We investigated the patterns of occurrence of FAD-associated fish off the coast of Sardinia, Sicily and Majorca (Western Mediterranean). Two working hypotheses are presented to test whether or not “differences exist in fish assemblages at i) the spatial and ii) the temporal level”. Quantitative and qualitative experimental data were obtained from a total of 521 censuses at 17 fish aggregation devices (FAD) using underwater visual observations carried out in Sardinia and Sicily in May-October 2001 and 2002 and a purse seine data set on 3 FADs obtained from a previous investigation carried out in Majorca. The results from the multivariate analysis rejected both hypotheses. In all locations, patterns of fish assemblages were dominated by Coryphaena hippurus, Naucrates ductor, Seriola dumerili, Balistes carolinensis and Trachurus spp., a pattern evident from examining data at bi-monthly intervals. When the most dominant species highlighted with similarity percentage (SIMPER) analysis were analysed with an analysis of variance (ANOVA), a time effect was clearly apparent and subsequently confirmed for four of these five species (B. carolinensis being the exception); the location factor was also found to be relevant (except for the genus Trachurus). We concluded that differences noted were principally due to the “time shift” in the occurrence of these species in the three locations, leading to the assumption that a relationship did exist between the gradual but significant shift in seasonal temperature and colonization at the study locations. Defining selected community structure indices was also important because no reference points are actually available for the pelagic environment in the Mediterranean Sea.

We investigated spatio-temporal patterns of fish assemblages in four small coastal rivers in South-East Ivory Coast. The samples were collected between July 2003 and March 2005 at 8 sampling sites (2 per river: 1 upstream and 1 downstream). A total of 59 fish species belonging to 39 genera, 23 families and 11 orders were captured. Perciforms (30% of the families and 33% of the species), followed by Siluriforms (22% and 22%), Osteoglossiforms (13% and 17%), Characiforms (9% and 10%) and Pleuronectiforms (9% and 3%) were the most abundant orders. Among the families sampled, Cichlidae (20% of the species), Mormyridae (13%), Clariidae (10%), Cyprinidae (10%) and Characidae (8%) were largely represented. Among the 59 fish species captured, we identified fifteen marine/brackish species and two introduced species. To analyse patterns of fish assemblages, we used a non-linear clustering technique, the self-organizing map (SOM). Using SOM, samples were classified into 4 clusters, mainly related to the spatial location of the sampling sites. Except for the distance from the source of the river, environmental variables (width, depth, current velocity) did not show a clear distribution gradient on the SOM map. This pattern was explained by the abundance of estuarine/marine species (i.e. 25% of the species) characterizing the lower course of the rivers studied. Such a distribution of estuarine/marine species colonizing the lower and middle course of the rivers was explained by the absence of dams and contrasts with the patterns observed in more fragmented rivers of Ivory Coast. Therefore, we suggest that these small streams should be preserved in order to permit estuarine/marine species to migrate between streams and the Aby lagoon, thus allowing their large distribution and their reproduction in favourable habitats. We suggest particular attention be given to the Soumié River basin which represents the only preserved stream ecosystem within the Bia River basin.

The Bay of Bourgneuf, France, is a main site of shellfish production. In the marshes along the bay, oyster intensive rearing and fattening need the mass production of microalgae. Salt groundwaters, available in this region, support a large part of this production for aquaculture. Studies carried out by local authorities have brought to the fore the accumulation of lead (Pb) in several samples of algal pastes derived from cultures using salt groundwater. The aim of this study was to compare growth, nutritional value and metal (Cd, Cu, Pb and Zn) uptake of four microalgae grown in two salt groundwaters or in enriched coastal seawater. Cultures of microalgae used in aquaculture (Haslea ostrearia, Phaeodactylum tricornutum, Skeletonema costatum and Tetraselmis suecica) were realised at the laboratory under controlled experimental conditions. Results indicated that salt groundwaters provided cultures with, at least, an equal biomass and a nutritional value similar to cultures grown in enriched seawater. There was no difference regarding metal accumulation whatever the culture medium, except when S. costatum was grown in one of the salt groundwater in which case its cadmium levels were higher and could be above the French guideline level. These observations questioned on the bioavailability of metals in salt groundwaters. It also underlines the specificity of metal uptake and accumulation by microalgae.

