From April 1995 to April 1996, the annual reproductive cycle of the Eurasian perch Perca fluviatilis was studied at the Fishfarming Lindre Center (Moselle, France). At monthly intervals (at intervals of 10 days during the periovulatory period), 5 females were caught and dissected. From sampled organs, the gonado-, hepato- and viscerosomatic indexes (GSI, HSI, VSI) were calculated, oocyte diameters (OD) and the plasma levels of testosterone (T), 17β-estradiol (E2), 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and protein-phosphorus (PPP) were measured. After the sexual resting period observed from May to August (GSI < 1 %, OD < 200 μm, VSI = 4-6 %), oogenesis began in September when the water temperature decreased from 26.4 to 14.1 °C. The GSI increased progressively until mid March (15 %), then rapidly until spawning (25 %, OD = 850 μm) which occurred in April (14-15 °C). The plasma levels of T, E2, 17,20β-P and PPP were low during the sexual resting period. E2 and PPP levels increased significantly at the onset of the oogenesis in September, then the E2 level raised abruptly in November (3-4 ng · mL−1). In December, the T level increased rapidly to 15-20 ng · mL−1. The testosterone, E2 and PPP levels remained very high until spawning, indicating the existence of active vitellogenesis. The highest HSI (2.1-2.2 %) recorded in winter confirmed this. During the periovulatory period, a peak of E2 (4 ng · mL−1) appeared, whereas T level diminished. In this study, 17,20β-P levels remained low (0.2-0.6 ng · mL−1) and relatively constant. No 17,20β-P peak was observed during the periovulatory period. Sampling at 10 day intervals was probably inadequate to specify the hormonal variations related to the final oocyte maturation and the ovulation.

Dry diets containing varying levels of dried fermented fish silage and soybean meal blend (FS: SBM) as replacement for 25,50 or 75% of fish meal protein were fed to juvenile Oreochromis niloticus (8.2 ± 0.1 g) and Clarias gariepinus (10.8 ± 0.3 g) at 5% body weight per day for 70 days. Diets containing co-dried FS: SBM supported weight gains and growth rates similar to those in the control treatment without significant differences (p > 0.05). Feed conversion, protein efficiency ratio and protein productive values followed a similar trend with growth performance values. Apparent protein digestibility decreased in both fish species with increasing dietary level of co-dried FS: SBM Carcass composition of experimental fish were not affected by the diets and morphological defects were not observed. Results indicate that co-dried FS: SBM can partially replace fish meal protein as well as establish the potential of utilizing waste/undersized tilapias as a protein feedstuff in dry aquaculture diets.

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.

With the aim of improving dry diets for first feeding of Heterobranchus longifilis larvae, the effect of dietary lipid sources on growth rate, survival rate and fatty acid composition of fry from 2 days up to 17 days of age was evaluated. Six feeding regimes were tested: Artemia nauplii which served as a reference, and 5 experimental dry diets differing only by the lipid source. The different oils used for the different experimental diets were the following: cod liver oil, palm oil, copra oil, peanut oil and cotton seed oil. Each diet was tested on duplicate groups of 400 larvae placed in the 40 l tanks of a recirculating system (27-29 °C) and fed to excess six times per day every 4 hours. Separation and identification of the fatty acids of diets, eggs and fry were carried out by gas-liquid chromatography. After 15 days of feeding, survival rates were high for all treatments (71-87%) and did not differ significantly. By contrast, growth rates were largely influenced by the feeding regime. Fry fed with Artemia were significantly bigger (289 mg) than those fed artificial dry diets (79-115 mg). However, it was found that the specific growth rate of fry fed Artemia was superior to that of fry receiving dry diets only for fish of less than 50 mg body weight, indicating that Artemia presents a nutritional advantage only for fry at their youngest stages of development (first 6 days of feeding). Among the artificial dry diets, the best results were obtained with diets containing palm or copra oil, the lowest growth rate being observed with the cod liver oil diet. Peanut and cotton seed oil diets led to intermediate results. The fatty acid composition of the whole fry reflected that of the experimental diets. All together, the results indicated the existence of an optimal ratio between n-3 and n-6 fatty acids for covering essential fatty acids requirement of the fry. Growth rates tended to be reduced by an excess of n-3 fatty acids (cod liver oil) or by an excess in n-6 fatty acids (cotton seed oil) as well. Evidence of the occurrence of HUFA (20:4n-6 and 22:6n-3) biosynthesis are given.

