Mussel (Mytilus galloprovincialis) plasma contains cytotoxic activity against both vertebrate (erythrocytes and mouse tumour) and protozoan cells. Procaryotes (Escherichia coli and Vibrio alginolyticus) were not sensitive to the cytotoxicity. The activity was still present in dialyzed samples but was inhibited by heating at 45 °C. Large individual variability which was not correlated with protein concentration and an increasing number of reactive specimens following injection, suggested that naive mussels were in various stages of immune response. Purification by anion exchange chromatography followed by gel filtration revealed a 320 kDa cytotoxic polymeric protein that acts through a polymerization process after binding onto target cell membranes as revealed by ultrastructural observation.

European and Pacific oysters (Ostrea edulis and Crassostrea gigas) expressed antibacterial activity against both Gram negative and Gram positive bacteria which was most probably due to small proteins. When tested against the marine pathogenic Vibrio alginolyticus, hemocyte lysates of both species were more active than cell-free plasma. Antibacterial activity showed significant individual variability that was dramatically reduced by stimulation through mechanical stress or injection. The number of spontaneously active Pacific oysters increased from 50 to 100% following a single injection of bacteria.

These results strongly support the view that bivalve molluscs possess sensitive immuno-defense mechanisms that will greatly aid the development of aquaculture systems by employing refined techniques of transgenesis.

The structure of gonads and gametes is highly diversified in siluroid fishes; in some groups the testes are composite with an anterior part formed of spermatogenetic tissues and the posterior part of seminal vesicles which may or may not store spermatozoa. For catfish species of aquacultural interest, ovaries present the same general morphology as in other teleosts with oviducts. Spermatozoa are biflagellated in the Channel catfish (Ictalurus punctatus) and monoflagellated in the European catfish (Silurus glanis) and African catfishes (Clarias gariepinus, Heterobranchus longifilis). The egg size shows considerable intergroup differences, from 0.8–1.2 mm in some Pimelodidae and Clariidae up to 15–20 mm in Ariidae. In numerous cases, the eggs are adhesive and develop either a surrounding sticky layer (Ictalurus, Chrysichthys, Silurus) or an adhesive attachment disc (Clarias, Heterobranchus). Fertilization is in general external but internal fertilization is reported in some species. The annual sperm production was measured in European catfish and Channel catfish as 1.7 × 1011 and 1.8 × 1010 spermatozoa.kg-1 body weight, respectively. In females, the fecundity ranges from about 50 eggs per spawn in ariids up to more than 100 000 eggs.kg-1 body weight, e.g. in pimelodids and clariids. A large variety of controlled reproduction systems are found in the siluroids. In some cases (Ictalurus, Chrysichthys, Hoplosternum), spawning occurs naturally in ponds or tanks provided that adequate spawning substrates are available; fertilized eggs are collected immediately after spawning and placed into incubators until hatching. But for most species, although natural or semi-natural spawning could be achieved in captivity, the tendency at the present time is to develop techniques using hormonal-induced ovulation and artificial insemination in order to control the various steps of reproduction and to allow gamete preservation and manipulation. Oocyte maturation and ovulation or spermiation can be induced in many species by a large variety of hormones (GnRHs, fish gonadotropins, hCG, various steroids etc). Some information is available on gamete biology and preservation. Sperm motility is short-lived, not exceeding 70–80 s of forward movement as in most other freshwater teleosts. A peculiarity of the European catfish sperm is the activation by urine during sampling which could be prevented by direct collection in an immobilizing solution (NaCl 200 mM, Tris HCl 30 mM, pH 7.0). Spermatozoa cryopreservation was successfully attempted in several species. Ova generally survive only a few hours after ovulation and fertilization must be carried out soon after. Methods for gamete collection, insemination and incubation of eggs are described for the most widely cultured siluroid species.

