Adult oysters Crassostrea gigas were experimentally fed with Alexandrium catenella and Alexandrium minutum which are responsible for recurrent toxic blooms in French coastal waters. C. gigas produced faeces and pseudofaeces containing intact and viable temporary pellicular cysts of these two Paralytic toxin producing species. When incubated in favourable conditions, these pellicular cysts were able to germinate at high rates (between 74 and 94%) and the resulting vegetative cells divided with growth rates close to the non- ingested cells (control). The toxin profile of the vegetative cells originated from the germinated temporary cysts was analyzed by liquid chromatography/fluorescence detection. Total toxin content of newly germinated cells was lower than that of cultured cells. Besides, cell contents of C2, B1, B2 and dcGTX3 toxins featured some changes. Our results suggest that the increased spreading of toxic dinoflagellates through the transfer of shellfish from contaminated towards pristine coastal areas cannot be ruled out. We also suggest that pellicular cysts and newly germinated cells could represent a potential way for the transfer of paralytic toxins toward the higher trophic levels.

Live preys commonly used in fish larval rearing seem to be imbalanced in terms of amino acids. Manipulation of their amino acid composition is difficult, but the use of microencapsulated diets allows this manipulation. This study analysed the effect of amino acid supplementation, in order to compensate for dietary amino acid imbalances, on growth and survival of gilthead seabream (Sparus aurata) larvae. Larvae were reared until 32 days after hatching, in a closed recirculating water system (19 °C), using only live food (rotifers and Artemia). Thereafter, larvae were fed Artemia or one of the experimental microencapsulated diets: supplemented with indispensable amino acids (IAAsup diet), or supplemented with dispensable amino acids (DAAsup diet). Experiment lasted for 10 days. Dietary supplementation with indispensable amino acids resulted in A/E ratios [(each indispensable amino acid) × (total indispensable amino acids)−1 × 1000] more similar to the ones of larval seabream and in higher IAA:DAA ratios than in the DAAsup diet. Survival was similar in larvae fed the IAAsup diet (75%) or Artemia (87%), but was significantly lower in larvae fed the DAAsup diet (52%). Larvae from all treatments more than doubled their average dry weight during the experimental period. Final dry weight was similar in larvae fed both microcapsules, but these were lighter than larvae fed with Artemia. Relative growth rate (RGR) and total biomass production tended to be higher in larvae fed the IAAsup (RGR = 9% day−1) than the DAAsup diet (RGR = 7.5% day−1) and only in this last treatment these parameters were significantly lower than in larvae fed with Artemia. Therefore, dietary supplementation with indispensable amino acids resulted in a more balanced dietary amino acid profile, which significantly increased survival. Further studies introducing microdiets earlier in the development seem necessary in order to optimise growth.

To study the behavior of dolphinfish (Coryphaena hippurus) around drifting Fish Aggregating Devices (FADs), we tagged individuals with long-lived, coded sonic transmitters and attached automated sonic receivers to drifting FADs in two regions of the Western Indian Ocean. Among the three tagging methods used in this study (surgery, external hooks, underwater bait without capture), the latest resulted in residence times significantly shorter than the other ones, likely due to regurgitation. Dolphinfish tagged with the two other methods usually stayed several days associated to FADs (Kaplan-Meier survival analysis 5.09 days, mean 6.25 days, SD 4.39 days, maximum 15.26 days), drifting with them. There was no significant difference in the residence times of dolphinfish in equatorial and tropical areas. While associated to FADs, dolphinfish spent most of their time close to floating object (<365 m). The total time spent away from FADs was low (median 8%), and likely corresponded to making feeding excursions. Dolphinfish did not form a single school while associated to a given FADs, but formed multiple small schools. FADs are likely to be sites with exchanges of individuals between schools. These results are discussed in regards to the possibility of FADs acting as ecological traps and the validity of meeting-point hypotheses as an explanation for fish aggregations under floating objects.