Mass budget of the sea bass (Dicentrarchus labrax) farming losses was examined. Experiments were carried out in April, September and November 2001 in tanks of 8.5 m3 containing sea bass of 1, 31 and 53 g, respectively. Samples were taken at the input and discharge points of the tank at hourly intervals over 24 h. They were later analysed for nutrient concentration, as well as particulate organic carbon and nitrogen, chlorophyll a (Chl a) and total bacterial abundance. Despite the high water supply (exchange rate: 50% h−1), NH4 concentration was significantly higher in discharge water than in input water in all three experiments independent of fish size. The same was found to hold true for PO4 for part of the day (April, November) or for the entire day (September). NO3 and SiO2 ions did not show any differences during April. Particulate organic carbon (POC) and nitrogen (PON) were higher in the discharge water in all seasons. Chl a concentration was higher in the discharge water during the entire day in September whereas bacteria presented higher counts in the output water only during part of the day in April. It was found that 5−7% of the nitrogen supplied is released into the water column as fine particulate material in the form of PON and 21−29% as NH4. A small proportion (13−16%) of supplied phosphorus (P) was released as PO4. The results provided in the present paper are useful in assessing environmental changes in water quality in the vicinity of fish farms in the Mediterranean.

The depuration kinetics of the domoic acid from three body parts (i) digestive gland, (ii) adductor muscle+gonad+kidney+foot and (iii) gills+mantle of the scallop Pecten maximus was studied over 154 days. The scallops, which had accumulated the toxins during a Pseudo-nitzschia australis outbreak, were obtained from a natural bed and hung from a mussel raft in two locations (front and centre) and at three depths (2, 6 and 10 m). The time course of the depuration of domoic acid (DA), as well as the environmental variables, were monitored throughout the experiment. The whole body depurated the toxin very slowly (ca 0.007 day−1) decreasing its concentration from ca. 3200 µg DA g−1. Its kinetics was driven mostly by the digestive gland, which accounted for ca. 95% of the total toxin burden from the start of the experiment. Suspending the scallops from a raft increased the depuration rate of the whole body and digestive gland (ca. 30%) and of the edible tissues (15%). Increases of the depuration rate of domoic acid seem to be related to the pair of covariating variables temperature-salinity. Food amount does not seem to have a significant effect.

We present a simulation bioeconomic model based on an age-structured population biological sub-model and an economic sub-model with vessel-specific dynamics, applied to two red shrimp (Aristeus antennatus) stocks in the NW Mediterranean. The model is dynamic, the economic sub-model is disaggregated at the level of vessel and the two sub-models are linked by means of a fishing mortality vector. We analyzed the projection of selected indicators (catches, overall profits, fishing mortality and spawning stock biomass) for the target species of the deep-water trawl fishery in the NW Mediterranean, red shrimp. We built three alternative management scenarios based on input control and we examined the performance of these management strategies against the current management policies. The three alternative management strategies were: i) increase the cost of effort by eliminating the fuel tax exemption currently in place, ii) limit the nominal effort level (days at sea) to current levels, in order to offset the increasing trend observed in the last decade, and iii) change the selectivity patterns of the trawl by increasing mesh size. Our results show that for the two stocks analyzed, any of the three management measures (input controls) would be beneficial both to the stock and the fleets (over the medium and long terms) when compared with the projections over time of the statusquo. Improving the selectivity of the fishing gear is more beneficial than limiting nominal effort or increasing the cost of effort. Comparing the performance of the management strategies on two stocks, one heavily fished and the other moderately so, we show that none of these management measures is able to substantially redress the situation of a heavily fished stock, implying that for the full recovery of heavily fished red shrimp stocks, we need to contemplate even stricter measures of management.

