully. A major contributor to this has been the introduction of on-board seawater tanks, which allow for the recovery of animals immediately after they have been landed from the net. In this study, we have validated a vigour index that could be used both by fisheries scientists and by the industry dealing with live-traded Nephrops, allowing identification of the proportion of trawl-caught lobsters that fail to recover following capture and are not in a condition to survive live transportation. Results indicate that the process of visual selection into one of four possible vigour categories reflects with good accuracy the underlying physiological state of the animals, as assessed by the level of adenylate 5′ –triphosphate in the tail muscles, by the proportions of other nucleotides as expressed in the Adenylate Energy Charge, and by the amount of intra-muscular l -lactate present. The vigour index also correlates well with their subsequent survival potential in a semi-dry transport system. [ABSTRACT FROM AUTHOR]

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 quadrig 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. [ABSTRACT FROM AUTHOR]

Due to generally high discard rates in Norway lobster ( Nephrops norvegicus ) fisheries, a discard ban coming up and to the cod recovery plan in several areas, selective sorting grids have been tested in many areas and are specified by legislation for use in the Kattegat and Skagerrak area bordering Norway, Denmark and Sweden. Grids are very selective, but they can lead to loss of landable Norway lobster and valuable fish species. To improve retention of these species, we developed three new grids using made by polyurethane to make them flexible: One grid had horizontal bars, one had vertical bars, and one had vertical bars and a guiding funnel in front of the grid. Four unselective net bags were used to collect the catch escaping through different parts of the grid or escaping without passing through the grid. Water flow around the grid bars was measured in a flume tank. The three grids were tested from a commercial trawler in the Kattegat and Skagerrak area. Underwater filming was conducted to assess grid performance and fish behavior. Results showed that a bottom hole in the lower part of the grid allowed species in the lower part of the gear to pass and retained in the bag behind the hole. More flatfish passed the grid with horizontal bars compared to that with vertical bars, but the retention rate was still low. Use of the guiding funnel increased the contact with the grid considerably for both target and unwanted species. In all three grid designs, there were losses of Norway lobster above minimum landing size. [ABSTRACT FROM AUTHOR]

Creel catch performance is known to be affected by the soak time in many fisheries. If creels maintained their efficiency over longer periods, increase in soak time should lead to proportional increase in catch quantity. However, the exact shape of this relationship is unknown for creel fisheries targeting Norway lobster (Nephrops norvegicus). If it was known fishermen could adjust their fishing strategy accordingly and maximize their net earnings. We compared catch performance of creels targeting Norway lobster soaked for one and two days in the Adriatic Sea. Results were obtained for three crustacean species, Norway lobster (N. norvegicus), mantis shrimp (Squilla mantis), and blue-leg swimming crab (Liocarcinus depurator) and two fish species, poor cod (Trisopterus minutus) and blotched picarel (Spicara flexuosa). Doubling the soak time from one to two days did not double the catches and for Norway lobster no increase was found. For the other crustaceans, a slight but not significant increase was estimated. Catches of blotched picarel were significantly lower for the longer soak time, while the results were inconclusive for the poor cod. [ABSTRACT FROM AUTHOR]

The aim of this research is to study the seasonal histological changes in the digestive gland of males and females Nephrops norvegicus at the Pagasitikos Gulf. The food availability in Pagasitikos Gulf varies and depends on the seasonality, physicochemical conditions and diversification of organic material. After obtaining histological sections, the size of tubules, their lumens and the R-, F- and B-cells were calculated in March and May. A special image analysis algorithm was used that can automatically calculate both the above area ratios using digestive gland histological sections. Both male and female, which were sampled in May, had a larger density of lipid droplets than N. norvegicus sampled in March. However, females sampled in May had more lipid droplets per tubule and a smaller F-cell-to-tubule ratio than males, which indicated that the intensive feeding period had started for reproduction in the females. The digestive gland can be used as a nutritional indicator to assess the nutritional status of Nephrops stocks and to assist with the management of the Nephrops wild stocks by proposing a seasonal fishery management plan to improve the sustainability of the stocks. [ABSTRACT FROM AUTHOR]