We tested cross-species amplification of 68 existing microsatellite loci in 6 species of the Sparidae family: Acanthopagrus butcheri, Sparus aurata, Pagrus auratus, Chrysophrys major, Pagellus bogaraveo, Pagellus erythrinus and one species of Bothidae, Paralichthys olivaceus. Of the 68 loci screened, sixteen were found to be polymorphic when tested in 20 individual black sea bream, Acanthopagrus schlegeli. The number of alleles per locus ranged from 2 to 9, and the observed and expected heterozygosity ranged from 0.55 to 0.95, and from 0.58 to 0.87, respectively. Our results show that cross-species amplification of known microsatellite loci in closely related species is a highly promising source of microsatellite markers for A. schlegeli.

In October and November 2003 a bloom of the toxic dinoflagellate Alexandrium catenella was observed in the North-east zone of Thau lagoon (French Mediterranean coast). Sea water samples were collected every hours to evaluate time-related variations of phytoplankton concentrations and to compare the relative ratio of A. catenella versus other phytoplankton species during the outbreak. From these observations, trials using recirculated sea water systems were performed to: i) evaluate the physiological effects on oyster of increasing proportions of A. catenella within a mixed microalgal diet where the non-toxic diatom Thalassiosira weissflogii was present at concentration: 1500 cells ml−1, ii) compare the effect of two temperatures (12 °C and 18 °C) on paralytic toxin accumulation rates in oyster flesh by ion-pairing high performance liquid chromatography (IP-HPLC) detection, iii) analyse toxin biotransformation during the contamination process, iv) evaluate the role of the different types of oyster tissue on the bioaccumulation mechanism.

The results showed: i) a significant effect of temperature increase on clearance rate and toxin uptake, ii) no detectable time-related effects of toxic algal food on pre-ingestion sorting or on toxin profiles in oyster flesh, iii) either negative or positive effects of A. catenella concentrations on toxin uptake (“threshold” effect), iv) high amounts of toxins in the digestive gland, accounting for more than 80% of overall shellfish toxicity. The daily amount of toxins (Qtox) taken up by each oyster was evaluated by means of a global one-compartment model. However a two-compartment model finally gave the best match with real contamination kinetics, since it integrated both toxins sequestered in oyster tissues and toxins moving in through the digestive tract.

We adapted a visual census method, mainly used in demersal and reef fish studies, to characterize fish communities associated to drifting fish aggregating devices (FADs) in the Western Indian Ocean. Drifting FAD associated fishes from both equatorial (Seychelles) and tropical waters (Reunion Island) were examined by divers. A total of 32 species (belonging to 16 families) were observed associated with drifting FADs in equatorial waters, and 24 species (14 families) were found around FADs in tropical waters. Twenty species were found in both regions. The highest number of species observed at a single FAD was 18 (12 ± 2, mean±SD) in equatorial and 13 (10 ± 3) in tropical waters, not counting circumnatant species loosely associated with the FAD. Some species like Kyphosus vaigiensis, Canthidermis maculata, Elagatis bipinnulata, Acanthocybium solandri and Coryphaena hippurus were observed on all or most of the surveys. In this study, the contribution in biomass of the 18 common species associated with drifting FADs (but excluding circumnatant species), represents more than 98% of the biomass. The overall biomass values of closely associated species remains well below tuna biomass estimates for circumnatant tuna schools at FADs, estimated as high as 200 tons. The species that most significantly contribute to the by-catch in tuna purse-seines logically match those that showing the highest biomass values in our surveys (Carcharhinus spp., Elagatis bipinnulata, Coryphaena hippurus, Canthidermis maculata, and Acanthocybium solandri). One of the most abundant and ubiquitous species in our study was the spotted oceanic triggerfish Canthidermis maculata that sometimes formed massive schools of many thousands individuals around the drifting FADs. Future research is needed to explore the role of such non tuna species in the attraction and aggregation processes of tuna around drifting FADs.

