The Venice lagoon is the main Manila clam (Venerupis philippinarum) production site in Europe. Following the unsustainable exploitation of this site (free-access fishery) local authorities have been striving to regulate fishing activities and most clams are produced using mollusc culture techniques based on wild spat harvesting and on its seeding in appropriate, designated culture areas. Therefore, the quality and abundance of wild clam stocks are critical factors that could limit the full development of this activity. The present study aims at assessing Manila clam stocks (spat, adults per square meter) using ordinary kriging, in an area of the Venice lagoon located near the Porto Marghera industrial zone. Previous studies have identified this area as one of the most important natural clam settlement sites in the Venice lagoon. The study area was approximately 1085 ha; 46 sampling stations were examined. Stock assessment (animals were grouped by size and age group), biomass and correlation with sediment texture were evaluated. The results obtained and comparisons with studies from the literature enabled an estimation of clam recruitment potential and an analysis of the conservation status of clam stocks. Thereafter, in view of a full reclamation and an ecological restoration of the study area, different measures are proposed for the sustainable use of this area that include the establishment of a biological protection area and a shared and rational management of the nursery area; these measures could potentially increase the sustainability of clam culture in the Venice lagoon.

Using experimental data and a model to predict size selection based on morphological data, we investigated size selection of redfish (Sebastes spp.) in the grid-based selection systems used in Northeast Atlantic trawls. We found that not all redfish make physical contact with the spacing between the bars in the sorting grids while they pass in the direction of the codend, and therefore the escapement of some undersized redfish depends on size selection in the codend. We estimate that most of the escapement in the combined selection system (consisting of a 55-mm grid and a diamond mesh codend) happens through the grid. We demonstrated that for one of the two grid systems investigated the increase in size selection obtained experimentally by increasing grid-bar spacing is well in line with what could be expected based on the morphology of redfish. However, the size selection observed experimentally was significantly lower than the size-selective potential of the grids estimated based on the morphology of redfish. By computer simulations, we show that a possible explanation for this difference could be that not all redfish that attempt to escape through the grid make their attempt with an optimal angle of attack.

Cupped oysters (Ostreidae, genus Crassostrea) occupy nearshore marine and estuarine habitats worldwide, providing many ecosystem goods and services as well as being a commercially important group of bivalves. In this study, the species identification of an “adulterant” oyster with small body size, which is often misidentified as a “young individual” of other sympatric species, including C. sikamea and C. hongkongensis, was determined for the first time, based on molecular markers (partial mitochondrial cox1 and rrnL genes), phylogenetic analysis, and morphometric approaches. This novel species, C. zhanjiangensis, commonly known as the “cat ear oyster” in Guandu (a famous estuarine oyster farming region of Zhanjiang, Guangdong Province, China), appears to potentially influence the efficiency of C. hongkongensis spat collection due to niche competition on spat collection devices. Phylogenetic analyses confirm its status as the most basal taxon of the Indo-Pacific Crassostrea. A comparative study of the shell characteristics of C. zhanjiangensis, and other Crassostrea species revealed several distinctive morphological traits, including a generally smaller body size, a deeply cupped left valve, and a right valve that is convex in adults but flat in young individuals. Other distinctive features of the new species include life cycle traits that are unique compared with the sympatric C. hongkongensis and C. sikamea species, such as a higher growth rate in the fast growth phase after settlement, followed by a significantly slower growth rate and mass mortality during subsequent life stages. This study provides the basic information necessary for further ecological and population genetic studies on this new species.

We report the isolation, development and multiplex optimisation of 12 new microsatellite loci for the great scallop, Pecten maximus. Diversity was moderate to high, with number of alleles ranging from 4 to 20 and observed heterozygosity between 0.28 and 0.88. Progeny produced in a commercial hatchery was used to test locus power for parentage assignment. The percentage of offspring that was unambiguously assigned to a unique pair of parents was 97% (software package CERVUS-COLONY). Parentage assignment revealed that 22% of the studied progeny resulted from unplanned crosses. Effective population size of the study progeny was also estimated. Our study illustrates the power of microsatellites for the genetic monitoring of hatchery-produced great scallops.

