Taking into account that the relationship between metabolic substrate and the characteristics of the diet is essential for understanding the mechanisms associated with the use of the components of a certain food substance, the aim of this study was to examine the metabolic substrate used by Penaeus setiferus, P. schmitti, P. duorurum and P. notialis postlarvae PL 35–40 (35–40 days after metamorphosis) fed purified diets with different levels of proteins (40, 50, 60 and 65%). Oxygen consumption and ammonia excretion were measured in animals in intermoult which had been acclimatized to each diet over a minimum of 5 days. Measurements were taken on fasted (24 h) and fed animals. Oxygen consumption of fasting animals increased with a rise in the proteins of the diet in the four species. In the fed animals, this tendency was observed in P. setiferus and P. notialis, while in P. schmitti and P. duorarum oxygen consumption was a weak relationship, decreasing or increasing with a diet with 50% protein. Both in fasting and feeding animals, the ammonia excretion increased with the increase in proteins in the diet. The O : N atomic ratios of the four species decreased (between 30 and 3), according to increase in dietetic protein : energy ratio, (10.4 to 17.0 mg protein/kcal). The highest value of O : N ratio was observed in P. setiferus (40% of protein requirement, O : N = 24 to 34) and lowest in P. schmitti (60% of proteinrequirement, O : N = 4 to 11), with intermediate values in P. duorarum and P. notialis (50% protein requirement, O : N = 8 to 14 and 13 to 19, respectively). These results support previous research that showed that the omnivorous-herbivorous species, like P. setiferus, use protein-lipids normally as energy source in contrast to omnivorous-carnivorous species such as P. duorarum which use protein preferentially as a source of energy.

Retention of the second polar body for the production of triploid Arctic charr (Salvelinus alpinus) was induced by 65 MPa (650 bar) pressure shocks applied 30, 40 or 50 min after fertilization, each shock lasting 5 min. Triploid yield (percentage of relative survival to control × percent triploidy) varied from 55 to 100 % and it was generally superior to 80. Despite increased mortality and decreased growth in diploid charrs during the spawning period, growth and survival did not differ between diploid and triploid Arctic charr up to and during their third year of life. Most of the triploid males had developed testis, but they did not render milt; few triploid females had developed ovaries. Fecundity of triploid females was low and fertilized eggs from triploid females did not hatch.

Two groups of sea bass (mean initial weight 78 and 250 g) were given for 23 weeks a commercial diet, whose composition was modified or not (control). The modified diet was: — supplemented with highly oxidized fish oil, — poorly supplemented with ascorbic acid, — not supplemented with butylated hydroxytoluene, DL-alpha-tocopheryl acetate and choline. At the end of the experiment, fish fed the modified diet displayed skeletal muscle degeneration, decreased red blood cell count, haemoglobin content and haematocrit, and increased crythrocyte fragility and plasma enzyme activity (aspartate aminotransferase and creatine kinase). Simultaneously, low DL-alpha-tocopheryl acetate levels and increased amounts of thiobarbituric acid-reactive substances were observed in muscle and liver. On the other hand, growth disorders, liver lesions, changed plasma enzyme activity (alanine aminotransferase, glutathione peroxydase), or altered conjugated dienes in perivisceral fat were not evidenced. The pathological observations were more pronounced on the smaller fish group, but the disease could already be detected by measuring haematological and biochemical criteria, the interest of which in the diagnosis of such nutritional disease is discussed.

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.

Three species in the group of "small" Barbus from West Africa were analyzed by enzyme electrophoresis to assess their genetic differentiation. Comparison with a species of "large" Barbus from the same region showed that the "small" Barbus are certainly diploid and the "large" tetraploid. They clearly form two distinct lineages. Phenetic dendrograms (Nei distances) and cladograms (compatibility networks) of the genus Barbus are proposed, based on three African diploid species, two diploid species from Saudi Arabia and Southeast Asia, one African tetraploid species, and two French tetraploid species. These trees reveal two sets of species, i.e. diploid and tetraploid. Several methods of data processing are suggested for overcoming the difficulties involved in simultaneously analyzing species with different ploidy levels.