Quelques aspects de la reproduction du listao (Katsuwonus pelamis) dans deux zones distinctes de l'ouest de l'océan Indien ont été étudiés de février 1989 à février 1994. A partir d'échantillonnages faits, soit à bord des thoniers senneurs sur du poisson frais (1 656 individus), soit à la conserverie de Maurice sur des thons décongelés (4 152 individus), les différents stades du cycle sexuel ont pu être précisés. La taille de première maturité sexuelle est atteinte à 41–42 cm (longueur à la fourche) chez les femelles et à 42-43 cm chez les mâles, correspondant à des individus âgés d'environ 1,5 an. L'évolution mensuelle de la proportion des différents stades macroscopiques de maturation des gonades montre que, quel que soit le mois considéré, il y a toujours plus de 70 % des femelles échantillonnées qui présentent des ovaires en fin de maturation (stade IV). Les variations du rapport gonado-somatique (RGS) montrent que la reproduction du listao a lieu toute l'année mais qu'il existe cependant plusieurs périodes d'activité sexuelle plus intense. L'observation histologique de 737 ovaires indique la présence de follicules post-ovulatoires (indicateur de ponte récente) pendant les 2 périodes de mousson, mousson de nord-ouest (novembre à mars) et mousson de sud-est (juin à août) tandis que la proportion d'ovaires présentant des follicules atrétiques est maximale aux 2 périodes d'inter-mousson (avril-mai et septembre-octobre). L'étude du sex-ratio montre que. pour l'ensemble de la période d'étude et pour les deux zones considérées, la proportion de mâles est significativement supérieure à celle des femelles. Ses variations mensuelles semblent indiquer une accentuation de la prédominance des mâles à chaque période de ponte plus intense.

Heritability of larval growth rate in diferent food environments and genotype-food environment interaction (during larval growth) are estimated in Mytilus chilensis, based on a nested design, involving 24 full-sib families (8 males each mated to 3 separated females) grown under three different algal concentrations. The heritability estimates for larval shell length ranged between 0.2 ± 0.1 and 0.9 ± 0.3 and showed a decreased towards the low food treatment; but the values suggest that selection would be effective. However, since there is a significant genotype-food interaction, selection should be done in each environment in which the animals are expected to perform. The significant interaction term (p<0.001) associated with a significant genetic variability for larval growth suggest the presence of genes in the population whose expression depends upon local food conditions.

Atlantic salmon, Salmo salar, and several species of whitefish, Coregonus nasus, C. peled, C. Lavaretus baeri, males were treated with a long-acting medical androgen preparation - "Testoenatum". This preparation contains 24 mg of testosterone enanthate and 111 mg of testosterone propionate in 1 ml peach oil solution. Multiple (2–5) or single intraperitoneal injections of a standard dose (0.1 ml/kg fish body weight) were used. Treatment performed shortly before the beginning or within the breeding season resulted in a significant stimulation of spermiation, improvement of sperm parameters and extention of the gonad functional maturity period for 1–4 months. Low water temperatures (0.5–l.0 °C) seem to be essential to obtain a long-lasting effect after one injection. The histology of the pituitary gland suggests that the gonadotropic cells were activated through a positive feedback mechanism. Testoenatum suppressed Sertoli cells' phagocytary activity.

Successful rearing of hatchery-reared sea bass, Lates calcarifer, fry in illuminated floating cages was demonstrated in a 42-day experiment. Three feeding regimes, i.e. natural zooplankton (NZ) + minced fish flesh (MFF), NZ alone, or MFF alone and two stocking densities (600 and 1 200 individuals m2) were tested in a 3 × 2 factorial experiment. Fish reared in unlit cages and fed MFF alone during daytime served as the control. Results showed that no interaction existed between stocking density and feeding regime and that the two stocking densities used did not influence fish growth in terms of mean final body size. In general, sea bass reared in lit cages (NZ + MFF and NZ) grew and survived better than the control fish (MFF). However, fish reared under NZ + MFF feeding regime had the highest final mean total length (TL, 42.1 mm) and body weight (BW, 1 311.8 mg) followed by fish reared under NZ feeding regime (mean TL = 26 mm, BW = 415 mg). Fish in the unlit control cages exhibited the poorest growth (final mean TL and BW: 26 mm and 277.6 mg BW). Furthermore, specific growth rates (range: 5.7–8.5% day−1) of fish in lit cages were significantly better than those of fish in the unlit control cages (mean: 3% day−1). Percentage survival (38%) of fish stocked at 600 m−2 density and fed NZ was not significantly different from fish in the NZ + MFF feeding regime. However, increasing the density to 1 200 ind. m−2 tended to significantly decrease percentage survival (20%) of fish with NZ feeding. Fish reared in the unlit control cages had the poorest survival of 13–14%. The high percentage composition by number (CN, 88%) of copepods in the stomachs of sea bass fry fed on NZ alone and the equally high percentage feeding incidence (94%) indicated that fish fed sufficiently on natural zooplankton. Supplemental feed using minced fish flesh contributed about 43–59% of the fish diet in addition to natural zooplankton.