Conservation of threatened large sharks and management of shark-human interactions requires an understanding of shark occurrence and movement patterns. Here, we present the first catch, movement and behaviour data of adult bull sharks, Carcharhinus leucas, in New Caledonia. Amongst six adult C. leucas tagged with passive acoustic tags, four females were caught in coastal waters while males were only found at an isolated oceanic barrier coral reef over 100 km from the nearest river mouth. Two females were monitored in the southern New Caledonia lagoon for 707 and 208 days respectively and displayed classical transient behaviour and sporadic short-term residency around a coastal reef bay, with movements in and out a river detected prior to spring. Adult C. leucas in New Caledonia may develop a sex-based spatial segregation with an atypical presence of adult males in oceanic environments, probably influenced by the unique estuarine-marine continuum of the New Caledonian great lagoon.

Sperm characteristics of scallops have not been well described in the scientific literature. The effects of sperm release technique (thermal shock versus serotonin injection), of sperm collection technique (testis sampling versus serotonin injection), of sperm sampling location along the genital tract, of in vitro sperm maturation, and of time post activation on scallop sperm characteristics were assessed in the present work. Whatever sperm release technique used, no significant differences were observed regarding the percentage of motile spermatozoa and the velocity of the average path (VAP). Compared to testicular sperm, a higher percentage of motile spermatozoa, VAP and intracellular adenosine triphosphate (ATP) content were observed for sperm shed after serotonin injection. From the distal part of testes up to the gonopore, an increase of the percentage of motile spermatozoa and VAP was assessed, suggesting a sperm ‘maturation process’ along the genital ducts. A higher increase in the percentage of motile sperm was recorded during a 5 min incubation of testicular sperm in seawater containing 2 mM serotonin and seawater containing 10 mM caffein compared to seawater (control). In addition, a higher VAP was assessed, incubating testicular sperm in caffein, compared to control or serotonin. Then, the percentage of motile spermatozoa, VAP and intracellular ATP content exhibited a progressive reduction during the 10 h swimming period. Mean values of the percentage of motile spermatozoa, VAP, sperm track linearity (LIN) and intracellular ATP content recorded at the beginning of the movement period for sperm samples collected after intragonadal serotonin injection, were 82 ± 7%, 162 ± 15μm s-1, 0.33 ± 0.12 and 212 ± 133 nmol  × 10-9 spermatozoa (n = 9 males), respectively. The present study confirms the existence of a sperm “maturation process” along scallop genital ducts. In addition, the cessation of scallop sperm movement can be explained by the exhaustion of ATP content at the end of the movement phase.

Populations of the marine molluscan bivalve Dosinia exoleta in Galicia (northwest Spain) present lead (Pb) concentrations above the limit for human consumption. Accordingly, its collection for human consumption was forbidden since 2008. The high bioaccumulation of Pb in this species is surprising given that Pb concentrations are not very high in its environment and that other bivalve infaunal species inhabiting the same areas do not show such high Pb contents. This study reports the discovery and description of extracellular granules present in the kidney tubule lumina of this species. Large granules (20−200 μm) mainly composed of calcium phosphate represent between 50% and 75% of the dry weight of the kidneys. Metal analysis revealed that from 78 to 98% of the Pb body burden was present in the kidney, and from 87% to 92% of this Pb within the kidney was contained in metal rich granules. Most of the zinc in these bivalves was also found to be associated with these kidney granules, while other metals, such as copper and cadmium, were associated with other kidney fractions. This study confirms that the high Pb concentrations observed in D. exoleta, and the relationship of Pb concentration with individual size, are due to the inclusion of Pb in kidney granules that accumulate in the kidney lumen over the course of the bivalve’s life.

