Anti-Bacillus megaterium activity was measured in unfractionated plasma withdrawn from three common US East Coast bivalve molluscs: an oyster Crassostrea virginica and the mussels Geukensia demissa and Mytilus edulis. The activities of the plasma samples from these bivalves were also measured against a C. virginica pathogen Perkinsus marinus. Strong anti-B. megaterium activity was measured in plasma from C. virginica and M. edulis, but was not detected in G. demissa. Bactericidal activity was found in hemocyte extracts from all bivalves in this study, suggesting a cellular origin of cytotoxic humoral factors. Peptides (< 10 kDa) were separated from the plasma samples by ultrafiltration; weak antibacterial peptide activity was quantified in C. virginica peptides, but not in peptides from the mussels. In the case of P. marinus, plasma from M. edulis or G. demissa was boldly cidal as compared to plasma from C. virginica. This difference in activity probably reflects the low pathogenicity of this oyster parasite for the mussel species tested. In summary, the bactericidal activity of plasma proteins from these bivalves showed considerable interspecies variation and did not necessarily correlate directly with antiprotistan activity. When present, antibacterial and antiprotistan activities seemed to be associated with plasma proteins rather than < 10-kDa plasma peptides, with the possible exception of C. virginica anti-B. megaterium activity and the occasionally expressed anti-P. marinus activity of M. edulis peptides. The precise identity of the plasma protein(s) responsible for the antimicrobial activities measured have yet to be determined, but it is likely that agents other than, or in addition to, lysozyme play significant roles in the process.

The abundance of prey ingested by brown trout (Salmo trutta) were compared with the abundance of drifting invertebrates in a mountain stream managed by hydropeaking, upstream (site A) and downstream (site B) of a hydroelectric power plant. During power generation, flow and temperature were the two main environmental factors modified. The natural flow in the river below the outlet may be enhanced several times a day from 1 to 11 m3.s–1 in summer and winter, and from 5 to 15 m3.s–1 during spring spates. During hydropeaking, the water was cooled by an average of 6 °C in summer and warmed by an average of 2 °C in winter. Overall drift density was higher at site B than at site A. There was a clear diel pattern of drift at site A, with low drift density during the day and high drift density at night, whereas no clear diel pattern was observed at site B. Below the plant, at site B, drift pattern appeared to be influenced most by hydropeaking. The flushing action of peaking flows caused a catastrophic drift, which was highest in autumn when the difference between natural and peak flows was greatest. Juvenile trout were adversely affected by hydropeaking conditions and subsequently their density and biomass were reduced by 30% from site A to site B, whereas no significant difference was noticed for adults. Gut contents analysis showed that brown trout chiefly fed on the most available prey items at both sites. Fish did not seem to feed in response to diel drift patterns above the plant, whereas they chiefly used drift pulses generated by peaking flows below the outlet. Under natural conditions, fullness indices increased from autumn to summer, suggesting they may be related to prey availability and changes in water temperature. In the regulated section, fullness indices were the lowest in spring, i.e. the season when peak flows added to snowmelt floods, suggesting a prominent role of high current velocities through habitat suitability, position maintenance, and ability to capture preys. Although hydropeaking is known to disturb trout population dynamics in this and other rivers, this kind of river regulation (natural discharge except during periods of power generation, and intermittent hydropeaking from a separate reservoir) allowed the maintain of brown trout below the outlet, probably because the river returned to natural conditions when the plant was inoperative, and because daily artificial fluctuations in flow and temperature remained within the limits of natural seasonal variations.

The body components of female rainbow trout (Salmo gairdneri) reared in an experimental fish farm were studied during sexual maturation. For a period of 13 months, carcass, liver, gut and ovaries were sampled every month and their fat and non fat constituents analysed. In the trout, lipids are mainly stored in the carcass and to a less extent in the gut and ovaries. The distribution ranged from 68 to 73%, 31 to 6% and 0.1 to 20%, respectively from the beginning to the end of sexual maturation (March-November). Whatever the stage, carcass and visceral total lipids (TL) were mainly composed of neutral lipids (NL). The ovarian NL relative to TL content decreased from 90% during the first gonadal slow growth phase (SG. I from March to June) to 60% at ovulation in October or November while the proportion of phospholipids (PL) increased during the second slow growth phase (SG. II from July to August) and the rapid growth phase (RG from September until ovulation in October or November). This observation suggests that trout preferentially incorporate fatty acids into phospholipids in the oocyte during late ovarian growth.