Several virulence factors involved in the potential pathogenic capacity of Vibrio P1, the causative agent of brown ring disease (BRD) affecting cultured Manila clam adults (Ruditapes philippinarum), have been evaluated in comparison with other strains of several Vibrio species isolated from diseased clams. The importance of bacterial cell surface associated properties as virulence factors has been studied considering both non-specific and specific bacterial adhesion to clams. Vibrio P1 showed moderate hydrophobicity, but high affinity to bind to Congo Red dye and the presence of appendages, characterized as fimbriaeor pili. All the strains of Vibrio P1 secreted haemolysis and cytotoxins, and were also strong exotoxin producers. The presence of a large 49.2-MDa plasmid in all the strains of Vibrio P1 may be used as an epidemiological marker, but its involvement in pathogenic mechanisms has not yet been established. Although in some Vibrio strains, iron-acquisition systems play an essential role in their pathogenicity, they do not seem to be an important factor in Vibrio P1, since this pathogen lacks siderophore-mediated iron transport mechanisms.

Pour décrire la cinétique de l'ovogenèse et la stratégie de ponte chez la limande, Limanda limanda (L., 1758) les ovaires de 74 femelles capturées en baie de Douarnenez et en baie de Seine en 1990 et 1991 ont fait l'objet de prélèvements. Une échelle de développement ovocytaire en six stades a été utilisée pour classer les ovocytes. L'apparition d'alvéoles corticaux à la périphérie du cytoplasme est le premier signe de la vitellogenèse. Ils sont visibles dans les ovocytes dont le diamètre est de 120 μm, taille limite à utiliser lors d'études de la fécondité. Chez les femelles à ponte précoce un hiatus existe avant les pontes entre les ovocytes prévitellogéniques et vitellogéniques. Ceci permet de classer la limande parmi les espèces à fécondité déterminée. Chez ces femelles l'intensité de l'atrésie est faible et leur fécondité annuelle est proche de la fécondité potentielle. Par contre chez les femelles à ponte tardive tous les ovocytes vitellogéniques ne parviendront pas à maturité et ceux non encore émis à la fin du printemps dégénèreront.

The genetic characterization of catfishes by means of phenotypic markers, karyotyping, protein and DNA polymorphisms contributes to or forms an integral part of the disciplines of systematics, population genetics, quantitative genetics, biochemistry, molecular biology and aquaculture. Judged from the literature, the general approach to research is pragmatic; the Siluroidei do not include model species for fundamental genetic research. The Clariidae and the Ictaluridae represent the best studied families. The systematic status of a number of species and families has been either elucidated or confirmed by genetic approaches. Duplication of ancestral genes occurred in catfishes just as in other vertebrates. The genetic structure of and gene flow among natural populations have heen documented in relatively few cases, while the evaluation of strains for aquaculture (especially Ictaluridae and Clariidae) is in progress. The mapping of genetic markers has started in Ictalurus.It appears that a more detailed knowledge of catfish populations is required from two perspectives. First, natural populations which are threatened by habitat loss and interfluvial or intercontinental transfers are poorly characterized at the genetic level. Secondly, the selection of suitable strains for aquaculture should be encouraged. Implementation should pose no problems given the present powerful means, such as DNA characterization combined with protein polymorphisms and phenotyping, to solve the above-mentioned issues.

The effectiveness of different gonadotropin releasing hormone analogues (GnRHa) and/or pimozide for inducing ovulation in Arctic charr was investigated at two different temperatures: 5 °C, a temperature suitable for spontaneous ovulation in Arctic charr and 10 °C, a temperature which inhibited ovulation in Arctic charr. At 5 °C all the different GnRH analogues tested were able to induce and synchronize ovulation. At 10 °C a sustained release preparation of D-tryptophan6 luteinizing hormone releasing hormone (D-Trp6LH-RH) at 20 μg.kg−1 and an acute release preparation of D-arginine6salmon GnRH (D-Arg6 sGnRH) at 100 μg.kg−1 were able to induce ovulation in 80% of the females within 15 days (versus 2% in controls). Pimozide alone or in combination with a low dose of D-Arg6sGnRH was able to induce some ovulation at 10 °C, suggesting that a dopamine inhibition of gonadotropin secretion could occur at 10 °C. Egg survival in groups receiving GnRHa at 5 °C was comparable to controls (73%) except in the group receiving GnRHa in combination with pimozide (45%). At 10 °C, egg survival was significantly lower than controls at 5 °C, except for the group receiving pimozide alone. At both temperatures, egg survivals of each spawn were negatively correlated with the plasma gonadotropin (GtH2) level of the reproducing females except in groups receiving a sustained release preparation of D-Trp6LH-RH.