Replacing aquaculture feeds based on fisheries-derived resources with plant-based diets could be a relevant strategy to improve the sustainability of aquaculture. Recent studies on sea bass have shown that the total and early replacement of marine products by plant products would have a moderate effect on fish growth and body lipid content. Whether a plant-based diet impacts behavioural and physiological traits possibly linked to fish welfare, is not known, however. Here, we studied the effect of a totally plant-based diet introduced at an early stage of sea bass development on self-feeding behaviour, learning ability in a T-maze and stress biomarkers. We first compared learning processes in self-feeding conditions, between naive fish fed a plant-based diet (PBF) and fish fed a classic marine diet (MF). Then, we tested fish individually in a T-maze to compare the two feed groups for swimming activity, exploration and the ability to learn to discriminate between two two-dimensional objects associated with a reward. Blood physiological variables, including stress indicators (cortisol and glucose concentrations), were also determined. We did not find any indications of differences in self-feeding behaviour between PBF and MF in the first 30 days. A second experiment showed similar swimming activities in both fish categories. The “no-choice” percentage was high in both fish categories (~60%), but all the fish moved preferentially toward the reward. Their first turns indicated an ability to discriminate between two two-dimensional objects to complete a simple task. However, the high percentage of “no-choice” responses in both fish categories could have rendered the results non significant. The T-maze test procedure induced the production of high concentrations of cortisol, indicating acute stress in fish of both groups during testing. Plasma cortisol concentration was higher in MF than PBF, suggesting that the plant-based diet may affect the short-term release of cortisol. This study provides the first insight into the impact of a plant-based diet on sea bass behavioural traits, and confirms the effect of this diet on cortisol release in response to stress. Overall, in this first experiment, we did not find any major impact of a plant-based diet on sea bass behavioural traits, which is an interesting point for the development potential of such a sustainable aquaculture strategy.

The toxic dinoflagellate Alexandrium catenella recurrently blooms on the coasts of France and produces Paralytic Shellfish Toxins (PSTs) that accumulate in bivalves. These toxins can affect various physiological functions including reproduction. The present study aims to validate measurements of sperm viability, DNA content and mitochondrial membrane potential in Pacific oyster Crassostrea gigas using flow cytometry coupled with fluorescent markers, and to use these measurements to assess the cellular parameters of sperm from Pacific oysters exposed to A. catenella. These parameters may influence fertilization, embryogenesis and larval development in free-spawning shellfish. Sperm viability and DNA content estimation were assessed using SYBR-14, which only penetrates cells with intact membranes. Cell mortality was measured with propidium iodide (PI), which penetrates cells with membrane damage. Mitochondrial membrane potential, used as an estimate of mitochondrial function, was measured using JC-1 dye, which selectively enters into mitochondria and reversibly changes colour from green to orange as the membrane potential increases. To assess the effect of toxic algae on oyster sperm, broodstock (ripe oysters) were fed toxic (A. catenella) or non toxic (Heterocapsa triquetra) dinoflagellates at 250 cell ml-1 for 9 days. After this exposure period, mature oysters were stripped and cellular responses of sperm analysed. Average DNA staining, as measured by SYBR-14, appeared lower and more variable in gametes from A. catenella-exposed oysters than in those from control oysters fed H. triquetra. Additionally, mitochondrial membrane potential of sperm from A. catenella-exposed oysters was significantly higher (1.5 fold) than that of sperm produced by oysters fed H. triquetra. Both the increase of mitochondrial membrane potential and the modification of DNA structure can be expected to impact spermatozoa ability to fertilize oocytes and could thus impact related reproductive processes.

Blue marlin are sexually dimorphic in size-at-age and other biological characteristics. However, few studies have examined the possible impact of sexual dimorphism on the population parameters and the ratios of fishing to total mortality (the exploitation ratios) for this species. We analyzed sex-specific catch-at-length data for blue marlin collected from the Taiwanese tuna longline fishery in the northwest Pacific Ocean, ranging between 100–311 cm in eye to fork length (EFL) for females and 100–236 cm EFL for males, and show that the proportion of females in the catch (the sex ratio) increases with length, with females reaching larger body sizes than males. Minor differences in fishery sex ratios among months were observed. Growth parameters, length structures, and natural mortality rates were estimated to differ between males and females, while fishing mortality rates were found to be similar. Nevertheless, the exploitation ratio for females was higher than that for males. We suggest that growth parameters and natural mortality rates should be sex-specific when assessments for sexually-dimorphic species such as blue marlin are conducted, and that management of blue marlin fisheries could be developed based on size limit regulations for large individuals.