During sexual maturation there was a large mobilisation of carcass and visceral lipid reserves, but non fat dry matter (NFDM) was only slightly changed. In our experimental fish (mean weight 1200 g) the loss of lipids averaged 76 g (42 and 34 g, respectively from the carcass and gut) versus 33 g for NFDM (from the carcass mainly). Loss of visceral lipids began during SG. I and ceased at ovulation in November, whereas loss of carcass lipids seemed to start during the RG phase and finished 1 month after ovulation.

Since the June 1995 ICES Symposium on Fisheries and Plankton Acoustics in Aberdeen (MacLennan and Holliday, 1996) the use of acoustics for studying zooplankton has seen important advances. Acoustical monitoring of small-scale zooplankton distributions can now be done at intervals of a fraction of a minute. Resolution at vertical spatial scales of tens of centimeters is now easily achieved with commercially available sensors. Multiple-frequency echo-ranging sensors (TAPS™) have been deployed in an up-looking mode on the bottom, and on moorings looking up, down and horizontally. Real-time telemetry provides data on plankton distributions at ranges up to tens of meters from the sensors for periods of weeks to months. These sensors allow one to estimate total zooplankton biomass and the size-abundance spectrum of the animals in the water column at different depths and times. When a profiling CTD and multi-spectral optical sensors were used to define the physical environment and phytoplankton distributions near an acoustical zooplankton profiler, bold relationships were observed between measured spatial and temporal patterns. New methods in zooplankton acoustics are illustrated with data collected from these sensors while monitoring thin, sub-meter thick layers of plankton and diel migrations of benthopelagic crustaceans.

Is the seasonal growth of Strangomera bentincki (Clupeidae) and Engraulis ringens (Engraulidae) a consequence of their reproductive strategy to adapt to the seasonal upwelling ecosystem they inhabit? This question is addressed by analysing monthly length-frequency data, gonadosomatic index and condition factor of the species in relation with the seasonal patterns of environmental variables. Modal progression analysis of mean length-at-age of cohorts along the time axis was used to study the growth in the period 1990–1997. A seasonally oscillating growth curve was estimated for both species, with the slowest growth rate occurring between April and May, a few months before the higher reproductive activity occurring in August–September. The reproductive strategy is to spawn when environmental conditions are related with onshore transport in winter (August), favouring the concentration and retention of eggs and larvae. One month later, a moderate upwelling determines an enrichment in food particles and the spawning area is transformed in a nursery area for juveniles. The reproductive strategy is combined with an ‘energy storage strategy’ during the period of upwelling. The energy stored is used for reproduction several months later, affecting the growth process of the species. It is concluded that the regularity in the seasonal growth in both species is a response, from an evolutionary point of view, of a long-term reproductive adaptation to the seasonal upwelling ecosystem of the central southern area off Chile.

This is an overview of the hormones which may be involved in food intake control in fish, and some hypothetical pathways of their action are given based on mammalian knowledge. Most of the observed effects of these hormones may result from four types of mechanisms, each hormone acting by one or several as follows: (1) hormones could have a direct effect on central nervous system centres, associated with food intake behaviour or via vagal afferent neurons; (2) an indirect effect may occur via the gut which slows gastrointestinal transit, thus resulting in stomach distention which activates vagal afferent neurons; (3) they could have an indirect effect, acting directly on intermediary metabolism via glucose, free fatty acids or amino acids mobilization or storage; (4) the last possible pathway is an indirect effect by modifying directly or indirectly secretions of other hormones involved in food intake control. Some of these hormones (CCK, PYY, glucagon, adrenalin) act as short-term factors which regulate meal ingestion and are generally inhibitory factors. On the other hand, other hormones (GH, TH, and leptin) require more time to modify foodintake behaviour, and appear as stored calorie regulators. However, the orientation of hormones to short-term or to long-term action is not always clear as it has been noted for insulin and glucocorticoids, and may depend on the hormonal and metabolite environment.

