Search

8 pages, 6 figures, 7 tables, The landing obligation in the revised European Union Common Fisheries Policy allows for exemptions to obligatory landing of the entire catch for species for which “high survival” of discards can be demonstrated. Nephrops norvegicus is an important target species in many fisheries across Europe in the Mediterranean Sea, NE Atlantic Ocean and North Sea. Historically, Mediterranean fisheries have had a high discard rate of small-sized Nephrops, and it is suspected that this unwanted component of the catch may have a high survival potential that is comparable to those of other EU fisheries, where survival rates of up to 0.56 have been demonstrated. However, to date, no investigations have confirmed a high discard survival rate for Nephrops in the Mediterranean Sea. Furthermore, the environmental, technical and biological characteristics that could affect Nephrops survival have been shown to be substantially different from those in the survival assessments conducted in the NE Atlantic and the North Sea. To address this knowledge gap, this study was conducted to determine the survival of Nephrops discarded from trawls in the Mediterranean Sea. The survival and vitality status of the discarded Nephrops removed from trawl catches were monitored onboard and for 14 days in the laboratory. The results showed seasonality in survival, with the highest survival rate in winter (0.74; CI: 0.7−0.78), lower survival in spring (0.36; CI: 0.31−0.41) and the lowest survival in summer (0.06; CI: 0.04−0.09). Survival was monitored to the asymptote in all cases, and season and vitality status were shown to have statistically significant relationships with survival, This work was funded by the research project MINOUW (H2020-SFS-2014-2) of the European Commission (contract n° 634495), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Accepted manuscript version, licensed CC BY-NC-ND 4.0. To prevent unwanted fish bycatch from entering the trawl, we modified a counter-herding device, FLEXSELECT, developed for a Northeast Atlantic Nephrops (Nephrops norvegicus) trawl fishery. FLEXSELECT, which was designed to direct fish away from the trawl by means of sweeping ropes in the herding area, has been shown to be highly effective on both roundfish and flatfish species. However, by adding sweeping elements we could be increasing the benthic impact of trawling. Therefore, in this study we investigated if the effect of FLEXSELECT can be maintained when raising the ropes off the seabed. A reduction in fish bycatch could still be achieved, but the effect of FLEXSELECTraised with respect to the previous design was significantly different for four of the seven species analysed. While for some species the effect was lower, it substantially increased for cod (Gadus morhua), making it highly relevant for the Nephrops fisheries, as well as for other fisheries in needs of avoiding cod catches. The results offer insights regarding species behavioural responses to FLEXSELECTraised, to be used for future developments of counter-herding devices in commercial fisheries without the addition of seabed impact to the baseline gears.

Bottom-trawl fishing for crustaceans off the Portuguese south and southwest coasts is a very important segment of the Portuguese fishing fleet, where annual rates of discarding have ranged from approximately 38% to as much as 70% of the total catch. Past experiments to address this problem encompassed the testing of different codend mesh sizes and configurations, square mesh windows and rigid grids to enhance species and size-selectivity. While the use of a Nordmore grid has proved quite efficient in separating out blue whiting (Micromesistius poutassou), it also led to some losses of the two main crustacean target species, Norway lobster (Nephrops norvegicus) and rose shrimp (Parapenaeus longirostris). The present study addresses that limitation by using a modified grid with 20 mm bar spacing and two open sections, designed with the purpose of separating fish and crustacean species into upper and lower codends. Good separation was achieved, with about 80% of the blue whiting (in number) directed towards the upper trawl section and caught in the upper codend, while a similar percentage of Norway lobster was caught in the lower codend. The grid bars had 50% retention for Norway lobster at 34.1 mm carapace length. The results herein will enable this gear configuration to be finetuned with regard to codend mesh sizes and bar spacing, so as to optimize both retention of Norway lobster and exclusion of blue whiting. For example, compared to using the minimum 70 mm diamond mesh size, using an 80 nun diamond mesh upper codend would reduce Norway lobster catch weight by just 1.6% but reduce the number of blue whiting caught by 42%. [22-05-01-FDR-00014]