Individual Pinctada margaritifera molluscs were collected from the Takapoto atoll (Tuamotu Archipelago, French Polynesia) and used to produce ten first generation full-sib families in a hatchery system, following artificial breeding protocols. After three years of culture, these progenies were transferred to Rangiroa atoll (Tuamotu Archipelago, French Polynesia) and tested for their potential as graft donors. A large-scale grafting experiment of 1500 grafts was conducted, in which a single professional grafter used ten individual donor oysters from each of the ten families, grafting 15 recipient oysters from each donor. The recipient oysters were all obtained from wild spat collection in Ahe (Tuamotu Archipelago, French Polynesia). After 18 months of culture, 874 pearls were harvested. Highly significant donor family effects were found for nucleus retention, nacre thickness, nacre weight, pearl colour darkness and visually-perceived colour (bodycolor and overtone), pearl shape categories, surface defects and lustre, the last two of which are components of the Tahitian classification grade. No significant difference was recorded between the ten G1 families for the absence or presence of rings. The progenies could be ranked from “best” (i.e., the donor whose grafts produced the greatest number of grade A pearls) to the “worst”. Some progenies had extreme characteristics: family B presented the greatest number of pearls with lustre (98%) and a high proportion of dark gray to black with green overtone pearls (70%). These results have important implications for the selective breeding of donor pearl oysters: it may be possible to reach a point where specific donor lines whose grafts produce pearls with specific quality traits could be identified and maintained as specific breeding lines.

Beaked redfish inhabits North Atlantic waters in the depth range 100–950 m, over the continental shelf, slope and the open ocean. Individuals can live demersal or pelagic, at various stages of their life cycle. The geographical distribution of the species extends to most of the Atlantic waters from Newfoundland and the Labrador basin in the west to the Barents Sea in the east. Monitoring beaked redfish is challenging because of the species wide geographical distribution and large scale migrations; deep distribution, which complicates trawling and hydroacoustic surveys; difficulties with tagging; and persistent difficulties in taxonomic identification. These challenges make it a particularly problematic species to observe with conventional research methods. We review these key challenges and provide recommendations for the coordinated observation of Sebastes mentella in the North Atlantic that would best contribute to the assessment and ecological research on this species.

As marine protected areas (MPAs) are increasingly being utilised as a tool for fishery management, their impact on the food web needs to be fully understood. However, little is known about the effect of MPAs on fish assemblages, especially in the presence of different life history and ecological traits. Modelling the observed changes in fish population structures may provide a mechanistic understanding of fish assemblage dynamics. In addition, modelling allows a quantitative estimate of MPA spill-over. To achieve this purpose, we adapted an existing ecosystem model, OSMOSE (Object-oriented simulator of marine biodiversity exploitation), to the specific case of the presence of fish with multiple life histories. The adapted model can manage 4 main categories of life history identified in an estuary MPA: fish that (1) spend their entire life cycle locally, (2) are present only as juveniles, (3) enter the area as juveniles and stay permanently except during reproduction periods, which occur outside the estuary, and (4) are present occasionally and for a short time for foraging purposes. To take into account these specific life-history traits, the OSMOSE code was modified. This modelling approach was developed in the context of the Bamboung Bolong MPA, located in a mangrove area in the Sine-Saloum Delta, Senegal. This was the ideal case to develop our approach as there has been scientific monitoring of the fish population structure inside the MPA before fishery closure, providing a reference state, and continuous monitoring since the closure. Ecologically similar species were pooled by trophic traits into 15 groups that represented 97% of the total biomass. Lower trophic levels (LTL) were represented by 6 compartments. The biomass of the model species was calibrated to reproduce the reference situation before fishery closure. Model predictions of fish assemblage changes after fishery closure corresponding to the Bamboung MPA creation scenario were compared to field observations; in most cases the model reproduces observed changes in biomass (at least in direction). We suggest the existence of a “sanctuary effect”, that was not taken into account in the model, this could explain the observed increase in biomass of top predators not reproduced by the model. Finally, the annual MPA fish spill-over was estimated at 11 tons (~33% of the fish biomass) from the model output, mainly due to diffusive effects.