Among the gastropods, some muricid shells are composed of an inner aragonitic crossed lamellar layer and a calcitic prismatic outer layer. The analysis of the structure and composition of the two layers of Concholepas shows that the crossed lamellar layer is similar to those of other Mollusc taxa. Sr, Mg and S contents are low in both layers. According to infrared spectrometry, the organic content of the outer calcitic layer is higher than that of the aragonitic crossed lamellar layer. The study of the nanostructure allows for the proposal of a new 3D interpretation of the fine structure of the crossed lamellar layer. The calcitic prismatic layer is compared with the outer calcitic prismatic layer of an archaeogastropod genus: Haliotis.

Un modèle écophysiologique déterministe de la croissance, de la reproduction et des interactions entre le bivalve et son environnement estuarien a été élaboré pour l'huître japonaise Crassostrea gigas. Pour fonctionner, le modèle a besoin de la température de l'eau, des concentrations en matière en suspension, matière organique particulaire, matière minérale particulaire, chlorophylle-a, phéopigments, protéines, lipides et glucides particulaires. Les fonctions de filtration, consommation, ingestion, absorption et respiration ainsi que les efficacités de rétention, sélection et absorption sont modélisées à l'aide de variables endogènes (poids sec de l'animal, allocation d'énergie entre la croissance et la reproduction) et exogènes (température, quantité et qualité de la nourriture). Le modèle simule l'évolution temporelle de deux compartiments : somatique et réserves-gonades. L'énergie provenant de la nourriture absorbée est allouée au compartiment somatique jusqu'à un maximum de croissance somatique. Ce maximum décroît avec l'âge du bivalve et ne dépasse jamais 0,02 g.j−1.individu−1. L'énergie en excès est alors attribuée au compartiment réserves-gonades. Cette représentation permet d'identifier les périodes de stockage de réserves et de gamétogénèse ainsi qu'une bonne simulation de l'intensité des pontes.Le modèle tient compte d'une efficacité de sélection plus importante pour les microphytes que pour les particules détritiques. L'efficacité d'absorption a été représentée en fonction du pourcentage de matière organique dans la fraction ingérée afin de tenir compte de la dilution de la nourriture par les particules minérales. L'efficacité d'absorption des microalgues varie de 20 à 60 %, tandis que pour les particules organiques détritiques, le modèle simule des valeurs négatives pour tenir compte des pertes fécales métaboliques. Ces formulations permettent de suivre l'évolution temporelle des quantités de microphytes et de matières détritiques rejetées sous la forme de pseudofèces et de fèces.

As a first step in assessing the viability of periphyton-based fish production in South Asian pond aquaculture systems, the effects of artificial substrates on development of periphyton and on water quality were evaluated. Earthen ponds (10 × 7.5 m) were provided with an artificial substrate constructed from poles of either bamboo, kanchi or hizol tree branches (1.0 m2 artificial substrate per m2 pond surface). Higher periphyton biomass, in terms of dry matter (DM) (4.9 mg cm–2) and chlorophyll a (11.5 μg cm–2) developed on hizol and bamboo, respectively. Periphyton ash content was higher on hizol (41%) than on the other two substrate types (29%). Protein content of the periphyton growing on bamboo (38% of ash-free dry matter (AFDM)) was 50% higher than that on the other two substrate types. Maximum periphyton productivities of 1.01, 1.38 and 1.03 g C m–2 d–1 were obtained for bamboo, hizol and kanchi substrates, respectively. Taxonomic composition of periphyton showed a rapid development of a relatively stable community with few differences between the substrate types. In total, 56 genera of algal periphyton and 35 genera of phytoplankton were identified. Based on a periphyton productivity estimate of 2.2–2.8 g AFDM m–2 d–1, periphyton alone can sustain an estimated fish production of 5000 kg ha–1 year–1 through the addition of a substrate area equivalent to 100% of the pond surface area.