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.fishres.2018.03.020. In the laboratory, we investigated which sizes of Nephrops (Nephrops norvegicus) could pass through the meshes of different size and shape to establish a predictive model for the creels size selectivity. Predictions agreed well with the results from experimental fishing, demonstrating the reliability of this simple method. Nephrops minimum target size is 20 mm carapace length in the Mediterranean creel fishery, with some areas having restrictions on the mesh size, minimum being 36 or 40 mm. The model predicts that Nephrops below 28 and 32 mm carapace length would escape from creels with respectively 36 and 40 mm mesh size, implying a suboptimal exploitation pattern. Our method provides easy and quick identification of optimal mesh size and shape without the exhaustive sea trials with various creel designs. It was predicted that a square mesh of 30 mm would better match the desired exploitation pattern. The method could easily be adopted to other species and different creel fisheries, helping to determine optimal mesh matching a prescribed exploitation pattern.

A promising design to improve selectivity in the Nephrops-directed trawl fishery is the horizontally divided trawl codend. Previous studies have succeeded in separating the majority of fish from Nephrops; however, cod (Gadus morhua), juvenile roundfish and flatfish still enter the lower compartment in relative high proportions. In this study we investigated if and to which extent it is possible to improve the vertical separation of fish from Nephrops by adding active behaviour stimulators. These stimulators are designed to exploit fish avoidance behaviour and lead them into the upper compartment while Nephrops move into the lower compartment. We tested two types of behaviour stimulators: a chain curtain at the entrance of the lower compartment at the point of separation and a set of rising float-lines inserted ahead of the point of separation. The length-dependent vertical separation of five important commercial fish species and Nephrops was analysed in comparison to the horizontally divided trawl codend with no stimulator, towed in parallel to the test trawl. The results showed that fish’s vertical separation can be partially improved by the addition of stimulators, without complicating fishing operations or increasing the proportion of Nephrops that enters the upper compartment. However, the improvement was limited and none of the two active stimulators tested managed to simultaneously improve the separation of cod, juvenile roundfish and flatfish.

Maturity size, reproductive cycle, sex ratio and fecundity of female Nephrops were investigated at SW, S and SE Iceland for the period 1960-2010. Time series of biological parameters and fisheries data displayed significant relationships. In addition, female biological data from 20 areas in the Atlantic and Mediterranean were compared. Fifty percentage maturity estimates had an overall range of 23.9-34.4mm CL with some anomalies in the 2000s. The reproductive cycle in Iceland has been biennial during the whole study period from mid-1960s to 2010 with minor change in phase in the 2000s. Biennial moulting retards female growth more than annual spawning, and the length of incubation and hatch time of year show significant relationships with latitude and sea temperature. Variations in sex ratio were observed and relationships found between female sex ratio and CL, CPUE and stock biomass during 1961-2010, displaying apparent fishery-induced effects on sex ratio. Potential and realized fecundity estimates in Iceland are 35-50% of those reported from more southerly waters. Biennial spawning and low fecundity limit the number of progeny in Icelandic Nephrops and necessitate lower fishing mortality. Ambient temperature in Icelandic waters has risen by 1°C since the late 1990s, generating around 30 days shorter incubation time in the 2000s, but around 3°C rise is necessary for possible annual spawning.

9 pages, 7 figures, 3 tables, In this study, we present and test the functioning of a automated multi-flume actograph that is able to simulate concomitant geophysical cycles (day-night and hydrodynamic cycles) characterizing the benthic environment of continental margins. The burrowing Norway lobster (Nephrops norvegicus, L.) was used to test the functioning of the device. The system is endowed with pumps and a pipe system for periodical current flow generation. Monochromatic blue light cycle (472 nm) was provided by submergible LED's lighting strips. Locomotor activity of 8 individuals was tracked by 4 HD video cameras during a 10 days trial. A customized automated video-imaging protocol in MATLAB calculated displacement of animals (cm/min). The functioning of the system was tested simulating an Atlantic continental shelf scenario (i.e. light intensity of 4 · 10− 3 μE/m2/s and current flow at 10 cm/s). Robust time series outputs of nocturnal phase were reported, with the first laboratory evidence of the influence of current flow on burrow emergence of the species. Water flow increase inhibited lobster movement generating a dual reaction in relation to their burrow emergence phase. The method presented here could be pivotal to study unknown aspects of Norway lobster ecology, This work is supported by RITFIM project (CTM2010-16274; PI: J. Aguzzi) founded by the Ministry of Science and Innovation (MICINN). [...] VS is a Predoctoral Fellow within the Formation Personal Investigador (FPI) scheme (MICINN). JA is a Ramón y Cajal Program (MICINN) Postdoctoral Fellow

