La tolérance aux basses températures des gamétophytes de l'algue alimentaire Undaria pinnatifida est examinée selon différentes méthodes de cryoconservation. La conservation à -80 °C dans une solution glycérolée à 28 % et celle à −196 °C dans une solution en eau de mer de glycérol à 5 ou 10 % ne permettent que des survies de, respectivement, 9 et 4 jours. Par ailleurs, la viabilité n'est pas affectée par un refroidissement de 5 °C/min et une conservation de 15 minutes à −15 °C sans milieu de cryoprotection mais est fortement diminuée par un stockage de 15 minutes à −30 ou −196 °C, même en présence de DMSO. La réduction de la survie des gamétophytes se traduit morphologiquement par une dépigmentation et/ou une contraction des cellules.

In Amazonian fisheries, the silver arowana, Osteoglossum bicirrhosum (Cuvier 1829) is heavily exploited for human consumption as an adult, and for the aquarium trade as a small juvenile (yolk sac juvenile mainly). The periodicity of annuli formation on otoliths and growth variability of the silver arowana were studied in different river river-basins of the Peruvian Amazon between 2006 and 2009. Transverse stained sections of 606 individual otoliths were analysed from four different river-basins, the Amazonas, Ucayali, Napo and Putumayo, of which 554 could be interpreted. These belonged to 274 females ranging from 15 to 91 cm (standard length) and 280 males ranging from 30 to 91 cm. In addition, yolk sac juveniles of known age were collected to improve growth modelling. Monthly proportions of stained otolith edges validated the formation of a single annulus per year in two different river-basins with lagged hydrological cycles: the Amazonas-Ucayali and the Putumayo. Stained growth mark counts resulted in a longevity estimate of at least 16 years for the silver arowana in the Peruvian Amazon. This fish grew quickly during the first two years, and asymptotic growth was reached after four to five years, except in the Putumayo where it was reached slightly earlier. Results showed no significant growth dimorphism between sexes within basins, but indicated significant growth differences among river basins. Silver arowanas measured, on average, between 38 and 40 cm at the end of their first year. Length-at-age differences among river basins increased with age to reach over 14 cm (and >3 kg) after 7 years between the faster and slower growing populations (Amazonas and Putumayo, respectively). The growth differences observed emphasize the need for further investigation on the population structure of this species as, although these differences might merely be phenotypic responses to contrasted environmental conditions, they could alternatively reflect the existence of several populations with distinct genetic and life history characteristics. The consequences of such differences would be very important for the management and conservation of this fragile and extensively exploited species.

The aim of this project was to evaluate the impact of probiotic (Phaeobacter gallaeciensis, X34 strain) treatment on the complete development (from veliger to metamorphosis) of Pecten maximus larvae in the context of a bacterial challenge and in conditions more representative of hatchery practices. To that effect, the present study was divided into two main steps. In the first, we used in vitro analyses (antibiograms and microplate assays) to validate the inhibition abilities of X34 on the growth of four Vibrio pathogen species. During the second step, we added pathogens (Vibrio pectenicida) into rearing tanks after two weeks of pre-treatment with the probiotic and then followed the larval development of Pecten maximus through the monitoring of survival rates, shell lengths and metamorphosis ability. Moreover, antioxidant (catalase and superoxide dismutase) and lipids peroxidation activities were also measured after bacterial challenge in order to evaluate the physiological response of larvae to pathogen exposition. Our results indicated an activation of the two selected antioxidant enzymes after bacterial challenge, but the increase was significantly lower in probiotic treated larvae. At the end of the experiment, the strain X34 treatment prevented a mass mortality event and showed a significant increase in the number of individuals reaching competence, when compared to untreated larvae.

Using catch composition data collected on individual fishing trips between 1990 and 2001, we study fishing tactics and strategies of the coastal demersal trawlers operating in Senegal. Types of fishing actions (tactics) are defined through catch composition on fourteen stocks. Types of fishing units (strategies) are defined according to the tactics they can use. These two typologies are built using the K Means method, a non hierarchical classification approach. As results, twelve tactics and six strategies are primarily identified. Using expert knowledge some fishing tactics are gathered and eight tactics and five strategies are finally considered and discussed with a presentation of the articulations between stocks, tactics and strategies.