The gilthead seabream is the most important Mediterranean aquacultured fish species. The main objective of this study was to investigate whether copper sulphate bath treatments used routinely in aquaculture have effects on important physiological functions of early life stages of the gilthead seabream (Sparus aurata). Fingerlings (80–90 days, 0.27 ± 0.06 g) were exposed to copper sulphate baths at 0, 0.25, 0.5 and 1.5 mg L−1 during 24 h. Effects on the central nervous function were evaluated analysing brain acetylcholinesterase activity (AChE). Oxidative stress was assessed by the quantification of lipid peroxidation (LP). Heat shock proteins (HSP70) were used as a general response to chemical stress, RNA/DNA ratio as an indicator of growth, and effects on detoxification function were estimated using glutathione–S-transferases activity (GST). Exposure of S. aurata fingerlings to copper sulphate induced increased lipid peroxidation. In contrast, there were no significant changes in AChE activity, HSP70 levels, RNA/DNA ratio or GST activity. Particularly, the absence of response in GST activity points towards a limited extent of the putative damage caused by the treatments at the highest doses (evidenced through the levels of peroxidation), since this enzyme is directly implicated in detoxification processes involving redox cyclic products. The results suggest that copper sulphate baths at the conditions tested are safe treatments for S. aurata fingerlings.

Quantifying of sediment reworking processes provides new insights into benthic ecosystem functioning of the Thau lagoon, an important European shellfish farming area. In order to evaluate bioturbation rates of surface sediments, profiles of 7Be (half-life: 53 days) and 234Th (half-life: 24.1 days) were measured in cores collected since December 2001 to December 2006. Several sites were selected to sample the diversity of the Thau lagoon: C4, T10, and T11 in the middle of the lagoon, C5, T7 and T8 nearby oyster farming, T2 and T4 in the western edge, T12 in the eastern part closed to industry. 234Th in excess (234Thxs; i.e. supplied to sediment by settling particles) and 7Be both show seasonal variations in activities and in penetration within sediment. Taking into account the moderate sedimentation rates of the Thau lagoon, sites (0.1–0.4 cm per year), the penetration of both short-lived radionuclides to variable depths, from 1 up to 8 cm, indicates efficient biological mixing of upper sediments. Bioturbation rates (Db) to the distribution of excess 234Th (234Pb-Db) and of 7Be (7Be-Db) range between 1 and 35 cm2 y−1, depending on site and season. Surface sediment mixing of the Thau lagoon is primarily controlled by the quality of particle input, i.e. the food supply to the benthic fauna, mainly governed by the hydrological and seasonal conditions. But locally shellfish production is a key parameter that influences bioturbation through biodeposition.

Diel, nocturnal and lunar input patterns of pre-settlement coral reef fish were described in Wallis, a typical high-island in the south-central Pacific, with a mid-size lagoon and a 2-m spring tidal range. Crest nets were set on the barrier reef to collect incoming pre-settlement fish. A diel input pattern was observed, with 82 to 99% of the larvae arriving at night. Nocturnal input of pre-settlement fish occurred throughout the night, at different times depending on the lunar phases. In contrast to studies done in other locations, the input was not higher during the first part of the night. The input level was related to moonlight and water level, but independent of tide direction. High input levels were recorded during all lunar phases, except the full moon. This lunar pattern differed from maximum settlement observed during the new moon in other locations. Consequently, a sampling strategy for studying temporal patterns of coral reef fish settlement in typical west Pacific high-islands should include new and quarter of the moon phases and should be extended to the entire night.

This work presents a method to observe pelagic fish around drifting fish aggregating devices (DFADs). A triple-frequency vertical echosounder was employed to observe fish distributions in the vicinity of DFADs. Surveys were conducted in a star pattern that was centred at the DFADs. The objective of the study was to define a methodology for future acoustic studies. This goal was pursued by (i) studying the spatial distribution of fish aggregations, (ii) developing concepts for the grouping of observed aggregations and (iii) developing specifications for future autonomous acoustic tools. For this purpose 5 cruises were carried out in the western Indian Ocean. The multi-frequency approach proved useful as a means of separating acoustic detections into sound-scattering layers (e.g. plankton and micronekton), fish aggregations and individual fish. Fish target strength (TS) was measured. Four types of aggregations were found near DFADs: (i) dense structure (ii) medium structure (iii) loose structure and (iv) structure consisting of separated targets. More than 90% of these structures were found within a radius of 400 m and about 75% within 200 m of the DFADs. The spatial configuration of DFAD fish aggregations appeared to be more dynamic compared to aggregations near moored FADs. The spatial distribution and structure of DFAD aggregations have direct implications for their catchability by tuna purse-seiner. We have carried out the first quantitative acoustic recordings around DFADs, and obtained a better understanding of the spatiotemporal dynamics of fish aggregations around DFADs in the Indian Ocean. Based on this knowledge we are now working on specifications for instrumented buoys that are intended as autonomous data recording observatories for such pelagic environments.