The Norway lobster, Nephrops norvegicus, can be captured by haul nets only during the emergence from its burrow. In the last few decades, an extensive field research revealed distinct diel (24-h–based) catchability patterns at different depths. Laboratory experiments suggested that burrow emergence (used as a proxy of catchability) is endogenously controlled via a circadian system. Results were usually presented in terms of mean effects without a quantification of inter-individual variability and arrhythmia. Here, we studied the burrow emergence of 52 adult Nephrops by an infrared actograph endowed with an artificial burrow. Animals were exposed to 12-12 h light-darkness cycle, simulating photic condition of the lower shelf. Forty-five animals showed rhythmic emergence (87%), while seven were arrhythmic (13%). Rhythmic animals were clustered according to their timing of emergence: 54% at dusk and 4% at dawn. Moreover, other animals showed fully diurnal or nocturnal emergence (10% and 19%, respectively). The comparison of our results with those derived from temporally scheduled trawling indicates that bimodal catch patterns observed in shelf populations are poorly observed during individual experiments in the laboratory, where the same light conditions are simulated. Nephrops burrow emergence seems to be the result of a mixed endogenous-exogenous control, while arrhythmia could also be present in the wild.

Radio frequency identification (RFID) devices are currently used to quantify several traits of animal behaviour with potential applications for the study of marine organisms. To date, behavioural studies with marine organisms are rare because of the technical difficulty of propagating radio waves within the saltwater medium. We present a novel RFID tracking system to study the burrowing behaviour of a valuable fishery resource, the Norway lobster (Nephrops norvegicus L.). The system consists of a network of six controllers, each handling a group of seven antennas. That network was placed below a microcosm tank that recreated important features typical of Nephrops’ grounds, such as the presence of multiple burrows. The animals carried a passive transponder attached to their telson, operating at 13.56 MHz. The tracking system was implemented to concurrently report the behaviour of up to three individuals, in terms of their travelled distances in a specified unit of time and their preferential positioning within the antenna network. To do so, the controllers worked in parallel to send the antenna data to a computer via a USB connection. The tracking accuracy of the system was evaluated by concurrently recording the animals’ behaviour with automated video imaging. During the two experiments, each lasting approximately one week, two different groups of three animals each showed a variable burrow occupancy and a nocturnal displacement under a standard photoperiod regime (12 h light:12 h dark), measured using the RFID method. Similar results were obtained with the video imaging. Our implemented RFID system was therefore capable of efficiently tracking the tested organisms and has a good potential for use on a wide variety of other marine organisms of commercial, aquaculture, and ecological interest.

There is growing interest in developing automated, non-invasive techniques for long-lasting, laboratory-based monitoring of behaviour in organisms from deep-water continental margins which are of ecological and commercial importance. We monitored the burrow emergence rhythms in the Norway lobster, Nephrops norvegicus, which included: a) characterising the regulation of behavioural activity outside the burrow under monochromatic blue light-darkness (LD) cycles of 0.1 lx, recreating slope photic conditions (i.e. 200-300 m depth) and constant darkness (DD), which is necessary for the study of the circadian system; b) testing the performance of a newly designed digital video-image analysis system for tracking locomotor activity. We used infrared USB web cameras and customised software (in Matlab 7.1) to acquire and process digital frames of eight animals at a rate of one frame per minute under consecutive photoperiod stages for nine days each: LD, DD, and LD (subdivided into two stages, LD1 and LD2, for analysis purposes). The automated analysis allowed the production of time series of locomotor activity based on movements of the animals’ centroids. Data were studied with periodogram, waveform, and Fourier analyses. For the first time, we report robust diurnal burrow emergence rhythms during the LD period, which became weak in DD. Our results fit with field data accounting for midday peaks in catches at the depth of slopes. The comparison of the present locomotor pattern with those recorded at different light intensities clarifies the regulation of the clock of N. norvegicus at different depths.