The Norway lobster Nephrops norvegicus lives at low-light depths, in muddy substrata of high organic content where water salinities are high and fluctuations in temperature are moderate. In this environment, the lobsters are naturally exposed to a number of potential stressors, many of them as a result of the surficial breakdown of organic material in the sediment. This process (early diagenesis) creates a heterogeneous environment with temporal and spatial fluctuations in a number of compounds such as oxygen, ammonia, metals, and hydrogen sulphide. In addition to this, there are anthropogenically generated stressors, such as human-induced climate change (resulting in elevated temperature and ocean acidification), pollution and fishing. The lobsters are thus exposed to several stressors, which are strongly linked to the habitat in which the animals live. Here, the capacity of Nephrops to deal with these stressors is summarised. Eutrophication-induced hypoxia and subsequent metal remobilisation from the sediment is a well-documented effect found in some wild Nephrops populations. Compared to many other crustacean species, Nephrops is well adapted to tolerate periods of hypoxia, but prolonged or severe hypoxia, beyond their tolerance level, is common in some areas. When the oxygen concentration in the environment decreases, the bioavailability of redox-sensitive metals such as manganese increases. Manganese is an essential metal, which, taken up in excess, has a toxic effect on several internal systems such as chemosensitivity, nerve transmission and immune defence. Since sediment contains high concentrations of metals in comparison to sea water, lobsters may accumulate both essential and non-essential metals. Different metals have different target tissues, though the hepatopancreas, in general, accumulates high concentrations of most metals. The future scenario of increasing anthropogenic influences on Nephrops habitats may have adverse effects on the fitness of the animals.

This review focuses on the Norway lobster (Nephrops norvegicus) as a resource, describing how the fishery has developed from the 1960s to the present day to become one of the most economically important fisheries in Europe. In 2010, the total landings were 66,500 tonnes, of which UK fishers landed a significant part (58.1%). The Nephrops fishery is also important for countries such as Ireland (11.7% of the total) and Sweden (1.9%) where it is of regional importance. Some are also taken in the Mediterranean, where Italian, Spanish and Greek fishers together take approximately 7% of the total landing. More than 95% of Nephrops are taken using single- or multi-rig trawlers targeting Nephrops or in mixed species fisheries. In regions such as Western Scotland and the Swedish West Coast, creel fisheries account for up to a quarter of the total landings. Across the range, a small proportion (

65 pages, 10 figures, 2 tables, The Norway lobster is one of the most important commercial crustaceans in Europe. A detailed knowledge of the behaviour of this species is crucial in order to optimize fishery yields, improve sustainability of fisheries, and identify man-made environmental threats. Due to the cryptic life-style in burrows, the great depth and low-light condition of their habitat, studies of the behaviour of this species in its natural environment are challenging. Here, we first provide an overview of the sensory modalities (vision, chemoreception, and mechanoreception) of Nephrops norvegicus. We focus particularly on the role of the chemical and mechanical senses in eliciting and steering spatial orientation behaviours. We then concentrate on recent research in social behaviour and biological rhythms of Nephrops. A combination of laboratory approaches and newly developed tracking technologies has led to a better understanding of aggressive interactions, reproductive behaviours, activity cycles, and burrow-related behaviours. Gaps in our knowledge are identified and suggestions for future research are provided. © 2013 Elsevier Ltd., Part of discussed findings was obtained within the framework of the RITFIM Project (CTM2010-16274; IP, J. A.). J. A. is a Postdoctoral Fellow of the Ramón y Cajal Program (Ministerio de Ciencia e Innovación, MICINN)

The large reniform eyes of the reptant, tube-dwelling decapod Nephrops norvegicus are described in detail. Optically these reflecting superposition compound eyes are a little unusual in that they are laterally flattened, a feature that may enhance their sensitivity in that region, albeit at the expense of resolution. Electrophysiological and anatomical investigations suggest that the eyes are tuned to appropriate spectral and temporal sensitivities in the long and short term through movement of proximal pigments and possibly rhabdom adaptation. Although exposure to ambient surface light intensities is shown to cause damage to the retinal layer, especially in deeper living animals, there is no evidence yet that demonstrates an impact of eye damage on their survival. It is suggested that experimentation on marine decapods, with sensitive eyes, requires that particular attention is paid to their light environment.