When assessing oyster-reef habitat in estuaries it is important to understand the influence of salinity on the spatial and temporal variability of associated organisms. How comparable is community structure among stations located at different points along the salinity gradients of estuaries or among tidal tributaries that experience different levels of freshwater inflow? Do assemblages vary seasonally in response to changing salinity and freshwater inflow? To address these questions, multivariate techniques were employed to analyze decapod crustacean and fish abundance data. Organisms were collected at three reefs along the salinity gradient of three estuaries: the Caloosahatchee River and estuary, Estero River and Bay, and Faka Union Canal and Bay. Additional collections were made from reefs located near the mouths of Estero Bay's five tidal tributaries. Samples were dominated by the decapods Eurypanopeus depressus and Petrolisthes armatus. Commonly occurring species included the decapods Panopeus obesus, Alpheus heterochaelis and Rhithropanopeus harrisii and the fishes Gobiosoma robustum, Lophogobius cyprinoides and Gobiesox strumosus. Analysis of similarities suggested differences among stations located along the salinity gradients of all three estuaries. Community structure also varied among stations located near the mouths of the tidal tributaries of Estero Bay. Multidimensional scaling identified community structure present at upper stations as distinct from that downstream and at high-flow tributaries as distinct from that near low-flow tributaries. Upper stations and stations near high-flow tributaries were typified by E. depressus and gobiid fishes. Downstream stations and stations near low-flow tributaries were typified by E. depressus and P. armatus. Percent dissimilarity was greatest when upper and lower stations were compared along the salinity gradient or when low salinity and high-salinity sites were compared among tributaries. Within-station sample variability tended to be higher upstream or in association with high-flow tributaries.

A simple system was used to simulate the effect of alternating toxic (paralytic shellfish poisoning toxins) and non-toxic microalgal diets on oyster feeding behaviors and rates of toxin accumulation. These experimental conditions were meant to reflect, to some extent, the incoming and outgoing fluxes of toxic algae observed at the mouth of the Penzé estuary (Northern Brittany, France). Physiological and toxicological parameters were estimated based on fluorescence measurements recorded continuously at the outlet of each experimental tank, which contained a single oyster. Q tox, this variable describes toxin uptake in oysters, it was used (instead of the toxin ingestion rate): i) in simple graphical analyses, ii) as well as in one- and two-compartment models. Results show that toxin uptake varies widely from one individual to another and is not proportional to the concentration of toxic algae in sea water. A one-compartment model with individual fluorescence recordings as “input” data gave questionable results, however, a two-compartment model was found to effectively describe contamination kinetics in oysters. Limitations of this model as well as possible improvements are discussed.

Yellowfin tuna (Thunnus albacares) are known to preferentially occupy the surface mixed layer above the thermocline and it has been suggested that they are physiologically restricted to water temperatures no more than 8 °C colder than surface waters. However, we here report for dive data acquired from a large yellowfin tuna which demonstrate for the first time that this species is indeed capable of making prolonged dives into deep cold waters. A yellowfin tuna (134 cm fork length) caught near an anchored fish aggregating device (FAD) in the Seychelles (Western Indian Ocean) was equipped with an internally implanted archival tag and released. The fish was recaptured 98 days later. As predicted for this species, this fish spent 85% of its time shallower than 75 m (maximum thermocline depth experienced by the fish) but, over the course of the track, it performed three deep dives to 578 m, 982 m and 1160 m. Minimum ambient water temperatures recorded at these depths were 8.6 °C, 7.4 °C and 5.8 °C respectively and varied by up to 23.3 °C from surface temperatures. The fish spent 8.3% of its time in waters more than 8 °C colder than the surface layer and daily experienced a wide range of sea temperatures (mode at 15-16 °C) and of temperatures of the gut cavity (mode at 6 °C). The reason for these dives can not be known. These depths and temperatures significantly exceed those reported in the literature so far and clearly demonstrate that this species has the physiological and behavioral ability to penetrate deep cold sections of the ocean.