In the UK, the Norway lobster (Nephrops norvegicus) supports its most important shellfish fishery. Nephrops are sold either whole, or as "tails-only" for the scampi trade. In the "tailing" process, the "head" (cephalothorax) is discarded as waste. A smaller crustacean species, the Antarctic krill Euphasia superba, represents an economically valuable industry, as its extractable oil is sold as a human dietary supplement. The aim of this study was to determine the amount and composition of the oil contained in discarded Nephrops heads and to compare its composition to the oil extracted from krill. Differences due to Geographical variation and seasonal patterns in the amount and composition of lipid were also noted. Results indicated that Nephrops head waste samples collected from more southern locations in Scotland (Clyde Sea area) contained higher levels of oil when compared to samples collected from northern locations in Iceland. Moreover, seasonal differences within the Clyde Sea area in Scotland were also observed, with oil extracted from Nephrops head waste peaking at around 11.5% during the summer months when larger and more mature females were caught by trawl. At this time of the year, the valuable fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) accounted for around 23% of the total fatty acid content in oil extracted from Nephrops head waste. A seasonal effect on EPA content was found, with higher levels obtained in the summer, while no trend was found in DHA percentages. Finally, oil from Nephrops head waste contained a higher proportion of EPA and DHA than krill oil but these fatty acids were more abundantly linked to the neutral lipids rather to than polar lipids. The characterization of lipid that could be extracted from Nephrops head waste should be seen as a first step for the commercial use of a valuable resource currently wasted. This approach is extremely relevant given the current limited supply of EPA and DHA and changes in the Common Fisheries Policy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Microplastic represents a rising proportion of marine litter and is widely distributed throughout a range of marine habitats. Correspondingly, the number of reports of species containing microplastics increases annually. Nephrops norvegicus in the Firth of Clyde have previously been shown to retain large aggregations of microplastic fibres. The potential for N. norvegicus to retain plastic over an extended time period increases the likelihood of any associated negative impacts to the individual. This study represents the longest observation of the impacts of microplastic retention in invertebrates. We exposed N. norvegicus to plastic over eight months to determine the impacts of extended exposure. Over this period we compared the feeding rate, body mass, and nutritional state of plastic-fed N. norvegicus to that of fed and starved control groups. Following the experimental period, the plastic-fed langoustine contained microplastic aggregations comparable to those of small individuals from the Clyde Sea Area. Comparisons between fed, unfed and plastic-fed individuals indicated a reduction in feeding rate, body mass, and metabolic rate as well as catabolism of stored lipids in plastic contaminated animals. We conclude that N. norvegicus exposed to high levels of environmental microplastic pollution may experience reduced nutrient availability. This can result in reduced population stability and may affect the viability of local fisheries. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 maleN. norvegicuswere taken for femaleN. norvegicusunder 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. [ABSTRACT FROM AUTHOR]

Sulfated glycosaminoglycans (SGNL) were extracted for the first time from Norway lobster ( Nephrops norvegicus ) shell. The monosaccharide composition analysed by GC/MS revealed the presence of galacturonic acid, glucuronic acid, N -acetylgalactosamine and N -acetylglucosamine. The analysis of SGNL with acetate cellulose electrophoresis in Zn-acetate revealed the presence of heparan sulfate (HS) and dermatan sulfate (DS). SGNL were evaluated for their anticoagulant activities using activated partial thromboplastin time (aPTT), thrombin time (TT) and prothrombine time (PT) tests. After 21 h incubation, HCT116 cell proliferation was inhibited ( p < 0.05) between 39.7 and 54.8% at 1.5–7.5 mg/mL of SGNL. SGNL don’t show hemolytic activity towards bovine erythrocytes and no cytotoxicity against the normal lymphocytes. The antiproliferative efficacy of these lobster glycosaminoglycans were probably related with the higher sulfate content. SGNL demonstrated promising antiproliferative and anticoagulant potential, which may be used as a novel, effective and promising antithrombotic agent. [ABSTRACT FROM AUTHOR]

One of the most effective ways to alter catch and length compositions in trawls is to adjust the mesh size or add selective devices such as sorting grids and selective netting panels. These changes are often introduced into the fishery in a top down manner whereby fishermen are forced to comply with specific legislation. However, fishermen have also introduced gear modifications that have contributed to improving species selectivity in trawls. One of the simplest and most effective modifications that came from industry was the development and introduction of twin and multi-rig trawls. Here we analyse catch rates of four target species, Norway lobster ( Nephrops norvegicus ), cod ( Gadus morhua ), plaice ( Pleuronectes platessa ) and haddock ( Melanogrammus aeglefinus ), to try and understand how the use of multi-rig trawls have altered catch rates within the Danish demersal trawl fishery over the last 16 years (1997–2012). Results showed that catch rates of Nephrops in multi-rig trawls were significantly higher (1.89–2.03) than those in single trawls. For cod, haddock and plaice there was no significant effect of gear type. The results are discussed in relation to the Common Fisheries Policy reform and the increasing importance of industry introduced gear modifications. [ABSTRACT FROM AUTHOR]