Tilapia cameronensis fry were reared in plastic tanks and earthen ponds at the Fishculture Research Station, Foumban, Cameroon. Their growth rate was compared to that of the Nile tilapia (Oreochromis niloticus) fry, reared under identical conditions. Different treatments were applied (food or organic manure only; food combined with organic manure); physical-chemical variables were quantified. The best growth rate was recorded for fry reared in tanks receiving both food and organic manure: the daily weight gain of T. cameronensis fry in tanks was nearly half of that of the Nile tilapia, while in ponds T. cameronensis showed a higher growth rate than O. niloticus (0.19 g.d−1 versus 0.13 g.d−1). The growth rate decreased with increasing stocking density. In another experiment Tilapia cameronensis fry were reared in aquaria at different stocking densities in a recirculated water system. The highest growth rate was recorded for fry stocked at 0.5 fish.l−1 and receiving daily a feeding rate of 15% of the total biomass. This growth rate was comparable to that of fry stocked at 0.25 fish.l−1 receiving the 5% feeding rate. The latter had the lowestFCR. Mortality due to aggressive interactions increased with decreasing stocking density.

Adult, healthy Manila clams, Ruditapes philippinarum, were inoculated in the laboratory with different, possibly pathogenic bacteria species to study the cellular immune responses. Challenging the clams with Vibrio P1, the causative agent of brown ring disease, induced significant increased total hemocyte counts three days post-challenge. The triggering role of the number of bacteria in the inoculum suggested a threshold for inducing the host response. In addition, a significant decrease of hyalinocytes and an increase of granulocytes revealed a modification in hemocyte population balance. No response was observed in individuals that received either heat killed-Vibrio P1, V. anguillarum or V. pelagius. These experiments demonstrate in R. philippinarum the influence of bacterial parameters on the selective induction of host immunodefence mechanisms. The biological processes by which intra-pallial inoculation of Vibrio P1 stimulates the internal defence system of the host has not yet been identified but the role of some bacterial factors (toxins, adherence capacity) is discussed.

Selection, hybridization, and genome manipulation in the Siluroidei is reviewed. Selection topics include strain evaluation, qualitative traits, quantitative traits, mass selection, family selection, inbreeding, and crossbreeding. Hybridization is discussed with reference to culture traits. Genome manipulation technologies-sex reversal, gynogenesis, androgenesis, polyploidization, and gene transfer-are considered with application to genetic improvement of Siluroidei. Strains of ictalurid catfish Vary significantly for traits such as growth, disease resistance, harvestability, reproduction, body conformation and carcass yield. Growth of domestic strains can be 250% greater than that of wild strains. Strain differences have also beenidentified for clariid, bagrid, and silurid catfishes. Mass selection has increascd growth rate by up to 30%. Heritability estimates predict a response to selection for the traits of disease resistance and tolerance to low oxygen levels. Crossbreeding strains of Ictalurus punctatus have improved growth, disease resistance and reproductive performance. Two generations of inbreeding depressed body weight of I. punctatus as much as 30%, and can reduce viability and reproductive performance. Hybridization of I. punctatus X I. furcatus has resulted in a 20% increase in growth. Traits for tolerance to oxygen deficit, feed conversion, disease resistance, harvestability, and carcass yield were also improved. Interspecific, intergeneric, and interfamilial hybrids have been made with clariid fishes; heterotic growth was indicated. Hybridization has also been used to combine desirable traits of parental species. Sex reversal of I. punctatus using estrogen treatment followed by progeny testing can result in monosex, all-male populations. Gynogenesis and androgenesis are approaches to production of inbred lines of catfish, but thus far have limited application in aquaculture. Polyploidization has been applied in several ictalurid, silurid, and clariid fishes, but predicted improvements in performance have not been realized. Gene transfer has been accomplished in I. punctatus and Clarias gariepinus using microinjection and electroporation; the foreign genes have been expressed and inherited. Transgenic I. punctatus containing salmonid growth hormone genes grew 20–40% faster than controls.