The proliferation of the voluntarily-introduced cupped oyster, Crassostrea gigas, has attained the proportions of species invasion in many intertidal habitats in Europe, presumably resulting from successful reproduction of farmed individuals. It is thus imperative to better understand the reproductive characteristics of farmed oysters, since they are directly under human control. We quantified the dry tissue mass (DTM), gametosomatic index (GSI), and reproductive cycle of farmed oysters at two sites in Bourgneuf Bay, France, in relation to environmental parameters using continuously-recording probes in 2005 and 2006. The GSI was developed for this study, based on the actual area occupied by gametes, rather than the area of the gonad previously used for quantitative histological estimation of reproductive effort. The two sites, intermediate – (IT) and high-turbidity (HT), differed markedly in the amount and quality of particulate suspended matter, and also in fine-scale temperature variations. Oysters at both sites presented two spawning periods in both 2005 and 2006; Bourgneuf Bay is thus near the northernmost European limit for a 2-spawning cycle in Crassostrea gigas. Gonad maturation was initiated when spring water temperature reached 8–10 °C, and gamete atresia occurred when water temperatures transiently dipped to 15–18 °C. Spawns, which occurred above 18 °C, were timed by fine-scale water temperature variations. Particulate organic matter quality peaks, coinciding with gonad maturation, were related to DTM variations before spawning periods, for the IT oysters in both years, and for the HT oysters in 2006. The reproductive effort (GSI) of oysters was similar at both sites; however, the fates of the gametes differed according to site. At the first spawning, the IT oyster gamete emissions were +1 month delayed, as were peak water temperatures greater than 18 °C, and more pronounced, compared to the HT site. Although the second spawning showed high proportions of atretic oocytes at both sites in both years, the IT oysters evacuated twice as many gametes as the HT oysters in 2005. The IT conditions therefore appear more suited to Crassostrea gigas gamete evacuation than the HT conditions.

The edge and isthmus of the mantle of Pinctada margaritifera (Mollusc, Bivalvia) were studied using light and electron microscopy from a morphological and histochemical point of view. Six areas with several subareas were differentiated in the mantle edge. One of these areas is similar to the epithelium isthmus. Trials to elucidate the nature of the pigment responsible for the black colour of the shell and pearl indicate a melanin-like material. Possible functions of the distinctive epithelial areas in Pinctada margaritifera mantle are discussed according to available data on the secretion of organic matrix of the shell, protein selerotization and deposition of crystals in some pearl-forming molluscs. Three different epithelial areas in the outer mantle edge of Pinctada margaritifera are probably involved in the sequential processes of deposition of calcite prisms, aragonite fibres and aragonite rhombs.

Adult two-year-old broodstock sea bass (Dicentrarchus labrax), raised in captivity, were fed ad libitum a natural diet (trash fish) until the end of their first spawning, and maintained under natural conditions of light and temperature. Six months before the second spawning, fish were randomly separated in two tanks with running sea water (salinity 37.80‰, pH 8.3) and maintained under similar environmental conditions. Fish were fed two different ration levels: group F, 1.04%, and group H, 0.45% body weight/day. The Jow ration supplied affected broodstock growth as indicated by decreased growth rates in weight and condition factor in group H, when compared to group F. The mean fecundity per female (No. eggs/female) in group H fish was similar to that from F group, while the relative fecundity (No. eggs/kg female) was more elevated in the H group. However, group H showed a delay in spawning time and slightly higher number of spawnings per female and larger spawning period, when compared to group F fish. In addition, group H females had reduced 17β-estradiol (E2) plasma levels and presented vitellogenic oocytes in the ovary a month later than group F females. By contrast, the vitellogenin (VGT) plasma levels remained similar between groups over the reproductive cycle. The egg quality (i.e. percentage of buoyant eggs), the egg biochemical composition and larval survival at hatching were similar between the two groups. The larvae from both groups also exhibited the same survival after 40 days of culture, although group H produced smaller eggs that yielded smaller newly-hatched larvae. Although the low ration supplied significantly reduced the growth and E2 plasma levels of sea bass, these preliminary results suggest that these changes do not dramatically affect the egg viability or the survival of larvae 46 days after hatching.

The tanker “Sea Empress” grounded at the entrance to Milford Haven in February 1996, releasing 72 000 t of Forties blend crude oil and 480 t of heavy fuel oil into the waters of southwest Wales. An estimated 15 000 t of emulsified oil came ashore along 200 km of coastline. A fishery exclusion zone was established to protect consumers of fish and shellfish, and monitoring was instigated in order to establish the degree and spread of contamination. A wide range of further studies were conducted with the aim of assessing the overall impact of the spill. In this paper we report on the establishment and subsequent lifting of fishing restrictions and the results of the fish and shellfish monitoring programme. The application of a range of biological effects techniques which illustrated sublethal impacts is also described. In retrospect, the impact of the spill was much less than would have been expected from the quantity of oil spilled. This was due to the circumstances of the spill, which led to fresh crude oil, amenable to chemical dispersion, being released during each ebb tide and carried into deep water to the south of Milford Haven. This enabled the extensive dispersant spraying operation, which included the aerial application of 446 tof chemical oil dispersant in order to enhance the rate of natural dispersion of the oil. This reduced the impact of the spill by preventing an additional 57 000 to 110 000 t of emulsified oil from impacting the beaches.