The effects of trawling on cardiac rhythmicity of Nephrops norvegicus (L.) are still mostly unknown. Ultradian rhythms reported in previous studies may result from trawling capture stress, thus disappearing following acclimatisation to laboratory conditions. To test this hypothesis, 34 time series of cardiac activity data recorded in constant darkness were studied by Fourier analysis. Spectral decomposition of time series was obtained by defining the fundamental or circadian harmonic (CH) in 24-h together with 9 submultiples of this period. The power content (PC) of each harmonic was estimated in data segments of 24-h duration (days), giving graphic matrices of PC values over consecutive days. Values of PC for 9 submultiples were summed and studied in a block named ultradian band (UB). The modification in the PC of the CH and of the UB was evaluated during laboratory acclimatisation. A significant increase in the PC of the circadian harmonic component (CH) over consecutive days of testing was observed. These findings suggest that, rather than being a product of dim light environmental fluctuations experienced by the animals from the deep waters of the continental slope, ultradian periodicity could well be caused by the stress of capture.

The main characteristics concerning distribution, size structure and total mortality of two of the most important decapod crustaceans of commercial interest in the Mediterranean Sea, Nephrops norvegicus and Parapenaeus longirostris, are studied along the European Mediterranean coasts. The study is based on data collected during a series of six trawl surveys performed in spring from 1994 to 1999 from the Gibraltar Straits to the Aegean Sea. The population size structure identified in the different geographical sectors is analysed taking into account two bathymetric sectors: continental shelf and upper slope. Differences in N. norvegicus population demographic structure among geographical sectors, as well as in total mortality, appear to be highly related to different exploitation levels. Size structure in P. longirostris also shows a great heterogeneity throughout the different geographical sectors. Considering that both species are heavily exploited all along the studied area, the observed differences can be interpreted as different responses to exploitation related to the widely differing life history characteristics of the mentioned species. In fact, N. norvegicus is a long-lived, benthic, burrowing species with low growth and mortality rates, and P. longirostris an epibenthic short-lived species characterised by higher rates of growth and mortality.

Anthropogenic pollution is considered one of the main threats to the marine environment, and there is an imperious need to assess its potential impact on ecologically and economically relevant species. This study characterises plastic ingestion and tissue levels of potentially toxic metallic elements in Nephrops norvegicus and their simultaneous levels in abiotic compartments from three locations of the Catalan coast (NW Mediterranean Sea). A multidisciplinary assessment of the health condition of N. norvegicus through condition indices, enzymatic biomarkers and histological techniques is provided, and its relationship with anthropogenic pollutant levels explored. Plastic fibres were commonly found in stomachs of N. norvegicus (85% of the individuals), with higher abundances (13 ± 21 fibres · ind−1) in specimens captured close to Barcelona. The presence of long synthetic fibres in near-bottom waters, as well as the mirroring trends in abundance among locations for water and ingested plastics, suggest that uptake from water may be occurring potentially through suspension feeding. The spatial variability in the levels of metallic elements in N. norvegicus was poorly correlated to the variability in sediments. In any case, present levels in abdominal muscle are considered safe for human consumption. Levels of ingested plastics only showed significant, yet weak, correlations with glutathione S -transferase and catalase activities. However, no other health parameter analysed showed any trend potentially associated to anthropogenic pollutant levels. Neither the condition indices nor the histopathological assessment evidenced any signs of pathologic conditions affecting N. norvegicus. Thus, it was concluded that presently there is no evidence of a negative impact of the studied pollutants on the health condition of N. norvegicus in the studied grounds. [Display omitted] • Nephrops norvegicus ingested between 5 and 13 synthetic fibres on average. • Metallic elements are below levels of attention for human consumption. • No correlations between levels of pollutants and health markers were observed. • Analysed individuals are considered in overall good health status. [ABSTRACT FROM AUTHOR]

Estimates of gut evacuation rates of Nephrops norvegicus (Linnaeus, 1758) (Crustacea, Decapoda) were obtained during laboratory and field experiments. Individuals were collected off the south coast of Portugal in December 1997 and July 1998. Gut evacuation rates (R.h-1) were calculated from the slope of the regression of the natural logarithm of dry stomach content weight versus time, using data obtained by the serial slaughter method. The values obtained during laboratory (R=0.172 h-1) and field experiments (R=0.177 h-1) are compared with gut evacuation rates reported for other marine organisms. The results obtained for both experiments are within the range of the values in the literature, even in the case in which different methodologies were used.