A longline ‘métier’ using small hooks for ‘red’ sea breams (Pagellus acarne and Pagellus erythrinus) in the Algarve (south of Portugal) was studied. Experimental longlining was carried out with three sizes of "Mustad" round bend, flatted, spade end Quality 2316 DT hooks (numbers 11, 13 and 15) and two types of bait: razor shell (Ensis siliqua) and mud shrimp (Upogebia pusilla). A total of 3 328 fish and at least 36 species were caught with 33 600 hooks fished in 28 longline sets. Five species of sea breams (Sparidae) accounted for 79% of the catch: Pagellus acarne, Pagellus erythrinus, Diplodus vulgaris, Spondyliosoma cantharus, and Boops boops. High catch rates of 20-30 fish per 100 hooks were made in a number of 1 200 hook longline sets, with total catch weights of 40 to more than 60 kg per set. In general, the smallest hook (number 15) had the highest catch rate. Bait type did not significantly affect the catch size distributions. Although more fish were caught with the razor shell bait, higher catch rates of ‘red’ sea breams were obtained with mud shrimp. Catch rates were also affected by the location of the fishing grounds and the time of the set, with the highest catch rates obtained when the longline was set within two hours before sunrise. A wide size range was caught for each species, with highly overlapped catch size frequency distributions for the three hook sizes used. Except for Spondyliosoma cantharus, few illegal-sized fish were caught, even with the smallest hook. The logistic model fitted by maximum likelihood was used to describe hook selectivity for Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, and Spondyliosoma cantharus.

A study on nitrogenous and phosphorous waste production in European seabass (Dicentrarchus labrax) was carried out in a flow-through land-based farm. The main objectives were (i) to calculate nitrogenous (N) and phosphorous (P) waste production (particulate and dissolved) from in situ measurements for different rearing ponds with specific fish biomasses, fish sizes and flow rates, (ii) to establish nitrogenous and phosphorous waste production budgets, ratios and equations, and (iii) to compare, for the whole farm, in situ measurements to estimate N and P waste production from waste equations. Waste production was manifest by an increase in concentrations of total ammonia nitrogen, total Kjeldhal nitrogen, particulate nitrogen, dissolved phosphorus and total phosphorus concentrations in the outlet water compared to the inlet water for both batches and whole farm. However, no production of nitrite or nitrate was observed. In our budgets, the N and P amounts from biomass gains and wastes were explained by the N and P derived from feed over the range 83.9−105.2 % and 66.5−104.6 % respectively, depending on the fish batch. Values were respectively 103.4 and 87.5 % for the same calculations in the farm. When the whole-farm waste production was calculated from previous equations derived from batches, and then compared with the measured data, the percentages of recovery (estimated by the ratio predicted data/measured data) were 88 and 94 % for total-N and total-P respectively.

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.

The exposure of freshly spawned, immotile carp sperm to hypoosmotic media triggers the initiation of calcium-dependent flagellar motility. Intracellular calcium concentration has been thought to be the critical component in motility initiation, possibly acting through a novel signalling pathway. The sensitivity of sperm cells to changes of osmolality of the environment raises the question whether a mechanoregulated osmosensitive calcium pathway is involved in the activation mechanism of carp sperm motility. The sperm cells are in a depolarized state in the seminal plasma (Ψ = –2.6 ± 3 mV) and they hyperpolarize upon hypoosmosis-induced activation of motility (Ψ = –29 ± 4 mV). The intracellular sodium [Na+]i, potassium [K+]i and calcium [Ca2+]i ion concentrations were determined in quiescent cells, and at 20, 60 and 300 s after activation. The [Na+]i and [K+]i of the quiescent cells were similar to the [Na+]e and [K+]e of the seminal plasma. Following hypoosmotic shock-induced motility, both [Na+]i and [K+]i decreased to one-fourth of the initial concentration. The [Ca2+]i doubled at initiation of the motility of the sperm cells and remained unchanged for 5 min. Bepridil (50–250 μM), a blocker of the Na+/Ca2+ exchanger, blocked carp sperm motility reversibly. Gadolinium, a blocker of stretch-activated channels (10–20 μM), inhibited sperm motility in a dose-dependent manner and its effect was reversible. Hypoosmotic shock fluidized the membrane and gadolinium treatment made it more rigid in both quiescent cells and hypotonic shock treated but immotile sperm cells. Based on these observations, it is suggested that, besides the well-known function of potassium and calcium channels, stretch-induced conformational changes of membrane proteins are also involved in the sperm activation mechanism of common carp.