The impact of toxic outbreaks of Gymnodinium catenatum, producer of paralytic shellfish poisoning toxins (PSP toxins) and Pseudonitzschia spp., producer of amnesic shellfish poisoning toxins (ASP toxins), was studied throughout the culture cycle of the king scallop Pecten maximus (length from 40 to 100 mm). Toxin concentration, in plankton and in the digestive gland of the scallops, other variables that describe the state of the cultured scallops (mortality, growth, length/weight ratio, gonadosomatic index) and the main environmental conditions (temperature and in vivo fluorescence) were determined from December 2001 to April 2003. Temperature ranged from 14 °C during the winter to 22 °C at the end of July. In vivo fluorescence ranged from not detectable to 25 relative units, with a maximum also recorded at the end of July. ASP toxin levels, in both plankton and organisms, were high during the first half of the sampling period (maximum 450 ng domoic acid L−1, in plankton, and 175 µg·g−1 of scallop digestive gland) when the scallops were juvenile. PSP toxins attained larger concentrations in the second half of the sampling period (maximum of 1.8 nmol L−1 in plankton and 550 nmol g−1 of digestive gland, of gonyautoxins after hydrolysis). Several mortality events took place during the period studied, but none of them coincided neither with an ASP or PSP outbreak nor with long exposure of the scallops to these toxins. One of the recorded mortalities occurred simultaneously with a high concentration of PSP in the scallops, but also with an important spawning. Additionally, it was not coincidental with the bloom of toxic plankton, thus, post-spawning stress seemed to be the main responsible for the mortality. No appreciable effect of ASP or PSP toxinson growth or reproductive state of the cultured scallops was found. Therefore, neither ASP nor PSP toxins appeared to represent a direct threat to the culture of Pecten maximus in that case.

A preliminary economic evaluation of the feasibility of establishing a fishery to process red crab meal (Pleuroncodes planipes) was conducted. Risk assessment indicated that a fishery of nine boats could operate with an average 1.53 benefit-cost ratio (B C−1) and annual net revenues (NR) of US$427 840, and that there is certainty of obtaining economic profit in every season, with a B C−1 > 1 and NR > 0. Total catch and average catch per trip could be reduced from a total baseline catch of 10 328 tons (1735 t meal) to 6061 (1844 t meal), and from a baseline catch per trip of 11.4 t (4.78 t meal) to 6.73 tons (4.85 t meal) without economic losses. There was no possibility for profit when total catch and average catch per trip were, respectively, lower than 5365 t (1648 t meal) and 5.96 t (4.71 t meal). For a single-fishing trip operation, average B C−1 was 1.5 and NR was US$480. We determined that there was a confidence level of 84% to generate profits. To guarantee profits, a catch of 13.5 t per trip (1.35 t meal) should be obtained. Single trips catching less than 3.3 t (0.94 t meal) cannot make a profit. Sensitivity analysis indicated that plant processing efficiency for converting fresh red crab to meal, catch per trip, and sales price of red crab meal were most important in determining B C−1 and NR values. Plant efficiency constitutes the main element that needs to be optimized, particularly management practices to preserve fresh catch quality. A low sensitivity to costs for processing suggests the possibility of negotiating a higher price and the opportunity for processing plants to venture into processing of red crab meal.

The European, native or flat oyster, Ostrea edulis, has been the subject of human-mediated translocation and aquaculture in Europe for centuries and may have diluted or masked natural population genetic structure. Samples of O. edulis from 10 sites in Scotland and The Netherlands, Brittany and Norway were collected and genotyped at up to six microsatellite loci. Numbers of alleles and heterozygosity per locus were high in all populations and were consistent with previous microsatellite studies. There is no evidence that extensive traditional oyster aquaculture has led to loss of allelelic diversity. Deficiencies of heterozygotes against Hardy-Weinberg predictions were common and were probably mainly due to the presence of null alleles. Overall, population differentiation (F st = 0.05) was estimated to be higher than previous studies and could be resolved into four main genetic groups (1) Norway, (2) The Netherlands and Brittany, (3) Scotland apart from (4) Skye. The genetic distinctness of Norway oysters agrees with previous findings. The distinctiveness of the Skye population could be partly due to an artefact of small sample sizes and partly due to the founder effect of importation of Brittany oysters in the 1950s. Further studies are required to ascertain whether the Skye population may be deserving of special conservation status. The results suggest that human aquaculture activities over recent centuries have probably diluted any original local genetic differentiation within Scotland, but that potentially important genetic differentiation still exists at the wider scale across Europe