Manila clams, Tapes philippinarum (Adams and Reeve) are cultivated beneath plastic netting, to protect them from excessive predation, and harvested after approximately two years. Both the on-growing and harvesting process have the potential to alter benthic communities. In order to study these effects, we surveyed a clam lay and uncultivated areas at a site of commercial clam cultivation in south-east England. Surveys were undertaken at the end of the growing stage, immediately after harvesting by suction dredge and seven months later. Infaunal abundance was greatest within a net covered clam lay than in proximate and distant control areas, but the total number of species encountered was similar in all areas (20–22). These differences were not attributable to variation in sediment structure or environmental variables between the areas sampled. Tube-building polychaetes, such as Lanice conchilega and Euclymene lumbricoides, were particularly abundant within the cultivated area as was the errant polychaete, Syllis gracilis. Harvesting by suction dredge altered sediment composition by removing the larger sand fractions down to the underlying clay substratum, consequently there was a large reduction in the density of all individuals and the total number of species. Seven months later, no significant difference was found between the infaunal community in the harvested clam lay or either of the control areas and sedimentation had nearly restored the sediment structure. These observations indicate that the practice of clam cultivation does not have long-term effects on the environment or benthic community at this site.

Juvenile oyster disease (JOD) in the eastern oyster, Crassostrea virginica, is characterized by a conchiolin deposit on the inner surface of the valves. Similarities to pathological syndromes affecting other oysters (pearl oyster mortality) and clams (brown ring disease), has suggested an infectious origin and a possible bacterial etiology. Bacteriological analysis (Total Heterotrophic Bacteria, THB and Total Vibrio sp., TVS) of oyster soft tissues, shell fluid and inner shell surfaces were monitored during the course of JOD onset and development. A significant increase in THB (but not TVS) occurred in shell fluid and at thesurface of the inner shell of JOD affected oysters. At the same time, changes in cytometric parameters (Total Hemocyte Counts, THC; Differential Hemocyte Counts, DHC) in hemolymph and shell fluid were documented in symptomatic oysters. THC in the shell fluid showed a decrease in late-stage JOD oysters. The disease was also correlated with altered cell ratios in both hemolymph and shell fluid, resulting in an increase in the percentage of the granulocytes in both locations. Our results have showed that main pathological changes associated with JOD occurred in extrapallial region rather than in the soft tissues. The disease was transmitted in the laboratory by extracts from diseased oysters: anomalous conchiolin developed within 4 weeks and the prevalence was higher when two inoculations were performed rather than one. A number of bacterial strains were found at high levels in diseased oysters and isolated. However, none produced the JOD deposit when injected into asymptomatic oysters. The bacterial etiology hypothesis for JOD should be explored further, expanded beyond the family Vibrionaceae, and should include consideration of a multiple etiology.

Pacifastacus leniusculus has established hundreds of breeding populations in Britain since its introduction in 1976. One such population was established in the River Great Ouse, a major lowland river in mid-to eastern England, from 140 crayfish introduced in 1984. Estimates of growth, density and biomass of the population in 1992 are presented. Under laboratory conditions, the per moult increment (MI) and percentage per moult increment (PCMI) of crayfish were binomially correlated to their carapace length (CL), that is, the MI increased with CL and then decreased as crayfish grew old, and the PCMI decreased with increase in CL. Based on length frequency distribution data collected from the river in October and November and estimated by Bhattacharya's method, seven male cohorts while only four young female cohorts were identified because of insufficient data for old cohorts. The mean CL of each crayfish cohort was 16.6, 31.2, 41.6, 52.0, 57.8, 64.2, and 69.2 mm for 0+ to 6+ year old males respectively, and 15.4, 28.5, 39.7, and 49.8 mm for 0+ to 3+ females. There were no significant differences between growth rates of either CL or WW of males and females at age for 0+ to 3+ (no data of females > 3+ were available for comparison).

In a riffle, the densities and biomass of crayfish were significantly different between four domains with different bottom substrats and highest in the habitat with the highest density of cobbles and thus, greatest density of potential shelters. The mean densities and biomass of crayfish of all sizes in this riffle were between 10.m2 and 61 g.m−2 respectively in July and 15.m−2 and 53 g.m−2 in November. In a pool, mean density and biomass of crayfish > 30 mm CL, estimated by Fish-Ford multiple capture-mark-recapture methods, were 0.8 m−2 and 37 g.m−2 between May and August.