Interdecadal versus interannual time-scale variations of catch data of three anchovy fisheries distributed in the Humboldt Current System (HCS) were analyzed during the period 1960–2002, by using first a loess smoother. The loess residual data were considered as the interannual variation. Interdecadal changes were highly coherent for the three fisheries of anchovy distributed in the HCS, while there were differences in terms of interannual variations. The north-central Peru fishery was similar to the south Peru-northern Chile fishery in terms of the interannual component of fluctuation of these fisheries which was significantly and negatively related with El Niño-Southern Oscillations events occurring during the spring of the previous year. Interdecadal synchronous variations in the three anchovy fisheries suggest a common forcing by long-term environmental factors in the HCS, although other causes cannot be excluded. During the last 40 years, coherent changes in anchovy fisheries were observed, and this synchronous pattern is out of phase with large-amplitude sardine regimes. Long-term climate variability seems to be the main cause for interdecadal fluctuations in anchovy fisheries in the HCS, although available time series are too short to prove this link and exclude the hypothesis of nonenvironmental forcing. Large-amplitude regime shifts may be more important to consider than interannual changes since they can affect simultaneously and more dramatically the three anchovy fisheries distributed in the Humboldt Current System.

Seasonal changes in feeding habits and diet of the cockle Cerastoderma glaucum (Mollusca, Bivalvia) were analysed using carbon (δ13C) and nitrogen (δ15N) stable isotopes. I aimed to investigate the role of benthic and pelagic sources in the diet of this dominant infaunal bivalve on a western Mediterranean sandy bottomed pond. Adult C. glaucum and all potential organic sources (particulate and sedimentary organic matter, seagrass, macroalgae, heterotrophic detritus) were collected and analysed for δ13C and δ15N. In total 5 dominant organic sources were found, ranging between –21.0 and –8.0 ‰ for δ13C and from 3.0 to about 7.0% for δ15N. C. glaucum assimilated fraction ranged between –14.0/–15.0% and 6.0/9.0% respectively, for carbon and nitrogen, while its estimated fractionation seasonally varied between 1 and 1.5 for carbon and was about 3 for nitrogen. C. glaucum reflected the isotopic composition of its food while maintaining, throughout the year, a fairly constant isotopic composition in its assimilated fraction, despite the high variability in isotopic composition of available sources.

This study was designed to assess in situ the effects of sediment nearness on Crassostrea gigas metabolism. One year-old oysters were reared for 5 months (April-August) in plastic bags on metallic frames at 10 and 60 cm off the sediment at the beginning of April. The management of the energetic resources (storage, consumption) was estimated with respect to biochemical changes of proteins, lipids and carbohydrates. In order to evaluate the effect of the sediment nearness at cellular level, the metabolic rate was evaluated by assessing pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK) enzyme activities and electron transport system (ETS) activity. The metabolic pathways were assessed by measuring ATP and intermediary metabolites such as alanine, succinate and aspartate. Despite similar survival and growth at the two rearing levels, the protein, lipid and carbohydrate content were significantly lower in the oysters close to the bottom. In the oysters reared at 10 cm, PK activity was also significantly reduced and a significant negative correlation between alanine content and PK activity was revealed. The sediment nearness decreased significantly the ATP content in the oyster. There was a significant relationship between ATP and aspartate in these oysters. The use of aspartate contributed to complete the metabolic pathways along with carbohydrate allowing to maintain the same biological performance as the oyster reared far from the bottom. The energy state (proteins, lipids, carbohydrates and ATP contents) could suggest that the oysters close to the sediment were fed less but the metabolic enzyme activities allow to suggest an oxygen deficiency. However, the reduced PK activity, the absence of PEPCK activity stimulation and the utilization of aspartate suggest a transition stage to anaerobiosis.