Surgery procedures were used to implant telemetry transmitters into the body cavity of adult (574–1 033 g) tilapias Oreochromis aureus in aquaculture tanks (4 m2, 1.5 m3, 26.5 ± 0.5 °C, ≥ 5.0 mg O2 l−1) and their effect on fish survival, growth and behaviour was evaluated. Only one out of 35 implanted fish died. With one exception, all fish consistently retained their transmitter until the end of the study (up to 30 months). Healing was faster when the incision was sutured with polyamide monofilament (5–14 days) than with other suture materials, due to tunnelling with atraumatic needles for catgut or fouling of braided silk. In all 10 fish sacrificed after 30 and 50 days, the transmitter had become encapsulated by connective tissue. No infection or damage to the viscera was observed.

The activity of four tilapias (903–1 033 g) equipped with motion sensitive transmitters was telemetered during the recovery from anaesthesia and surgical procedures. All four fish maintained a normal diurnal activity rhythm pattern throughout the study but had low levels of activity during the first 12–24 h. Based on the evolution of their resting posture after surgery, it is suggested that tilapias need 3 to 4 days to completely compensate the negative buoyancy resulting from anaesthesia and tagging.

This article aims to review 1) the major and most frequent human-induced physical disturbances and their consequences on coral reef habitats using a multi-scale approach, and 2) the scale-related indicators and conceptual aspects used to detect and measure the effects of these physical impacts. By physical disturbances, we mean direct perturbations that lead to the destruction/erosion of the carbonate framework. Human-induced direct physical disturbances are numerous from coastal development, tourism, harvesting, accidents and nuclear/weapon testing. Since methods for monitoring and measuring indicators are generally scale-implicit, coral reefs are first presented according to different ecological-spatial scales of organization, from colony to region (colony, reefscape, reef zone, whole reef, island and region). In this way, it is easier to link a couple {habitat, disturbance} to their potential indicators and to the descriptors they target. Three classes of descriptors, related to the response of the living component of coral reef ecosystem, are considered here: stony coral, reef fishes and the human uses. A synthesis of the different options for coral habitat assessments is proposed. We sort them according to their objectives (monitor, initial status or improvement of knowledge), their specificities (identification or not of a specific disturbances) and their scale of investigation (small, meso- or large scales). Usually, the majority of the indicators of human-induced disturbances are non-specific. They reveal that something is happening but not the actual causality and can only detect differences across time or space. A major weakness lies in the difficulty in deconvoluting the signals from a conjunction of stressors occurring at different scales. As such, a hierarchical concept of disturbances in coral reefs would be the next logical step to enhance our capabilities in monitoring and forecasting coral reefs status.

The distinction of the two cupped oysters Crassostrea gigas (Thunberg, 1793) and Crassostrea angulata (Lamark, 1819) into two species was chiefly due to their differing geographical distributions, C. gigas being present in Asia and C. angulata in Europe. Today it is commonly accepted that C. angulata and C. gigas are a single species according to morphological, genetic and F1 hybridization data. However, the demonstration of the fertility of their hybrids and the absence of any reproductive isolation remained to be investigated. Consequently, we studied the fertility of hybrids and sperm competition by performing three different experiments and producing G1 and G2 hybrid progenies between wild populations of C. angulata and C. gigas. Progenies showed very close developmental yields, at 24 hours after fertilization, according to dam taxa suggesting a bold maternal transmission of oocyte quality, but no reproductive isolation was observed between the two taxa. Significant decreases of developmental yields were noticed in C. angulata females with sperm competition, most probably due to early larval mortality. The fertility of hybrids C. angulata × C. gigas was demonstrated, which is further evidence that they are the same species. To definitively state the precise taxonomic classification of C. angulata and C. gigas, further studies are needed to (i) identify geographical zones where these taxa are in contact and (ii) assess their level of hybridization in these zones.

The presence of protease inhibitors in different ingredients used in fish feeds may negatively affect their digestive utilisation. The effect of inhibitors present in several protein sources on the activity of digestive proteases of sea bream was assessed using ‘in vitro’ assays. Inhibition produced by extracts of plant proteins ranged from 25 to 50% of total activity, whereas that obtained using animal protein sources ranged from 1 to 20 %. The exception was ovoalbumin, which showed the highest measured value (62 %). A plot of the inhibition values obtained by changing the relative concentrations enzyme/inhibitor resulted in different curves for different protein sources. The use of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) zymograms allowed visualisation of the aforementioned differences in inhibition. The importance of measuring protease inhibition in the preliminary evaluation of fish feed ingredients is discussed.