L'estimation de l'âge de Prochilodus nigricans Agassiz, 1829 est réalisée à partir de 840 poissons pêchés de 1983 à 1987 dans les principaux milieux du réseau hydrographique de la rivière Mamoré (Béni, Bolivie). Diverses préparations et observations de pièces calcifiées (écailles, otolithes, rayon épineux dorsal et os operculaire), ainsi que les comparaisons de plusieurs lectures, ont permis de choisir l'écaille et ses marques de croissance pour estimer l'âge. Les pertes d'écailles, entraînant la présence de très nombreuses écailles régénérées macrocentriques, paraissent dues à l'abondance des poissons lépidophages du genre Roeboides. Les marques principales de croissance sur les écailles microcentriques sont décrites, ainsi que les principales anomalies ayant engendré des difficultés de lecture. La validation des marques retenues est faite directement par la mesure de la distance séparant la dernière marque du bord de l'écaille, et indirectement, pour les jeunes nés dans l'année, par la comparaison de leur distribution de longueurs à la capture avec celle obtenue par rétrocalcul au moment de l'apparition de la première marque, Pour tous les groupes d'âge, la formation des marques principales de croissance sur les écailles est influencée par le niveau des eaux dans le Mamoré : la formation des annulus se produit une fois par an lors de l'étiage ou au début de la crue (septembre à décembre), sur une grande majorité des individus. La date moyenne de naissance étant fixée au 15 février, l'âge peut étre connu en général avec une précision de l'ordre du mois. Pour l'étude de l'âge chez une espèce inconnue, le choix préliminaire du type de pièce à prélever est orienté â la fois par les résultats des tests de lectures comparées et par des considérations pratiques.

Dynamic aspects of an asynchronous cyprinid's ovogenesis, the gudgeon Gobio gobio L., were examined by a histo-morphometrie approach and effects of two factors, temperature and photoperiod, were investigated in respect to the stage of maturation. Four stages of maturity (one protoplasmic or vacuole free oocyte, two vesicle stages, also called in endogenous vitellogenesis and one vitellogenic or in exogenous vitellogenesis) were identified and compared to macroscopic characteristics of maturity (gonadosomatic index and condition coefficients, K and K 1). Growth and relative proportion to the entire ovary of each oocyte stage was measured on the different experimental groups. Relative importanee of temperature and photoperiod were clearly dependent on the gametogenic stage (recrudescence, final maturation and ovulation, and regression). Under constant temperature and photoperiod conditions, a strong vesicle stage oocyte regression was observed; a periode of low temperature or decreasing photoperiod seemed necessary to allow gonad recrudescence to be initiated. An annual cycle contracted into 6 months accelerated gametogenesis and produced off-season spawnings. Contraction of the reproductive cycle did not entail a rduction of oocyte growth or the yolky oocyte proportion. During the spawning period, females ovulated several times with a 15-day interval between successive spawnings. Vesicle and globule stages were induced by increasing temperature or photoperiod, but final maturation and ovulation were primarily dependent on temperature. The regressive stage was caused by a decreasing photoperiod and/or temperature. From a group synchronous distribution of oocytes at the start of recrudescence, the gudgeon's ovary changed to a totally asynchronous distribution at the end of vitellogenesis.

Based on the discrete optimal choice theory and a random utility model (RUM) framework, this paper focuses on the firm's long-term choices. A behavioural study on the stay and exit decisions of the fishing firms belonging to the inshore fleet of the Basque Country is undertaken by estimating a logistic model from a set of socio-economical sample panel data for the period 2003-04. Specifically, we aim to determine the set of vessels', skippers' and economic variables that may influence the probability of a fishing vessel to exit from the fishing activity. Special attention will be paid to the roll that incentives generated by decommissioning grants play in the fishermen's long-term behaviour. Our results indicate that the owner's age, years of experience being a skipper, the arrangement of continuity in the familiar business, the degree of dependency upon bank loan and lastly but not least decommissioning grants may significantly determine the decision to abandon the activity.

Levels of muscle and liver adenylates, phosphocreatine (PCr), total adenylates (TA) and the adenylate energy charge (AEC) exhibited significant seasonal changes. Fish size and condition factors were significantly different throughout this study; however there were no correlations between fish size or condition factor and metabolite levels. Muscle adenosine triphosphate (ATP), TA and AEC were lowest in winter and positively correlated with temperature; while adenosine diphosphate (ADP) and adenosine monophosphate (AMP) levels were high in winter and negatively correlated with temperature. Muscle AEC's dropped into the stressed range (0.5–0.75) during winter months. ATP/ADP ratios were lowest while PCr/ATP ratios were highest in winter months; indicating that a capacity for phosphate buffering existed and could not account for these low muscle AEC's. Liver ATP, TA, PCr, AEC, and adenylate ratios were lowest in the spring and were not correlated with temperature, but rather coincided with reproduction. Liver AEC's dropped into the lethal range (<0.5) in April; although no fish mortalities were observed. Liver AEC's were lower than muscle AEC's throughout the study. The AEC appears to have some validity as a long-term indicator of physiological status and may have application in monitoring/predictive programs due to its predictable response to seasonal change. However, cautious use is suggested until temperature effects on adenylate metabolism and seasonal effects on metabolic recovery following capture stress can be established.