From April 2003 to April 2004 monthly sea surveys were conducted around 2 fish aggregating devices (FADs) moored at 2000 and 2500 m depth in Martinique (Lesser Antilles). The use of a dual frequency splitbeam echosounder combined with an underwater camera and fishing methods allowed assessment of average space and time distribution of pelagic fish aggregated beneath the FADs, as well as identification of their overall size and species composition. At daytime, 4 fish aggregations were identified at each FAD, representing 4 distinct types: i) an aggregation of small juvenile tuna (mean fork length, FL: 30 cm) observed very close to the surface in 25% of daytime periods; ii) a small surface aggregation dominated by carangids, Caranx crysos, present in 65% of daytime periods; iii) a large sub-surface aggregation observed during all daytime periods: this aggregation appeared to be primarily comprised of 58 cm FL blackfin tuna (Thunnus atlanticus), mixed with yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tunas of the same size; and iv) sub-surface scattered large predators (mainly blue marlin, Makaira nigricans) present in 10% of daytime periods. A smaller sub-surface aggregation comprised of medium tuna mixed with “extranatants” (fishes which remain within 10 to 50 m of a FAD) was observed in 75% of night-time periods, whereas unidentified scattered fishes were detected from 70 to 400 m depth. The low daytime vulnerability of medium sub-surface tunas to applied line techniques leads us to assume that their feeding motivation was low during daytime. These tunas could preferentially feed on mesopelagic organisms during night-time and transition periods around Martinican moored FADs. Local fishermen mainly targeted the large scattered predators using very small tunas as living bait. The sub-surface tuna aggregation hence appeared to be currently unexploited by local fisheries, though it represented the large majority of the pelagic biomass around the moored FADs.

Anchovy and common sardine co-occur in the same reproductive and feeding habitat off central southern Chile (33°00'–41°20'S), and have a similar reproductive strategy. Egg-survey data from one survey carried out during the austral winter in 2005 were used to analyze the spawning spatial structure of anchovy (Engraulis ringens) and common sardine (Strangomera bentincki) through geostatistical techniques and generalized additive models. The spawning spatial structure of both species was characterized by a spatial autocorrelation intensity varying similarly with distance in all directions, ranging between 27.2 and 32.6 km for anchovy and common sardine, respectively. In average, egg density of anchovy was higher than egg density of common sardine, with the bulk of the spawning for both species located in the southern sector of the study area (38°S–40°S). In this sector, both species showed an overlapped distribution, and egg densities were mainly associated to shallow and coastal zones, suggesting that coastal shape and bottom depth are important factors for the spawning of both species. In the south sector, the egg density of both species was positively correlated, indicating that spatial structure of the spawning is not explained by a different strategy of space occupation among anchovy and common sardine.

The effect of short-time Artemia spp. feeding on growth performance and cumulative survival rate of barbel (Barbus barbus) larvae were studied under controlled aquaria conditions during the 21-day larval period. Three different diets (presenting reduced Artemia feeding) were tested for first exogenous nutrition of larvae (since 13 days post hatch): (1) artificial feed (Asta); (2) Artemia nauplii for 7 days followed by artificial feed; (3) Artemia nauplii for 14 days followed by artificial feed. The longer period of live food statistically improved growth of larvae (W = 174 ± 20 mg and SGR = 14.5 ± 0.5% d−1). The artificial dry food Asta without the addition of Artemia nauplii caused statistically decreased growth (W= 135 ± 22 mg and SGR= 13.1 ± 0.7% d−1). However, the growth of larvae with the short period of Artemia nauplii (W = 153 ± 25 mg and SGR = 13.8 ± 0.7% d−1) did not differ compared to either group. All used feeding diets did not have a significant effect on the cumulative survival rate of larvae ranging from 73 ± 1% to 74 ± 1% at the end of the larval rearing period.

The effects of the rearing environment on growth performance and survival rate of juveniles were tested under intensive controlled conditions in aquaria and troughs for 84 days following the larval period (from 34 to 118 dph). The environment of the troughs caused significantly decreased growth (W = 2079 ± 433 mg and SGR = 3.1 ± 0.05% d−1) of juveniles compared to ones reared in aquaria (W = 3236 ± 264 mg and SGR = 3.6 ± 0.1% d−1) at the end of the juvenile rearing period. Nevertheless, rearing environment did not have a significant influence on the cumulative survival rate of barbels (SC = 90 ± 4% and 81 ± 3% in aquaria and troughs, respectively).