In populations of herring (Clupea harengus) or sprat (Sprattus sprattus), one typically observes a pattern of schools forming at dawn and dispersing at dusk, usually combined with vertical migration. This behaviour influences interactions with other species; hence a better understanding of the processes could contribute to deeper insight into ecosystem dynamics. This paper reports field measurements of the dispersal at dusk and examines two hypotheses through statistical modelling: that the vertical migration and the dissolution of schools is determined by decrease in light intensity, and that the dissolution of schools can be modelled by diffusion, i.e. active repulsion is not required. The field measurements were obtained during 3 days in March at one location in the Baltic Sea and included continuous hydroacoustical monitoring, trawl samples, and hydrographical CTD data. Echogram patterns were analysed using the school detection module in Echoview® and local light intensities were calculated using a model for surface illuminance. The data and the analysis support that schools migrate upwards during dusk, possibly trying to remain aggregated by keeping the local light intensities above a critical threshold, that schools initiate their dissolution when ambient light intensity drops below this critical threshold, and that fish subsequently swim in an uncorrelated random walk pattern.

The level of genetic differentiation between anadromous and non-andromous trout (Salmo trutta L.) coexisting in a Norman river (Oir river) was examined at 15 microsatellites markers. Despite a large amount of variation, no genetic differentiation was found between forms. Four domesticated stocks were also genotyped with the same loci. Highly significant differences were found with natural samples allowing to exclude a recent stocking effect on the Oir population. We conclude that the resident and anadromous trout form a single naturally reproducing unit in this river system. However, this conclusion could reflect particular ecological or demographic conditions in the Oir basin and needs to be validated in other hydrographical and ecological contexts.

The European catfish Silurus glanis has been cultivated in extensive ponds in central and Eastern Europe in association with carps for more than 100 years. The total production of S. glanis in aquaculture from ten European countries (Austria, Bulgaria, Croatia, Germany, France, Hungary, Greece, Macedonia, Poland, Czech Republic and Romania) was 602 t in 1993 and presently is about 2000 t. Production is increasingly from intensive pond culture or in heated/geothermal waters. The flesh is white, boneless, easy to prepare, and low in fat (6 to 8%). The taste is mild but is subject to off-flavour. The fish are filleted (yields about 40% without skin) and the flesh is cut into steaks or smoked). During the last 10 years, research in Czech Republic, France and other European countries have developed technologies for artificial reproduction, evaluated population genetics and addressed problems of conservation. Growth is higher in males and research is in progress to produce triploids fish. While propagation techniques have progressed, production remains low and the cost of production is still high. Thus availability is low and the product remains poorly known.

Shell malformations and histological effects of environmental concentrations of TBTF (2, 13.1 and 64.8 ng/l) were assessed on adult oysters Crassostrea gigas during a 1-month experiment, including both an exposure and a depuration phase. The results showed that the digestive gland is the primary target organ. Recoverable modifications were observed at the lowest concentration. Limited necrosis was observed at the highest concentration and a longer exposure could have led to extensive and irreversible tissue lesions. Shell malformations (chambering) were observed during the depuration phase. Finally the authors suggest that safe TBT levels in mariculture waters should be lower than 2 ng/1.

This paper describes both an experimental and a commercial-scale system for sludge dewatering and stabilisation. In the experimental system, back-wash water from rotating disk microsieves was settled in a conical sedimentation tank. This tank functioned well, commonly removing more than 75−80 % of the solids, at an overflow rate of 1.0−2.7 m·h−1. The hydraulic load was maintained low, so treatment efficiency was significantly positively influenced by inlet concentration and not inflow rate. Lime was added to the settled sludge. More than 99.9 % of the pathogenic viruses and bacteria studied were killed within 7 days at pH 12. In the commercial system, a newly developed combined effluent treatment and sludge processing system, was located in a large Norwegian salmon (Salmo salar) smolt farm. Four drum microsieves were used to separate particles from the primary effluent flow. The back-wash water, amounting to a maximum of 0.3 % of the 30−35 m3·min−1 primary flow, was dewatered using another drum microsieve. Dewatered back-wash water from this sieve was pumped to a sedimentation tank with a top surface area of 3.3 m2 and a volume of 5.5 m3. This system produced on average 0.7 L settled sludge containing ca. 10 % dry matter per kg of feed supplied. Sludge tapped from the bottom of the sedimentation tank was stabilised by mixing with lime. This system produced on average 0.7 L settled sludge containing ca. 10 % dry matter per kg of feed supplied. After stabilisation, the stored sludge was diluted with cattle manure and spread on agricultural land. The primary treated effluent was discharged into the receiving marine water body. The running costs of effluent and sludge treatment, including sieving, settling and stabilisation, amounted to US$ 0.056 per smolt produced, or about 5 % of the total production costs. In the recipient, no settled solids were detected on the seabed at the outlet point of the treated effluent.