Small-scale fish farming in tropical Africa is mainly based on pond culture of Nile tilapia Oreochromis niloticus with supplementary organic fertilisation. Until recently, the ‘high’ stocking densities practised (2 fish·m–2) led to stunted populations and very low yields. Since 1996, rural fish farming developed significantly in Côte d’Ivoire. Only a dramatic decrease in stocking densities allowed fish farmers to produce marketable-sized tilapia with reasonable yield in extensive culture. Density control is achieved through tilapia monosex male culture and stocking the predator Hemichromis fasciatus. Further development of low-input tilapia farming requires improvement of production results. A growth model based on maximal growth and ingestion, maintenance needs and efficiency of food for growth was developed to explain and help optimise production results. The model was validated with farm and experimental data and demonstrated that, for a given rearing period (from 30–50 g fingerling, to market-size), yield increased with density, but then decreased beyond an optimal density. When market-weight target is set, the same variation of yield according to stocking density is observed. Densities of 2 to 3 fish·m–2 markedly reduce tilapia yield in extensive culture. Moreover, increasing market weight from 150 to 450 g·fish–1 will only induce a limited decrease in maximal yield (around 20 %) if the density is lowered and the rearing period lengthened. This decrease is more than compensated by the higher price of large tilapia. Using rearing cycle data, the model can predict the results of alternate combinations of stocking density and duration of rearing period under the same pond management. Thus, production results can be optimised given the objectives and constraints of each fish farmer. This model is a valuable tool to develop extensive tilapia farming in tropical areas, and raises questions for researchers.

Implementing the Ecosystem Approach to Fisheries is a demanding exercise even though a more or less sophisticated approach might be adopted depending on the fishery or problem concerned and on the capacity available to deal with it. In France, DEMOSTEM, a programme of Ifremer was established to try to practically apply the EAF principles across the high diversity of situations existing in the country. The article summarizes very briefly the lessons learned through this programme implementation and some of the key findings and outcomes. In conclusion, it offers some perspectives on the whole process.

In the south-west lagoon of New Caledonia, the first sexual maturity size is 45 mm for Annachlamys flabellata (Bernadi), 60 mm for Comptopallium radula (L.) and 50 mm for Mimachlamys gloriosa (Reeve). The global sex-ratio was not significantly different from 1:1 for C. radula unlike A. flabellata andM. gloriosa (1.3:1 for two species). The significantly greater mean size of females suggests a protandric sex reversal. The reproductive cycle was studied monthly for two years for M. gloriosa and one year for C. radula and A. flabellata, then weekly over periods of 12 months for M. gloriosa and 6 months for C. radula. Reproduction of the three species occurs throughout the year with a maximal activity during the warm season. M. gloriosa and C. radula are capable of spawning several times a month. Fluctuations of reproductive intensity are related to temperature and salinity fluctuations.

A real-time polymerase chain reaction (PCR) assay was developed for the identification and quantification of two oyster species: Ostrea edulis and Crassostrea gigas. Two sets of primers and TaqMan-MGB probes were designed, based on partial sequences of the 16S rRNA gene. An amplification positive control system was also located in the 18S rRNA gene sequences. Closely related species of oysters and other bivalves, known to co-occur with the target species in European waters, were used to test the assay for cross-reactivity. The assay designed was specific for the target species and no signal or no significant signal was detected for all non-target species tested. The high sensitivity of this method was demonstrated since it is possible to detect just one larva (150–200 μm size) of each species even when it is present with others. Furthermore, this assay provided an acceptable quantification of the number of spiked larvae (1, 10 and 100 larvae) in plankton samples employing a standard curve for larvae.

Two methods for estimating bycatch-to-shrimp ratios were tested using Monte Carlo simulations. The Ratio Averager first calculates the ratio of bycatch to shrimp for each element of the sample and then averages all the entire sample. This method overestimated the ratio with a maximum bias as high as 4.5 times. In contrast, the Ratio Estimator or Ratio Estimation as termed in some literature first averages the sample catch rate of bycatch and shrimp and then calculates the ratio of the two averages. The Ratio Estimator performed quite well under all scenarios evaluated in this study, with a bias range from –1.7% to 2.8%. The reliability of the Ratio Estimator was also higher than the Ratio Averager, particularly when both bycatch and shrimp had high variability. Two sets of fishery survey data were used to demonstrate the difference in ratio estimates between the two methods.