In the Chausey archipelago, growth of the burrowing bivalve Venus verrucosa (Mollusca: Veneridae) has been shown to be highly variable between closely located sites (<1 km). To explain this small-scale spatial variability, we tested the trophic hypothesis using both fatty acid markers, and carbon and nitrogen stable isotopes (δ13C and δ15N). Environmental parameters, including substrate, were also analysed to discriminate their effects on potential trophic differences. Results of isotopic fractionation and lipid profiles of water column and digestive gland samples both showed a large contribution of phytoplankton to the diet of V. verrucosa. More surprisingly, the same results suggest that Phaeophyceae and Rhodophyceae macroalgae could contribute to the nutrition of V. verrucosa as dissolved exudates. Whereas site differences were not observed between the food sources of V. verrucosa, we showed that growth performance index was correlated to wave height. Thus, we hypothesized that the high local growth variability could be controlled by the hydrosedimentary dynamics. In addition, although no significant growth differences were found between intertidal and subtidal populations, better condition index and more total lipids were found in the digestive gland of intertidal V. verrucosa, suggesting potential compensatory growth mechanisms.

It is estimated that fish aggregating devices (FADs) are now used for over 40% of world tropical tuna catches, making this technique a major phenomenon for high seas fisheries worldwide, and one that has experienced great expansion over the past three decades. The question of whether the FAD is a good or a bad tool for the exploitation of marine resources depends on many parameters. To respond to this question, it is necessary to distinguish different scales of exploitation (artisanal vs. industrial) and various types of FADs (anchored vs. drifting), but it is also very important to gather more data and conduct further research on this topic to gain a better understanding of the phenomenon and of its impacts. As such, twelve years after the first international conference devoted to FADs, which was held in Martinique (French West Indies), a new multi-scalar global assessment of FAD fisheries development and a review of the progress of research in this field was deemed vital. The latest international conference, “Tuna Fisheries and Fish Aggregating Devices”, was held in Tahiti in November 2011, and it was an event that welcomed nearly 150 conference attendees from 40 different countries, three ocean regions, and the Mediterranean. This is an analysis of the relevant literature gathered by the author in the bibliographic database FADBASE. Then, the major issues already addressed by the scientific community are set out, and gaps and research priorities are highlighted for anchored and drifting FADs management.

Through a review of the scientific literature and a more in-depth qualitative meta-analysis of 16 case studies distributed worldwide, this article aims to study impacts of MPAs on marine living resources, ecosystems and related fisheries and to highlight their criteria of efficiency as management tools for a sustainable exploitation. MPAs are efficient for conservation purposes and resource restoration, especially inside their borders. MPAs can also be part of fisheries management systems, but there is a lack of knowledge about their wider scale impacts on fish stocks, ecosystem and fisheries. Adjacent fisheries can increase their catches near closed areas, but such effects are delayed until after MPA establishment and are often limited over distance. Even though local specificities in ecosystems and fishing resources lead to high variability in MPA effects, four major criteria modulate the efficiency of MPAs for fisheries management: (1) the size of the closed area; (2) the level of protection of essential habitats for exploited resources; (3) MPA integration as part of wider integrated fisheries management plans; and (4) efficient monitoring and regulation systems, including participative decision making, to ensure that restrictive measures are respected.