Egg quality is one of the most important factors determining larval viability. The study of oocytes released by ‘wild' broodstock will contribute to the definition of quality criteria applied to hatcheries as well as being an indicator of the oyster reproduction potential and aquaculture ongrowing systems. The aim of this study was to determine the relationship between condition of Crassostrea gigas spp. angulata (Portuguese strain) from ‘wild' broodstock (condition index, gonadal maturity and number of oocyte released), oocyte biochemistry and hatching rate of eggs during the spring/summer of 1995. Stages of gonadal maturity and condition index indicated that natural spawning of this species occurred between April and August with the highest spawning intensity occurring in June. Analyses demonstrated that C. gigas oocyte organic matter consist of 44–74 % proteins, 16–38 % lipids and 7–12 % carbohydrates. A significant relationship was observed between some biochemical parameters – organic matter and lipid content – and broodstock condition index and hatching rate. It seems that these two oocyte parameters (organic matter and total lipids) could be used to define quality of oocyte and thus larval viability. The oocyte protein content was also found to be associated with broodstock and larval quality. In summary, these data are a contribution to the knowledge of the reproductive cycle of oysters in Europe and may be useful in improving hatchery management of this species.

French oyster farming has been subject to severe mortalities during the summer months.Results from the research program “Morest”, which ran from 2000 to 2006 and examined thepossible causes of these mortalities, led to the construction of a model to explain theinteraction between environmental factors, oyster physiology and different opportunisticpathogens underlying oyster summer mortality. Temperature, food, reproduction and stresswere the main factors required for oyster mortality. Genetically-based resistance (“R”oysters) or susceptibility (“S” oysters) to summer mortality was revealed by divergentselection. Building on these results, a literature search was made in 2007 on themolecular origin of genetic resistance to such a complex mortality risk. The objectiveswere to lay a foundation for the preparation and orientation of future research directionsand to improve understanding of the underlying physiological mechanism leading to summermortality. Three years later, the resulting conceptual analysis reported here waspresented as an introductory lecture to Physiomar 2010, a conference where many newresults contributing to this research field were also reported. The literature reviewhighlighted two major review articles: the first dealing with nutrition and reproduction(Schneider 2004), the second with reproduction,temperature, oxidative stress and mortality (Heineinger 2002). The effect of nutrition level on energy orientation to growth orreproduction is controlled by endocrine factors. Among these, neuropeptide Y (NPY),ghrelin and leptin neuropeptides appeared to be potential candidates involved in germ-somaorientation in relation to trophic conditions. Depending on reproductive effort andtemperature, a metabolic stress resulting from the germ-soma conflict can appear,characterized by mitochondrial reactive oxygen species (ROS) production. Such an excess ofROS induces perturbations in mitochondrial activity leading to cell death. Many organisms,such as annual plants or the Pacific salmon, do not survive their first reproduction. Incontrast, others increase stress resistance by selection of antioxidant processes(superoxide dismutase SOD, catalase, etc.) through evolution, and survive firstreproduction. A similar difference was observed in the comparison made between R and Soysters, which differed in ROS production, SOD and catalase levels. Such factorscontrolling reproduction and ROS detoxification processes could therefore provide newmarkers for selection of oysters with better resistance to non-specific pathogens,complementing other classic selection approaches against specific pathogens or forimproved immunity. This antioxidant defence mechanism is found in many organisms includingvertebrates and in some invertebrates, including oysters. Its role needs to be consideredin pathology events involving other aquaculture species and it may also contribute toexplaining the increase in marine pathologies under anthropogenic environmental changes.

The black-browed (Thalassarche melanophrys) and Atlantic yellow-nosed (Thalassarche chlororhynchos) albatrosses and the white-chinned petrel (Procellaria aequinoctialis) are the seabird species most frequently captured by pelagic longline fisheries in the southwest Atlantic. This study estimates this type of bycatch and describes the spatial-temporal patterns of the incidental capture of these species by the Uruguayan pelagic longline fleet, based on data collected by scientific observers on 47 fishing trips from 2004 to 2007. Three generalized linear models (GLM) models were employed to predict bycatch for each species based on the observed data. We also developed a spatio-temporal species-specific analysis. Captures were recorded in Uruguayan waters, mainly over the slope and depth waters, and in international waters adjacent to Uruguay, the north of Argentina, and the south of Brazil. The highest catch rates for black-browed albatrosses and white-chinned petrels were recorded on the Uruguayan slope from fall to spring, while the highest values for Atlantic yellow-nosed albatrosses were recorded further to the north, in the international waters off Brazil in late winter. The average estimated number of black-browed and Atlantic yellow-nosed albatrosses and white-chinned petrels caught during the study period was 1683, 257 and 239 birds, respectively. Taking into account the total effort of the fleet, these values represent an estimated catch rate of 0.276, 0.042, and 0.039 birds/1000 hooks for these species, respectively. The results of the present study suggest that the annual impact of this fishery is medium to high on the black-browed albatross, low on the Atlantic yellow-nosed albatross and low on the white-chinned petrel. However, the situation of these species in the southwest Atlantic should be viewed with considerable concern, as our understanding of the impact of the bycatch on their populations requires more research. Any effort to reduce seabird mortality in the southern hemisphere should target this geographic region.