This review summarizes the data on habitat, population ecology and ecosystem roles of Nephrops norvegicus. The species has a broad range in the northeast Atlantic and Mediterranean, although it is possible that small or isolated patches of suitable habitat may not be occupied due to restrictions on larval supply. Nephrops densities are related to the silt–clay content of sediments, with interactions between habitat quality and density indicating competition for resources. An analysis of density–size interactions across fishery functional management units (FUs) suggests that growth is suppressed at high densities due to competition (e.g. in the western Irish Sea), although recruitment dynamics or size-selective mortality may also shape the size structure of populations. Nephrops biomass available across FUs may be similar, reflecting a constant yield due to the inverse relationship between individual size and population density. Gaps in the understanding of Nephrops’ ecology reflect uncertain ageing criteria, reliance on fisheries-dependent data and few if any undisturbed habitats in which to examine fisheries-independent interactions.

This chapter presents and explains the position of Nephrops norvegicus in the classification of lobsters. Covered, in order, are systematic classification of Nephrops, taxonomic history of Nephrops, and analysis of Nephrops in nephropid phylogeny. The genus Nephrops was erected by Leach in 1814 and has a long and interesting taxonomic history. Prior to 1972, Nephrops was known by 14 Recent species. All but one of these, N. norvegicus, were removed to a new genus, Metanephrops, by Jenkins (1972) . Today, N. norvegicus is still the only known living representative of the genus. Similarly, Nephrops is known by only one fossil species, the Miocene Nephrops kvistgaardae, although several other fossil species have been previously referred to this genus. Nephrops, along with the other familiar and commercially important marine clawed lobsters, is referred to Family Nephropidae, one of 17 marine clawed lobster families arrayed in 3 infraorders, 6 families each in the Astacidea and Glypheidea and 5 in the Polychelida. Infraorder Astacidea includes the Superfamily Nephropoidea, as well as the lesser known ‘reef lobsters’ of the Superfamily Enoplometopoidea, and the freshwater crayfish, Superfamily Astacoidea. In phylogenetic analyses, the freshwater crayfish form a sister group to the Nephropoidea. It is interpreted that freshwater crayfish evolved from nephropoid lobsters, but from which lobster group is uncertain. The taxonomic placement of N. norvegicus is stable at all levels, from species on up. Despite that, the phylogenetic relationships of Nephrops to other nephropid genera are unsettled due to conflicting results in morphological and molecular analyses. Currently, new morphological characters and new genes are being analysed in the hope of elucidating nephropid phylogeny.

Nephrops norvegicus represents a very valuable fishery across Europe, and the species possesses a relatively complex life cycle and reproductive biology across spatial and temporal scales. Insights into embryonic and larval biology, and associated abiotic and biotic factors that influence recruitment, are important since this will affect population and species success. Much of the fishery, and indeed scientific sampling, is reliant on trawling, which is likely to cause direct and indirect stresses on adults and developing embryos. We have collated evidence, including that garnered from laboratory studies, to assess the likely effects on reproduction and population. Using know-how from hatchery operations in similar species such as Homarus sp., we also seek to optimise larviculture that could be commercialised to create a hatchery and thus assist stock remediation. This review chapter is therefore divided into three sections: (1) general N. norvegicus reproductive biology, (2) life cycle and larval biology and (3) a comprehensive review of all rearing attempts for this species to date, including a likely way forward for pilot scale and hence commercial restocking operations.