With slow growth rates, late maturity and a high maximum age of 100 years or more, orange roughy can be classified as a vulnerable deepwater fish species that can only sustain low rates of exploitation. Historical patterns of exploitation associated with this species suggest that it is currently not possible to manage its fisheries in the Northeast Atlantic sustainably, and the total allowable catch for orange roughy has been gradually reduced to zero for European fisheries since 2010. Orange roughy to the west of Ireland and Britain occurs on distinct bathymetric features (seamounts, hills and canyons) as well as on flat ground along the continental slope. Productivity-susceptibility analysis (PSA) was performed to evaluate the biological vulnerability of orange roughy in relation to other deepwater species and the risk that recent and current fisheries pose to its populations in the study area. Time-dependant PSA, based on the spatial overlap between orange roughy distribution and recent and current deepwater fisheries demonstrated a strong reduction in risk over time when fisheries stopped directed targeting practices and continued with mixed deepwater trawl fisheries. Some spatial overlap between the species and current fisheries remains, and while the method can show relative risk reduction, it cannot provide information on whether the risk is low enough to allow the recovery of depleted populations.

The mussel (Mytilus edulis) is successfully grown in aquaculture in Europe. Mussels are usually sold live and wet storage is becoming more common. In this study, oxygen demand and ammonia excretion were assessed at increasing water temperatures and different post-harvest situations. This information was used to calculate minimal flow rates per unit biomass of live mussels sufficient to keep oxygen above 5 mg L-1 or 50% saturation, and avoid accumulation of ammonia in commercial wet storage. In this study, rope-grown mussels were kept out of water for 8 h to simulate harvesting conditions and then re-immersed in holding tanks at 5, 10 and 15 °C. Oxygen and ammonia concentrations were measured immediately after mussels were re-immersed (0 h), after 6 h and then every day for 3 days. After this period, the mussels were again kept out of water for 48 h to simulate long-distance transport and once again re-immersed for the same period as before. In the first 6 h after re-immersion, the oxygen consumption was between 7.5 and 12.2 μmol g-1 h-1 (dry flesh) and after this period it decreased to a standard level of around 4.0 ± 0.9 μmol g-1 h-1 and was independent of temperature. There were no major differences in oxygen consumption between mussels having spent 8 and 48 h out of water at any of the subsequent water temperatures used for re-immersion. In contrast, the ammonia excretion showed greater differences according to temperature and time out of water. Ammonia excretion was lowest at 5 °C (<0.01 μmol g-1 h-1). The implications of these results for the industry and authorities are discussed considering the water flow rate, depuration specifications and energy costs.

This study provides a historical overview of the use of drifting fish aggregating devices (DFADs) in purse seine fisheries since the early 1990s, using global tuna fisheries datasets from the four tuna Regional Fisheries Management Organizations (RFMOs). Tropical tuna purse seine fisheries typically target large yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tunas on free-swimming schools and skipjack (Katsuwonus pelamis) and juveniles of yellowfin and bigeye associated with drifting objects. DFADs have enabled global skipjack catches to markedly increase, and have also introduced major scientific issues for all tuna-RFMOs. In particular, they have strongly modified the fishing strategies of purse seiners that fish on a combination of free-swimming and DFAD-associated schools. Consequently, the cumulated search time traditionally used to quantify nominal fishing effort to assess the status of tuna stocks is inconsistent and cannot be used to derive time series of abundance indices from catch-per-unit of-effort (CPUE). In addition, the lack of information available on the construction, deployment, and use of DFADs has prevented effective monitoring of the fishing pressure over the last two decades exerted by purse seine fleets using this fishing mode. Juveniles of tropical tunas represent a substantial proportion of purse seine catch on DFADs in the three oceans, which has raised particular concern for some bigeye stocks that have been subject to overfishing in the past. Catches of juvenile tunas by DFAD fishing may also result in a decrease in recruitment for fisheries that target adult tunas such as longliners. In addition, some demographic parameters of tunas and other species associated with DFADs may be affected by the resultant habitat modification arising from the widespread deployment of DFADs. Evidence in the literature and provided by the ratio-estimator method suggest that fishing DFAD-associated schools may result in about 100 000 t of bycatch and discards annually. In addition, there is further potential for ghost fishing related mortality of sensitive species such as marine turtles and pelagic sharks. In this context and following a precautionary approach, we finally discuss the increasing need for all tuna-RFMOs to reduce, or at least monitor and control, the use of DFADs to mitigate their adverse effects not only on yellowfin and bigeye stocks but also on open-ocean ecosystems.