Killer whale (Orcinus orca) encounters from commercial pelagic trawlers as well as other types of vessels have been documented in several regions of the northeast Atlantic; however, very little published information is available regarding such encounters in mackerel (Scomber scombrus) and herring (Clupea harengus) fisheries, in the waters between northern Scotland and Norway. Mackerel and herring are the two main fish species targeted by the Scottish pelagic fleet, primarily during October to March and June to September, respectively. Encounters with killer whales were recorded during January and February 2006 by observers on a pelagic trawler fishing for mackerel in this area. These recent data, along with historical records collected since 2000, demonstrate the existence of frequent encounters between commercial pelagic trawlers and killer whales. We describe the foraging behaviour displayed by the whales during fishing operations. Killer whales approached the vessels during retrieval of the net, and remained there until this was completed. They were sometimes sighted during steaming and towing, although there was no observed contact with the boat or net at these times. There is no evidence that the presence of killer whales reduced the amount of fish caught by the trawlers or that killer whales ever become entangled in the nets. We suggest that, during the mackerel fishing season, the whales may obtain a significant proportion of their daily energy requirements from this source.

Restoration of shellfish populations is becoming an increasingly common practice worldwide, as natural fisheries succumb to pressures of overharvesting, habitat loss or degradation, and challenges from invasive competitors and pathogens. Primary genetic concerns relevant to shellfish restoration projects are reviewed, using the cupped oysters Crassostrea gigas and Crassostrea virginica as case studies. Molecular genetic tools can be used to delineate the geographic distribution of germ plasm diversity at the species and intraspecific levels, enabling more informed selection of genetic material for hatchery breeding and production. Maintenance of genetic variability and prevention of excessive inbreeding in hatchery stocks may be facilitated by the use of genetic markers for regular pedigree monitoring. The effect of hatchery supplementation on the effective population size of a recipient wild population (Ryman-Laikre effect) is reviewed in light of the population biology of bivalve molluscs, and appears to be minimal. Deployment of selected enhancement stocks may be a valuable tool for improvement of degraded wild populations, reversing the negative effects of generations of selective harvesting. Molecular genetic tools can be used effectively to monitor restoration programs, when the discriminatory power of the marker(s) is high and high-throughput scoring methods currently available are used.

Martinique is a French overseas department whose economy relies heavily on agriculture. Organochlorine pesticides, mainly chlordecone, were used for banana cultivation to eradicate banana weevil over a period of 40 years. Chlordecone is chemically stable,and has a strong affinity for fatty tissues. It is therefore able to bioaccumulate in animals and thereby represent a threat to ecosystems and man. Soils from banana plantations in Martinique are heavily contaminated with chlordecone. Possible transfer of these molecules from agricultural watersheds to the aquatic environment and the organisms that live in it is feared. The hypothesis that ecosystems of Martinique might be highly contaminated with this organochlorine pesticide was investigated. Chlordecone levels were measured in various freshwater and marine species. Data show a heavy contamination of many carnivorous and detritivorous species (fish and prawns). Concentrations measured in wild or farmed tilapia are among the highest ever reported in the literature. Some coastal species (fish and lobster) were also found to be contaminated, although to a lesser extent. Given the biogeochemical behavior of chlordecone, the most likely route of contamination is food. Detected concentrations in marine organisms are below the tolerated limits established by authorities, however, the impact of other sources of exposure, namely, contaminated water and root vegetables, remains to be investigated.

This study describes the in vitro antiviral activity of two species of oyster hemolymph (Crassostrea rhizophorae and C. gigas) collected on Southern Brazilian coastline. Either the acellular and cellular fractions were tested against herpes simplex type-1 (HSV-1), human adenovirus respiratory strain (AdV-5) and simian rotavirus (RV-SA11) by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The evaluation of viral inhibition was performed using four different strategies: simultaneous, pre-infection and post-infection treatments and virucidal assays. The cellular fraction from Crassostrea rhizophorae showed the most prominent inhibition of HSV-1 and AdV-5 replication, particularly in post-infection treatment assay. No inhibition of rotavirus replication was observed. Both oyster hemolymph fractions showed virucidal activity against all tested virus in non-cytotoxic concentrations.