5 pages, 3 figures, The aim of the study was to analyse the size, growth and size at maturity of Nephrops norvegicus in two areas off the Portuguese coast. Samples were collected between September 2006 and January 2007. A total of 2081 individuals ranging between 25 and 88 mm carapace length were collected, measured and sexed. The estimated growth parameters were L∞ = 88.33 mm CL, k = 0.38 years−1 for males and L∞ = 64.45 mm CL, k = 0.38 years−1 for females in the northern area, and L∞ = 94.86 mm CL, k = 0.41 years−1 for males and L∞ = 69.20 mm CL, k = 0.44 years−1 for females in the central area. Size at maturity was 50.7 mm CL in the northern area and 46.9 mm CL in the central area, This work was supported financially by SGMAR of the Spanish MARM as part of the APPE 29/2005 project

The recovery potential of Norway lobsters ( Nephrops norvegicus ) held in on-board seawater tanks after trawl-capture was assessed at two different times of the year (winter and summer). Survival recorded 24 h after trawl-capture was 84.83 ± 0.93% in the winter compared to 75.35 ± 2.92% in the summer. Stress-related parameters in the muscle (arginine phosphate, glycogen and L-lactate) and in the haemolymph (L-lactate) were measured, together with nucleotide breakdown products in the muscle (yielding the “Adenylate Energy Charge” or AEC ratio). All parameters analysed were responsive to the stress of the trawl-capture and subsequently recovered towards resting values, but did so at different rates. The fact that some measures recovered at a faster rate than others should be taken into account when trying to develop an index of metabolic stress for this species. Animals trawled in the winter recovered to AEC values above 0.8 within 4 h of placing them in on-board seawater tanks, whereas animals trawled in the summer took 24 h to reach these values. Furthermore, at the end of the trials animals trawled in the summer presented significantly higher haemolymph L-lactate and lower muscle glycogen reserves than the animals trawled in the winter, suggesting a faster recovery in the winter compared to the summer. Finally, animals in the winter were better able to endure further stresses (an emersion of 1 h while animals were transported to the commercial handling facilities). Therefore, as a code of practice it is advised that trawled N. norvegicus directed to the live trade should be allowed to recover for at least 4–6 h in on-board tanks, and extra care should be taken especially in the summer, if further stresses such as additional emersion are to be applied within the first 24 h after capture.

A comparison was made of the effects on melanosis development in Norway lobsters (Nephrops norvegicus) of treatment by dusting with a commercial sulphite-based product and of spraying with a formulation containing 4-hexylresorcinol (0.1% and 0.05%), in combination with organic acids and chelating agents. The following tests were performed during chilled storage: polyphenol oxidase (PPO) activity, melanosis score, colour parameters, tyrosine and tyramine content, as the main substrate of PPO. Differences among treatments were evaluated by means of statistical analyses (ANOVA, principal components and discriminant analyses). All formulations diminished PPO activity during storage successfully. The melanosis score was higher in sulphite-treated Norway lobsters, and a formulation with 0.05% 4-hexylresorcinol was enough to prevent the appearance of melanosis for 12 days. The tyrosine content decreased during storage, but the tyramine content was insignificant. Formulations with 4-hexylresorcinol improved the appearance of Norway lobsters, in comparison with the commercial sulphite-based product. © 2005 Elsevier Ltd. All rights reserved.

8 páginas, 7 figuras, 2 tablas, The use of slurry ice is gaining increasing importance as an advanced method for the hygienic and efficient chilling and sub-zero storage of aquatic food products. In this work, this technology was applied as a novel technique for the chilling and storage of Norway lobster (Nephrops norvegicus) – a crustacean species of high-commercial value – under refrigeration conditions at 1.5 C. In addition, the effects of a preliminary treatment with 0.5% Na HSO3 on surface browning were evaluated and compared with the results obtained in control batches not subjected to such treatment. The processing of lobster in slurry ice significantly (p < 0.05) slowed down microbial spoilage, as determined by the counts of aerobes, psychrotrophs, proteolytic bacteria, and lactose-fermenting Enterobacteriaceae, and by the formation of volatile amines. Likewise, the autolytic breakdown mechanisms – as determined by the K value – were also significantly (p < 0.05) inhibited in the slurry ice batch. Remarkably, preliminary treatment with 0.5% sodium metabisulphite permitted better maintenance of the parameters involved in sensory quality – especially as regards the aspect of the carapace – as compared with nontreated batches, and allowed a shelf life of 9 days without surpassing the 150 mg/kg legal limit established for this food additive. On contrast, the non-treated batch stored in slurry ice exhibited a shelf life of 5 days. The combination of technological treatments proposed in this work – preliminary antimelanosic treatment and storage in slurry ice – may be successfully applied to other fresh and frozen shellfish species with a view to extending shelf life and to avoiding the legal and toxicological problems derived from current abuse of such antimelanosic agents to prevent shellfish browning., This work was supported by the Dirección Xeral de I + D + I from the Xunta de Galicia (Galicia, Spain) (Project PGIDTI02RMA18E).