Swimming capabilities and in situ measurement of muscle activity from adult Atlantic salmon (Salmo salar) at two seasonal temperatures were measured using radio transmitted electromyogram (EMG) signals. Forced sustained levels of activity and critical swimming speeds were determined and correlated to radio transmitted EMG signals using a modified Blazka swim speed chamber. There were no differences in swimming performance levels between tagged and untagged individuals. At 18 °C, sustained activity and critical swimming speeds were approximately 70% and 20% higher than at 12 °C, respectively. No differences in burst activity were observed at these temperatures. EMGs recorded from salmon during ascent of an artificial flume at cold temperatures revealed that overall muscle activity is greater than that observed for critical swimming speeds. This implies that white muscle may be recruited at this temperature. However, in contrast, most activity at 18 °C is below that observed during critical swimming speed. Moreover, salmon required almost twice as long to traverse the flume at 18 °C than at 12 °C. Together, our data demonstrates that salmon may recruit white muscle fibres and incur an oxygen debt at colder temperature as a strategy for ascending velocity obstructions at a quicker rate.

In the Western and Central Pacific Ocean (WCPO), which accounts for over half of world tuna production, purse seine effort and catch on floating objects have increased significantly due to a rapid increase in the use of fixed and free-floating fish aggregation devices (FADs). FAD fishing has had an impact on the current status of the stocks of the three main target tunas in the equatorial WCPO, skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares) and bigeye (T. obesus). FADs have been shown to influence the behaviour and movement patterns of the three tuna species with the juveniles of each species occupying shallower habitats when associated with FADs. Aggregation of tunas around drifting objects increases their vulnerability to purse seine gear, particularly for juvenile and small size classes. Further to the impacts on the target stocks, the use of FADs has increased the vulnerability of other fishes to the purse seine method, including some shark and billfish species. Given the concern over FAD-related fishing effort on target and bycatch species, there is a need to understand how FAD use affects target and bycatch stocks. Science needs to better support management decisions are highlighted including the need to identify the magnitude of broader community-level affects.

Between 1994 and 1999, several sampling designs were used to measure the growth of the black-lip pearl oyster, Pinctada margaritifera var. cumingi at different sites in French Polynesia. Using a common statistical method, growth data were analysed for nine sites and showed significant geographic variability. Parameters of the Von Bertalanffy model, fitted on the nine data sets, ranged from 147 to 186.5 mm for the H∞ parameter and from 0.42 to 0.58 year–1 for the k parameter. The φ parameter (combination of H∞ and k) provided a ranking classification of growth in these nine sites: growth was low in closed atoll lagoons, such as Takapoto, whereas the island lagoons and ocean habitat supported a very promising shell growth. Calculated on the basis of these models, two parameters of interest for pearl farming were computed: 1) the time for pearl oysters to reach a size of 100 mm (size at which they are suitable for nucleus implantation), which ranged from 21 to 26 months, and 2) the annual shell growth increment at this size (correlated to the rate of nacreous deposition on the pearl), which varied from 19.7 to 31.8 mm·year–1. The combination of these two sets of results demonstrated that the time necessary to produce a comparable pearl varied significantly according to the site. Several hypotheses to explain the differences observed in the growth of P. margaritifera in these nine sites are proposed. The most reasonable would appear to be: 1) the negative effect of high temperature (> 30°C), and 2) the degree of water renewal and food supply around the bivalve. Although this paper demonstrated significant variability in growth performance in the nine investigated sites, further investigations are needed, especially concerning the flesh growth rate. Indeed, this highly relevant parameter, which reflects both bivalve health and the suitability of farming sites, has received very little attention to date.