In mainland Portugal, rays constitute an important by-catch of multi-gear shelf fisheries. However and despite their economical importance, landing information discriminated by species is scarce. The relative stability in Portuguese annual landings of rays and skates can be misinterpreted as no evidence for species declines. The present concern on the overexploitation of individual species arises from both theoretical considerations about biological and ecological traits and for historical reasons.

This work constitutes an approach for a retrospective analysis of ray landings in mainland Portugal. Data from research surveys carried along the Portuguese coast was used to infer possible changes in species composition on Portuguese landings. Clusters were determined based on data collected during surveys from species composition for three time-periods, 1989-1991, 1995-1997 and 2001-2003. The relative importance of the associate species within clusters was the input data to define discriminating rules posteriorly used to assign clusters to landings from each commercial vessel. The results show an increase of species relative importance and changes on species abundance: Raja brachyura and Raja clavata decreased, whilst Leucoraja naevus, increased. Furthermore, it was observed a decrease on the mean weight of the two first species and a relative stability in the last one. Such results reflect the importance of species life-history characteristics in particular, on the response to fishing impact.

The purse seine fishery in the Western Indian Ocean is dominated by Spanish and French vessels that rely heavily on the use of drifting fish aggregation devices (DFADs) to capture tropical tuna species (skipjack, yellowfin and bigeye tuna). This study uses local ecological knowledge (LEK) obtained through standardized interviews of fishing masters to compare and characterize the body of local ecological knowledge, fishing technology and fishing strategies of both fleets, with the goal of obtaining useful information for the management of the fishery. A notable difference between fleets was the number of DFADs actively monitored per vessel at any given time, which was much higher for Spanish vessels (ca. 60 versus 20 DFADs). Spanish vessels also achieved higher vessel CPUE (catch per DFAD set) than their French counterparts. The use of supply vessels to manage, monitor and protect productive DFADs, and the latest satellite-based technology to track and remotely monitor DFAD aggregations is restricted to the Spanish fleet. The French do not use supply vessels and deploy less sophisticated tracking buoys. These technological disparities resulted in some fishing strategy differences between both fleets, but few differences were found in the knowledge of tuna behavior accumulated by the fishers.

An histology and pathological survey on carpet-shell clam cultured in the south of Galicia (NW Spain) (Ruditapes decussatus) was carried out for a two years period (2000-2001). A temporal distribution of the potentially pathogenic agents were determined by histological analysis. In addition, stocks of molluscs reported to suffer mortalities during the studied period were also analyzed and the pathogenic burden determined. Pathogens do not follow a temporal pattern over studied period and no significant differences were detected nor on the presence nor in prevalence of these pathogens among all the analysed stocks. Therefore, no direct relationship can be established between infection by any pathogen and mortality episodes.

Multibeam omnidirectional sonars are tools currently used by fishers, but also allow the monitoring of pelagic fish schools surrounding a platform. Multibeam processing methods now offer improved capacities for raw data storage. The Simrad SP90 sonar was used for the detection of fish schools associated with drifting fish aggregating devices (FADs), and digital systems developed for the acquisition and processing of volume backscattering echoes and position data. Data sampling methods were defined based on two modes: one for periods searching for FADs and associated schools, and one for school monitoring in drifting mode. Validation of the detection of several FAD-associated schooling species was made by simultaneous visual observations or/and cross-checking with echosounder recordings. The characteristics of schooling behaviour in the targeted fish species are fundamental for the correct interpretation of acoustic data. Sonar detection threshold is the result of a compromise between fish number, size, species and the nearest neighbour distance (NND) of individuals per dynamic structure (school or shoal). Tuna schooling dynamics mean that NND can sometimes be too large to allow the presence of these fish to be detected, despite their number. Sonar data should be analysed and interpreted in a holistic manner, in combination with behaviour pattern and dynamics of all species around the drifting FADs. An autonomous sonar buoy prototype equipped with 360° scanning sonar coupled to video cameras will increase our understanding of tuna behaviour around drifting or anchored objects. A similar methodology can be applied to different kinds of platforms, either anchored or in permanent positions. This would improve the monitoring of fish schools around artificial reefs, open sea aquaculture farms, and across estuaries, channels or straits; applications which are undoubtedly essential for progressive fisheries management.