9 pages, 7 figures, The Norway lobster Nephrops norvegicus lives in the continental margins of the western Mediterranean Sea at depths between 100 and 600 m. It constitutes an important fisheries resource and presents a seasonal reproductive pattern. Female Norway lobsters were obtained each month from a vessel fishing off Barcelona. One hundred females caught in June 2002 were kept in the laboratory. After spawning, ovarian samples were taken every 30 days with the objective of monitoring the first steps in ovarian maturation. The gonado-somatic index (GSI) remained low over the 6 months during which the females carried their eggs, plus for a further 2–3 months. However, this study suggests that ovarian maturation is a continuous process with two different phases, taking at least 6–8 months during which the female carries its eggs. There is an increase in oocyte numbers; the germinal zone produces oogonia; and the oocytes that develop migrate to the periphery, pushing the post-ovulatory follicles to the wall of the ovary and reinforcing it for subsequent spawning. Besides this increase in the number of oocytes, vitellogenesis begins 2–3 months after the eggs hatch. Oocytes then grow and the ovaries gain weight and change from a cream color to a blackish-green. When the GSI reached 10, spawning occurred and, from then on, the ovary is mainly composed of post-ovulatory follicles., This paper is a product of the Spanish CICYT Project BIFICRUST (REN2001-0729)

9 pages, 4 figures, 1 table, The commercial fishery for Nephrops norvegicus in the Western Mediterranean is mainly centred on fishing grounds on the slope at depths between 200 and 500 m. Seasonal variations in catches of this species were studied using commercial data spanning nearly a decade, as reported by fishermen’s association registers of the Catalan trawlers harboured in Barcelona. Time series of monthly landings data (i.e., total kg of captured individuals) were screened with periodogram analysis revealing a six monthly-based periodicity. Form estimate analysis showed a major peak occurring in spring–summer and a minor peak in autumn. These results were evaluated by considering the effect of seasonal variations in light intensity and photoperiod duration as main environmental factors modulating emergence behaviour in the species. Other factors affecting behaviour, such as moulting and reproduction, were also taken into account, The present work was carried out in the framework of a national research project funded by the Spanish Interministerial Council for Science and Technology (CICYT) (NERIT: MAR98-0935).

The effects of an increase in cod end mesh size from 55 to 60 and 70 mm and a change of mesh configuration from diamond to square mesh on the size selectivity for rose shrimp Parapenaeus longirostris and Norway lobster Nephrops norvegicus captured off the Portuguese south coast were evaluated. The results were analysed taking into account between-haul variation in selectivity, and indicate a significant increase in L-50 for rose shrimp with an increase in mesh size or with the use of a square mesh cod end, while for Norway lobster only mesh configuration was found to affect this parameter. Two other important external variables were identified; the trawling depth and the cod end catch, which influence between-haul variation, by increasing the selection range for rose shrimp and Norway lobster, respectively. The results obtained suggest that an increase in the current minimum mesh size of 55 mm would be advisable for rose shrimp in order to respect the minimum landing size of 24 mm carapace length presently established for this species. Moreover, trawling for rose shrimp should be avoided at depths above 200 m, in order to avoid catches consisting almost exclusively of juveniles. Such an increase in mesh size would have a minor impact in terms of losses of individuals above the minimum landing size for Norway lobster and would contribute to reducing the amount of discards in this fishery. (C) 2002 Elsevier Science B.V. All rights reserved.