Ecological risk assessment is a useful methodology for assisting the management of fisheries from an ecosystem perspective. Atlantic tuna fisheries, managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), are economically important and interact with several bycatch species. In spite of these interactions, no comprehensive ecological risk assessment has been conducted for bycatch species caught in ICCAT fisheries. In this paper, we followed a two stage approach with the objective of assessing the relative risk of species being negatively impacted by Atlantic tuna fisheries. An analysis of the ICCAT bycatch species list (which includes all species reported to have interacted with different tuna fishing gears operating in the Atlantic) revealed that most of these species are caught in longline fisheries, followed by gillnets and purse seines. According to the IUCN red list, 7 species of the ICCAT bycatch list (3 coastal sharks, 3 sea turtles and one seabird) are categorized as critically endangered. In our study, and based on their life history characteristics, marine mammals and coastal sharks caught in ICCAT fisheries showed the highest intrinsic vulnerability values. A productivity susceptibility analysis for the European Union (EU) tropical tuna purse seine fleet and the United States (US) pelagic longline fleet revealed two groups with high relative risk scores. The first one included pelagic and coastal sharks, characterized by relatively low productivities, and the second one included teleosts, characterized by higher productivities but high susceptibility to purse seine and longline gears. Some alternative approaches to conduct productivity susceptibility analyses in the context of ecological risk assessments are discussed.

Le banc ostréicole de Ronce (175 ha) au sud du bassin deMarennes-Oléron (France) constitue un site atelier expérimental pourl'étude des mortalités estivales de l'huître creuse Crassostreagigas. En 1997, la croissance, la maturité sexuelle, la survie etl'environnement des élevages à plat et sur tables sont comparés surquinze sites expérimentaux. En 7 mois, le taux de mortalité desélevages à plat atteint 23−33 % contre 8−19 % pour les élevages surtables. La mortalité varie avec la saison. Elle s'intensifie avec latempérature, en période de pré-ponte et de catabolisme duglycogène. Des modèles statistiques de production de chair sèche del'huître sont établis selon la latitude de la longitude des sites. Cesmodèles (en poids sec) sont orientés nord - nord-ouest et montrent que ladisponibilité alimentaire pour les cheptels d'huîtres, diminueprogressivement du large vers le fond de la baie. Les rendements biologiques (poidstotal), sont compris entre 85 et 2 %, respectivement pour des sites sur tables à25 et 50 % d'exondation. Pour les élevages à plat, une perte de productionsupérieure à 10 % est enregistrée dans certains parcs du sud dubassin. Les meilleurs sites, à 50 % de production (poids total), sontsitués dans la partie est - nord-est du banc de Ronce.

The survival of turbot eggs and the rearing capacities of larvae stemmed from artificial fertilization practices using frozen-thawed spermatozoa were evaluated. Furthermore, the viability of sperm samples stored during a 9 month period in liquid nitrogen was assessed. No significant difference in the fertilization rate, hatching rate, survival and wet weight of 10-day old larvae were observed using fresh or frozen-thawed spermatozoa. The motility recorded at 10 s and 60 s post-activation and the fertilization capacity of frozen-thawed spermatozoa were not significantly decreased during a 9 month storage period in liquid nitrogen. These results confirm the high quality of the turbot spermatozoa stemmed from the cryopreservation process, allowing their use for routine aquaculture practices.

The development of techniques for production of gynogenetic, androgenetic, polyploid, and monosex progenies in common carp (Cyprinus carpio L.) is described from a chronological perspective. Gynogenetic progenies were obtained either by suppression of the second meiotic division in eggs (meiotic gynogenesis) or by suppression of the first mitotic division in haploid embryos (mitotic gynogenesis). As a rule, gynogenetic progenies of common carp were all-female, revealing female homogamety (females—XX, males—XY) in this species. Induced gynogenesis results in increased homozygosity; the rate of increase depends on the type of gynogenesis. Inbreeding coefficient (F) for one generation of meiotic gynogenesis in common carp is about 0.6, while diploids obtained by mitotic gynogenesis are homozygous for all genes (F = 1.0). Mitotic gynogenesis was used for production of clones in common carp. In androgenetic progenies of common carp, YY males were identified, that after crossing with normal females (XX) produced all-male progenies. Triploids of common carp are characterized by a significant reduction in gonad development (especially ovaries). However, the reduction in gonad development did not result in an increase of somatic growth rate of fish. The procedure for androgen treatment to induce phenotypic sex reversal in genotypic females (XX) was elaborated. All-female progenies of common carp were produced on a large scale by crossing normal females (XX) with hormonally sex-reversed males (XX). Rearing of all-female progenies in conditions when fish normally reach sexual maturity before reaching of market size increased production yield by 7–8%. In a few cases distant hybridization resulted in polyploidy of fish without application of any physical treatment. The ability of hybrid females between crucian carp (Carassius auratus) and common carp to produce diploid (with unreduced chromosome number) gametes resulted in opportunities to produce triploid and tetraploid hybrid progenies.