Throughout much of the UK and in Europe generally the native oyster is in a severely depleted state in the wild. In order to address and potentially to reverse this situation Ostrea edulis was designated as a named species in the UK Biodiversity Action Plan as part of a national commitment to the International Convention on Biodiversity. Amongst other initiatives, some of which are summarised in this paper, a feasibility study was carried out to evaluate all the factors, including an economic assessment, relevant to a programme of stock restoration in the UK. The study showed that there is a considerable body of data on the biology, ecology and distribution of O. edulis to inform restoration projects. Appropriate legislation is in place to allow for restoration. Non-marketable costs and benefits were estimated. They provide an idea of the high value that may be placed on biodiversity aspects. Nevertheless, this study also shows that stock restoration can be commercially viable if fishery prices and yields are sufficiently high. Restoration efforts and associated studies elsewhere have shown the potential for success of native oyster stock regeneration, especially in disease-free areas. For these, there is a very strong element of re-creating and conserving an ecological resource. The relaying of cultch is seen as an essential component of a successful oyster restoration programme and the use of sanctuaries is generally considered beneficial. The loss of the standing stock is a limiting factor and re-stocking is an effective strategy. There is a basic genetic similarity of wild European O. edulis populations such that the source of stocks is not critical. There are some problems with hatchery rearing from these, but using breeding ponds or importing part-grown oysters are viable alternatives.

Two sites in North Wales, UK, were compared for growth, survival, immunocompetence and gonad development of Crassostrea gigas. Juvenile C. gigas spat were purchased as a cohort and placed in bags on trestles at the Menai Strait (MS, two heights on the shore) and the Inland Sea (IS) in the summer of 2003. Performance was examined as a function of several environmental parameters; temperature, coloured dissolved organic material absorption coefficient (cDOM), organic and inorganic nutrient levels, chlorophyll a and phytoplankton community composition.Both sites produced variations in growth, as assessed by dry weight indices and condition index, which were found to be lower at IS, where the animals were permanently immersed, than at MS, where they were emersed for at least 1 h/tide (at the low shore height) and 4 h/tide (at the high shore height) during spring tides. Condition index was also significantly higher at MS high shore than at MS low shore. Mortality was low at all sites, though an increase at IS at the end of the trial led to a significantly greater final percentage mortality of 15.6%. Gonad development was limited, particularly at IS where most animals remained undifferentiated. Gonad development was significantly higher at MS high shore than at MS low shore. cDOM, organic and inorganic nutrients were similar at the two areas. At IS the temperature and chlorophyll a levels were higher than MS. The phytoplankton communities were significantly different, with a bloom of Prorocentrum micans dominating at the Inland Sea for much of the experimental period. Differences in the hydrodynamics, as well as Phytoplankton community appeared to be the only parameters that might cause a lower growth rate in the Inland Sea. The possibilities of P. micans having a sub-lethal effect on C. gigas are discussed.

This paper deals with the economic impact of the invasion of a scallop fishery by an exotic shellfish that was accidentally imported some decades ago. The invasive alien species, a slipper-limpet, Crepidula fornicata, is a space competitor for local scallops, and its spread threatens the sustainability of the ongoing scallop restocking program. Facing this invasion, the local fisheries committee has initiated a containment project intending to make the restocking program consistent with the exotic species presence in the fishery. The issue is complicated by the occurrence of occasional toxic micro-algae blooms affecting the scallop fishery. The paper presents a model dealing with the economic impact of the invasive process, and a methodology for cost-benefit analysis of invasion management. According to numerical simulation, the invasion is a serious threat to the economic viability of the restocking program, and invasion management would help maintaining the long term sustainability of the fishery. Sensitivity tests highlight the importance of long term equilibrium scallop catches on the program result, depending on scallop farming technical performance and ecosystem disturbance.