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.

As in the female (Breton et al., 1988), plasma gonadotropin levels (GtH) in male roach were always the lowest the day of aggregation on the spawning areas, eventhough they were elevated 3 daysearlier. The levels increased during spawning and remained at a high level in most of the animalscaptured out of the visible spwaning areas, 3 weeks after the beginning of the spawning activity. During the same period the GnRH contents did not significantly vary in the hypothalamic lobes, the di-met-and myelencephalon. On the contrary there were marked variations in the pituitary gland and the telencephalon in which the GnRH levels were the highest the day of aggregation when GtH plasma levels were the lowest. In these two structures they decreased during spawning in correlation with the increase of the plasma GtH levels. These results are discussed in comparison with those obtained in the female and in relation with the possible endocrine and paracrine roles of the GnRH in these structures and mainly in the telencephalon.

Techniques were developed for labelling prey, and for gut content analysis in fish larvae. Labelling consisted of a short feeding period of the prey (rotifer and Artemia metanauplii) on black-drawing ink before supplying them to the larvae. Prey labelling was rapid and remained stable for at least 3 h when transferred into seawater. In addition, a method was tested to facilitate the observation of larval gut contents. The method, based on Dawson's technique, involved fixation, removal of lipids and clearance of turbot (Psetta maxima) larvae, which become transparent and ready for gut content analysis. This treatment did not interfere with the black ink label of the ingested prey.

The effect of dietary water content on Dicentrarchus labrax growthparameters and resistance to Vibrio anguillarum infection wasinvestigated using commercial pellets with identical energy contents and differentmoisture levels. The first experiment hypothesis was that moisturizing pelleted ration canhave an impact on Dicentrarchus labrax growth performance by theosmoregulation energy cost reduction. In a second time, the experiment explores the effectof water addition in pellets on the fish resistance to a disease. A specific device wasbuilt to uniformly moisturize dry pellets to different moisture levels, i.e. 8%, 20%, 40%and 60%. After an acclimation period and a 54-day rearing period, the control fish hadgrown from 72.7 ± 17.9 g to133.3 ± 29.4 g. Nosignificant differences were recorded for fish growth parameters. After the growth period,the tagged fish were mixed and challenged by bath exposure to live Vibrioanguillarum in triplicate. After 7 days, mortality was significantly lower inthe group of fish fed with pellets containing 60% water. Adding water toDicentrarchus labrax feed did not affect fish growth parameters butincrease its resistance to a Vibrio anguillarum infection. The moisturizing processcould be used to add specific compounds (such as probiotics or vitamins) to pellets justbefore fish feeding and could have a positive effect on fish rearing.

Bahía Magdalena, located on the southwest coast of Baja California Sur, Mexico (24°20'N, 111°30'W), is an important area for fishing of small pelagic fish. The Pacific sardine (Sardinops caeruleus) comprises more than 75 % of the total catch in the bay. Hydro-acoustic surveys were carried out in this bay using a single-beam echo sounder, Simrad EY-200 (200 kHz), during three oceanographic surveys (March, July and December 1996). Results demonstrate that in July more than 75 % of the positive observations (those echograms with more than 100 echoes in the volume sampled) and most of the echo counts were recorded in the 5–10-m-deep layer. During March and December, positive echograms in the upper stratum were below 50 % and most of the echo counts were detected in the lower layer (10–20 m). These results were related to the availability of Pacific sardine to the commercial fleet, specifically to the capture-per-unit-effort. Results support the hypothesis that sardines migrate during late summer and autumn and that a new recruitment occurs during the winter within the bay.

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.

Despite extensive knowledge of the genetic structure of sea bass (Dicentrarchus labrax) populations, no studies have investigated genetic structure within early life stages, or compared such structure between such stages and (sub)adults. Using nine newly developed microsatellite loci, we investigated patterns of genetic variation and relatedness among juveniles that settled in two NW Mediterranean nursery grounds in close geographical proximity. There was no evidence for differentiation among samples at settlement (θ = -0.0010), and no significant genetic relatedness. Nevertheless, significant departures from Hardy-Weinberg equilibrium were detected in each sample, which could not be attributed exclusively to the presence of null alleles and to Wahlund effect. These results are compared with and discussed in relation to the genetic structure of adults described in the same area 10 years ago.