The catch composition of two commercial vessels of the trawl fleet operating from Mallorca (Balearic Islands, western Mediterranean) was analysed. A total of 4959 kg resulting from 144 fishing hours was sampled from October 1996 to December 1997. The fishes represented the major proportion with respect to the total catch. The analysis of the fish discards assembled them in three depth related groups: group A (mean depth 300 m); group B (mean depth 489 m); and group C (mean depth 616 m). Species richness, number of individuals and biomass decreased with depth. The diversity and evenness indices also varied with depth, but no significant differences were found. Fishes, with around 70%, dominated the biomass discarded in the three depth groups. Within the landings, fish biomass also represented the major proportion in groups A and B, but in group C the crustaceans biomass dominated. Our results confirm that an important fraction of the catch of the two deep-sea decapod crustacean fisheries is discarded., This paper is a result of the European Project Developing deep-water fisheries: data for their assessment and for understanding their interaction with and impact on a fragile ecosystem (EU FAIR PORJECT CT 95-0655; European commission DG-XIV, Fisheries).

17 pages, 3 figures, 6 tables, Length-based methods were used to study age and growth of Nephrops norvegicus in the Catalan Sea. The width of the class interval was examined and 1 mm was found most appropriate for the carapace length-based analysis. Two direct methods, Bhattacharya's and Cassie's, and one indirect, ELEFAN I, were used for age determination. Cassie's method was found very subjective and inadequate, while Bhattacharya's and ELEFAN I more effective, easy to apply and more objective. The results of Bhattacharya's method showed the best agreement with those derived from captivity studies; seven age groups were well defined for males and four for females. Mature female age groups were difficult to detect by any method, indicating the effect of reproduction on female growth. Growth parameters of the Von Bertalanffy model and of the seasonally oscillating Von Bertalanffy formula, estimated by FISHPARM and ELEFAN I, were quite close to those derived from captivity studies. ELEFAN I seemed to produce the best results and the Von Bertalanffy model was not found to be superior to its seasonal counterpart, a fact that gives reason for futher studies. Pauly's empirical formula for fish, used for the estimation of instantaneous natural mortality of this species gave reasonable values. The similarity between the results of the present work and those derived from captivity studies, gives support to the potential use of length-based analysis for the estimation of N. norvegicus biological parameters; however, many factors should be taken into account in order to achieve representative samples suitable for length-based analysis

Beam trawl catches of Dichelopandalus bonnieri in 75-80m depth off the S.W. Isle of Man show greatest numbers in the afternoon, sunset and sunrise. Evidence suggests that the shrimps swim up off the bottom at night and during the morning, possibly as a mechanism of dispersal and avoidance of bottom-feeding fish. Feeding appears to take place on the bottom, D . bonnieri probably competing for food with, and sometimes being eaten by Nephrops norvegicus which emerges from its burrows to feed at approximately the same time of the day.

Nephrops norvegicus (L.) was sampled from a depth of 90m (± 10m) in repeated trawl hauls over periods of 24hr at approximately monthly intervals for three years. Peak catches occurred two hours before dusk and two hours after dawn, correlated with changing light intensity rather than absolute light levels. Timing of peak catch is discussed in relation to feeding, predation, irradiance and behavioural rhythms.

After an incubation period of 8–10 months, eggs attached to the pleopods of the female parent hatch in April–June during a few minutes 2–3 hours after dusk on 5–20 successive days. Hatching is effected by bursts of vigorous pleopod activity causing the release of a proportion of larvae which have completed their embryonic development. By trapping newly-hatched larvae and simultaneously recording locomotor activity of the parent, the hatching process is studied and manipulated in different artificial LD regimes. Both dawn and dusk determine the time of hatch. A rephased rhythm can be induced which persists in both LL and DD.

6 pages, 3 figures, 2 tables, The study of the rate of oxygen consumption by Nephrops norvegicius (L.) at each moulting stage has been carried out in closed respiration chambers, using an oxygen electrode to measure the oxygen concentration. Although the mean respiration rate seems to be low when compared with other decapod crustaceans of similar weight, the general trends of the variation of the oxygen consumption during the moulting cycle are similar to those described for other species of decapods. It should be noted that, during the process of the ecdysis, there is no oxygen consumption. © 1981