The channel catfish (Ictalurus punctatus) is the most widely cultured foodfish in the U.S., thus most of the nutrient requirement data are available for this species. Qualitatively, about 40 nutrients have been identified as necessary for the normal metabolic function of the channel catfish with quantitative requirement values available for about 30 nutrients including amino acids, fatty acids, minerals and vitamins. Additional information is available on protein and energy requirements, digestible protein and energy coefficients as well as amino acid availability values. Thus adequate nutritional information is available to formulate high quality practical channel catfish feeds.Only limited nutrient requirement data are available for the other Siluroidei species. Some requirement data have been reported for a few species from Africa (Clarias gariepinus, C. isheriensis, Heterobranchus longifilis and H. bidorsalis), Asia (Clarias batrachus, C. macrocephalus, C. fuscus and Heteropneustes,fossilis) and Europe (Silurus glanis). The available requirement data will be summarized and compared with the requirement data for the channel catfish. Some variation does appear to exist in optimum dictary protein levels, essential fatty acid requirements, and lipid vs carbohydrate utilization.

Les Siluroidei sont connus pour avoir, en milieu naturel, une activité trophique essentiellement nocturne. Ceci a été confirmé au cours d'expériences réalisées en conditions d'accès constant à une source de nourriture, ou encore à l'aide de distributeurs d'aliments à la demande. Cependant, en conditions limitantes en température ou en oxygène, l'activité trophique de certains Siluroidei devient dépendante de ces deux facteurs, et n'est plus synchronisée par l'alternance jour/nuit. Le rythme nycthéméral d'activité trophique des espèces étudiées présenterait donc une acrophase préférentiellement nocturne, mais posséderait une certaine plasticité. L'existence d'un contrôle d'origine endogène de ce rythme est aussi discuté. Rares sont les poissons Siluroidei qui refusent de s'alimenter lors de distributions diurnes d'aliments. Il convient d'évaluer les conséquences que pourraient avoir sur la croissance des horaires d'alimentation non synchrones avec les rythmes alimentaires. L'effet de l'heure des repas sur les performances de croissance montrent une tendance générale à une croissance supérieure chez les animaux nourris de nuit par rapport aux animaux nourris de jour. Cependant, le mode de distribution choisi (en repas ou en continu) semble avoir plus d'influence que l'heure de distribution sur les performances de croissance. Certains auteurs ont aussi montré une augmentation de l'adiposité des poissons lorsqu'ils n'étaient pas nourris en phase avec leur rythme alimentaire.

Cette étude d'écophysiologie a été réalisée sur l'huître japonaise (Crassostrea gigas) cultivée en baie de Marennes-Oléron (France) en mai 1992. Les mesures sont effectuées dans des conditions alimentaires naturelles au cours de trois cycles de mesure (a, b, c) à des coefficients de marée de 49,57 et 88. La matière particulaire totale est mesurée en continu durant les cycles de marée. La fonction de consommation est calculée selon une nouvelle formulation prenant en compte un "échappement particulaire" précédant le tri pré-ingestif et représentant une perte passive de particules de petites tailles entraînées par la masse d'eau à travers le filtre branchial. La comparaison des fonctions de consommation et d'absorption de la matière organique totale et de la chlorophylle a, montre des différences significativement supérieures pour la charge particulaire de 55 mg.l−1 (c) comparée aux autres conditions (a, b) de charges particulaires inférieures à 30 mg.l−1. La comparaison des coefficients de sélectivité et des taux d'absorption de la chlorophylle a, (43,3 et 81,6 %), respectivement, supérieurs à ceux de la matière organique totale (33,4 et 68,7 %),respectivement, montre le tri de la matière organique effectué par l'huître. Le bilan énergétique calculé prend en compte le matériel d'origine phytoplanctonique et le matériel organique total. Les potentiels de croissance ainsi obtenus de 0,88-11,60 et 47,60 J.h−1.g−1 respectivement pour les conditions à 13,5–28,9 et 54,6 mg.l−1 de charge particulaire totale, traduisent une forte variabilité journalière d'énergie disponible pour la production organique dans le milieu naturel. Ces résultats sont cohérents avec les résultats de croissance d'huîtres en élevage dans la baie de Marennes-Oléron.

An image discrimination technique was developed to improve specific identification of some toxic Dinophysis cells (marine dinoflagellates involved in diarrhoeic shellfish poisoning), especially the "acuminata" and "sacculus" groups, which can be present at different ratios in natural sea-water samples collected during toxic episodes. This work was performed with image analysis software SAMBA (TITN Alcatel) using preserved cells directly observed through an inverted microscope and recorded with a video camera before further processing. All morphometric parameters used for discrimination of 7 different species or morphotypes of Dinophysis were tested with discriminant analysis. This study indicates that Dinophysis sp. and D. pavillardi seem well classified at the species level, whereas D. cf. acuminata and D. sacculus appear to be morphotypes of D. acuminata.