The relationships between fecundity and egg volume of Norway lobster (Nephrops norvegicus) inhabiting three different depth ranges (200-300, 350-450, and 500-550 m) in the North Tyrrhenian Sea (western Mediterranean) were compared. Fecundity was not dependent on depth and egg volume did not vary with female size. The egg volume of females collected in the shallowest areas (200-450 m) was instead significantly larger than that collected in deeper waters (500-550 m). Possible explanations for this fact are examined.

Research into the influence of environmental variables on the behaviour of Norway lobster ( Nephrops norvegicus), and hence catch rates, dates back to the 1960s (e.g., Höglund and Dybern, Diurnal and seasonal variations in the catch-composition of Nephrops norvegicus (L.) at the Swedish west coast. ICES CM 1965/I46; Simpson, Variations in the catches of Nephrops norvegicus at different times of day and night. Rapport et Proés-verbaux des Réunions Conseil permanent international pour 1'Exploration de la Mer 156:186). However, the use of fishery-dependent data in identifying influential factors is relatively limited and only includes a number of papers on a limited dataset (e.g., Redant and De Clark, Diurnal variations in CPUE and length composition of the catches in a Nephrops directed fishery in the Central North Sea. ICES CM 1984/K:3; Maynou and Sardà, Influence of environmental factors on commercial trawl catches of Nephrops norvegicus (L.). ICES J. Mar. Sci. 58:1318). Here, we aimed to dissociate environmental variability in Norway lobster catches to improve resource exploitation efficiency within the Skagerrak and Kattegat trawl fisheries by utilising data collected as part of an extensive at-sea-sampling programme spanning 16 years. Catch rates were modelled using Generalized Additive Mixed Models ( GAMMs) and considered a range of response variables, including depth, temperature, current speed, season, moon phase and time of day. The results obtained herein showed that time of day, season, depth, temperature, year, trawl type and location all significantly affect catch rates of Nephrops. [ABSTRACT FROM AUTHOR]

The age information of commercially important species is crucial in fisheries management. Age of various fish and molluscan species has routinely been determined by counting annual growth bands deposited within the hard structures. In crustaceans such structures were previously believed to be lost and replaced due to molting. However, a technique was recently developed to use growth bands deposited in hard structure retained through molting as an age indicator. In the present study, the applicability of the novel technique is investigated for four crustacean species collected from Northern Atlantic for the first time: European lobster, Homarus gammarus (Linnaeus, 1758); Norway lobster, Nephrops norvegicus (Linnaeus, 1758); Atlantic rock crab, Cancer irroratus Say, 1817; and northern shrimp, Pandalus borealis (Kr0yer, 1838). The gastric mill ossicles in the first three species were processed to show the growth bands while the eyestalk was used in the shrimp species. Four growth bands were visible in European lobster hatched in a Norwegian hatchery and maintained alive for four years before prior processing. Band counts in the other three species were identical to size-at-age interpretation determined from length-frequency analysis. Validation of the periodicity of annual deposition of growth bands is essential before applying the technique on a wider scale. [ABSTRACT FROM AUTHOR]

It has recently been confirmed that some species of decapod crustacean retain their gastric mill and calcified region of the eyestalks throughout their moults. It had previously been assumed that crustacea lost all growth structures that could potentially record age information, such as the bones and otoliths in fish, through moulting. In this study, a novel preparation method was used for observing growth increments within these calcified structures of Nephrops norvegicus and Cancerpagurus (Linnaeus, 1758). This method involved: boiling, drying, resin embedding, sectioning, and polishing the gastric mill and eyestalks. Clear and readable growth increments were observed in longitudinal sections of the mesocardiac ossicle of the gastric mill for N. norvegicus, and longitudinal sections of the zygocardiac ossicle of the gastric mill for C. pagurus. Growth increments were also observed in longitudinal sections of the calcified region of the eyestalk for N. norvegicus. Validation is needed to confirm the periodicity of these growth increments. [ABSTRACT FROM AUTHOR]

Landings of Nephrops norvegicus from North Galicia (Northwest Spain) have decreased by 80% from 1975 to 2001. Variability in the landings per unit effort (LPUE) of this stock was investigated by using time series approach. The LPUE time series (1975–2001) exhibited a seasonal pattern. The seasonal decomposition of the LPUE showed a declining in the trend-cycle component from 1987 onwards. Univariate and dynamic regression ARMA models were fitted to the LPUE time series. Population (proportion of males, proportion of ovigerous females and recruits) and environmental variables (temperature, salinity, nitrates and chlorophyll at 70 m depth, upwelling and sea surface temperature) were tested at different lags as explanatory variables. The proportion of males 4 years ago was the key factor explaining LPUE fluctuations. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the microbial quality of whole Norway lobster ( Nephrops norvegicus ) and Norway lobster tails to optimize handling conditions. This was done by assessing the total viable count (TVC) and characterizing the dominant microbiota. The cultivable microorganisms were quantified via classical microbiological plating methods. To characterize as many bacterial species present as possible, we performed advanced molecular identification techniques (PCR-DGGE). The initial TVC of fresh Norway lobster meat was high (3.0 log cfu/g) as compared to fish. No significant difference between whole Norway lobster and Norway lobster tails could be found during the storage period. From day 6 of storage, a significant difference between Plate Count Agar (PCA) and Marine Agar (MA) was observed. The microbiota of Norway lobster was dominated by members of the Gram-negative genera such as Psychrobacter spp., Pseudoalteromonas spp., Pseudomonas spp., Luteimonas spp., and Aliivibrio spp. From these bacteria, mainly Psychrobacter spp. and Pseudomonas spp. remained present until the end of the storage period. These are known spoilage organisms in fishery products. Other known spoilage organisms of crustaceans such as Photobacterium spp. could not be identified. [ABSTRACT FROM AUTHOR]

Future ocean acidification (OA) and warming following climate change elicit pervasive stressors to the inhabitants of the sea. Previous experimental exposure to OA for 16 weeks at pH levels predicted for 2100 has shown to result in serious immune suppression of the Norway lobster, Nephrops norvegicus . The lobsters are currently affected by stressors such as periodical hypoxia inducing high levels of bioavailable manganese (Mn). Here, we aimed to investigate possible effects of interactions between OA and these stressors on total hemocyte counts (THCs) and on recovery of inoculated bacteria in the lobsters, measured as a proxy for bacteriostatic response. The effects were judged by following numbers of culturable Vibrio parahaemolyticus in hepatopancreas, 4 and 24 h post inoculation in lobsters kept in replicate tanks with six different treatments: either ambient ( p CO 2 ∼ 500 μatm/pH ∼ 8.1 U) or CO 2 -manipulated seawater (OA; p CO2 ∼ 1550 μatm/pH ∼ 7.6 U) for 8 weeks. During the last 2 weeks, additional stress of either hypoxia (∼23% oxygen saturation) or Mn (∼9 mg L −1 ) was added except in control treatments. Our results showed clear effect on bacteriostatic response in Norway lobsters exposed to these stressors. In lobsters kept in ambient seawater without additional stressors, the number of culturable bacteria in hepatopancreas was reduced by ∼34%. In combined treatment of ambient seawater and hypoxia, the reduction was ∼23%, while in the Mn-exposed animals, there was no reduction at all. This was also the case in all OA treatments where mean numbers of culturable V. parahaemolyticus tended to increase. In lobsters from ambient seawater with or without hypoxia, the THC was not significantly different as was also the case in OA without additional stressors. However, in OA treatments combined with either hypoxia or Mn, THC was reduced by ∼35%. While the reduction of culturable V. parahaemolyticus in lobsters was clearly affected by these stressors, we found no notable effects on growth, survival or hemolytic properties of the bacteria itself. Thus, we conclude that this predicted stress scenario is beneficial for the pathogen in its interaction with the host. As OA proceeds, it may force the health of the ecologically and economically important N. norvegicus to a tipping point if exposed to more short-term stressors such as the periodical events of hypoxia and Mn. This could impact lobster condition and biomass and may as well increase the risk for bacterial transmission to consumers. [ABSTRACT FROM AUTHOR]

Nephrops norvegicus (Linnaeus, 1758) is a decapod crustacean of high economic importance found across the northeast Atlantic. Little is currently known about the variation in stomach morphology with body size. In this study, a novel two-stage endocasting technique was used to determine stomach volume in relation to carapace length. Scanning electron microscope images of the teeth of the gastric mill were analysed to determine the changes in gastric mill size and structure with growth. Correlation analysis revealed strong positive relationships between both carapace length and stomach volume, and the size of the gastric mill. These changes are thought to facilitate an increase in size and range of prey species. [ABSTRACT FROM AUTHOR]