Contamination of shellfish by paralytic shellfish poisoning (PSP) toxins poses an economic threat to shellfish farmers. As contaminated shellfish cannot be harvested for long periods of time, it would be very useful to develop processes to optimise and shorten their detoxification. In this study, Pacific oysters Crassostrea gigas were first experimentally contaminated over a period of 13 days with a continuous flow of toxic Alexandrium minutum cultures at concentrations ranging from 150 to 200 cell ml-1 (toxin content after 13 days of contamination 438 $\mu $ g STX equiv. 100 g−1 wet weight). Then, two different detoxification treatments were tested and showed detoxification rates greater than those observed in coastal environments. The first treatment consisted of feeding oysters on Skeletonema costatum, at a concentration of 2000 cell ml−1 to speed up detoxification rates. The second detoxification method used the same Skeletonema costatum diet, supplemented with silt particles at a concentration of 20 mg L−1. A control was also set up by placing contaminated oysters in seawater with no additional algal food. The detoxification experiment lasted 8 days. Toxin contents were analysed by liquid chromatography with fluorescence detection (LC-FD). The S. costatum diet significantly reduced the time needed for oysters to reach the sanitary threshold (80 $\mu $ g STX equiv. 100 g−1 wet weight), but no effect of the silt supplement could be demonstrated conclusively. These different detoxification methods did not influence toxin biotransformations as observed in oyster tissues, i.e. epimerisation and decarbamoylation of gonyautoxins 2 and 3.

Pacific oysters and king scallops placed individually in a recirculating flume were fed for 2 weeks with a constant concentration (120 cell ml–1) of a toxic strain of Alexandrium minutum. Fluorescence at the outlet of each experimental unit was measured continuously, and biodeposits were recovered twice daily to evaluate feeding time activity (FTA) and rates of organic filtration (OFR), ingestion (OIR) and organic absorption (OAR). Ion-pairing high performance liquid chromatography (IP-HPLC) was performed concurrently to quantify paralytic phycotoxins both (i) individually in shellfish at the end of the contamination period and (ii) in A. minutum cultures to estimate cellular toxin concentration. These data allowed comparison of the actual tissue toxin concentration (TOX) with the theoretical toxin accumulation rate (TAR) calculated from the linear relations between OAR, cell number, fluorescence and cell toxicity. The results show high FTA/TAR and FTA/TOX correlations (R2 = 0.78) for both oysters and scallops. The TAR/TOX relation, though not yet clearly defined, suggests the minimum quantity of absorbed toxin at which the accumulation process is induced.

A method is presented to estimate and diagnose the sources of uncertainty in acoustic survey measures of fish density. The method involves simultaneous Monte Carlo simulation of density and uncertainty resulting from imprecision in all terms in acoustic analyses. Known bias can also be considered. Results are presented from theoretical simulations based on assumed distributions of fish density and acoustic parameters at sample sizes from 10–1000, and on survey data for Atlantic cod and redfish. Uncertainty can be reduced by either increasing the sample rate or by decreasing the error in input variables (system and ocean parameters, backscatter, target strength, species identification, detectability). Uncertainty in inshore cod surveys in Newfoundland waters can be attributed for the most part to heterogeneous fish distribution and detectability variance (total R2 = 0.64). Uncertainty in offshore redfish surveys is attributed to heterogeneous fish distribution, and variance in target strength and species identification (total R2 = 0.82). Uncertainty can be reduced by survey design, not only by the classical methods of achieving less diverse measures of backscatter, but also by increasing precision in the input parameters to the density estimate, in particular, target strength, detectability, and species identification.

In the Chausey archipelago, growth of the burrowing bivalve Venus verrucosa(Mollusca: Veneridae) has been shown to be highly variable between closelylocated sites (<1 km). To explain this small-scale spatial variability, we tested thetrophic hypothesis using both fatty acid markers, and carbon and nitrogen stable isotopes(δ13C and δ15N). Environmentalparameters, including substrate, were also analysed to discriminate their effects onpotential trophic differences. Results of isotopic fractionation and lipid profiles ofwater column and digestive gland samples both showed a large contribution of phytoplanktonto the diet of V. verrucosa. More surprisingly, the same results suggestthat Phaeophyceae and Rhodophyceae macroalgae could contribute to the nutrition ofV. verrucosa as dissolved exudates. Whereas site differences were notobserved between the food sources of V. verrucosa, we showed that growthperformance index was correlated to wave height. Thus, we hypothesized that the high localgrowth variability could be controlled by the hydrosedimentary dynamics. In addition,although no significant growth differences were found between intertidal and subtidalpopulations, better condition index and more total lipids were found in the digestivegland of intertidal V. verrucosa, suggesting potential compensatorygrowth mechanisms.

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.

Fin condition was examined in 100–500 g hatchery-reared rainbow trout sampled in a large range of environmental conditions of an experimental farm. A method that is simple to use, requires little training, and does not need costly sophisticated equipment or reference to a model is proposed to assess fin erosion (defined as a decrease in size and profile alteration of fins). A procedure to reliably measure the length of the longest ray present in two selected fins (dorsal and pectoral) is described. Fin general profile is assessed using five levels of erosion based on the precise rank of intact or eroded rays to limit subjective bias. The suitability of the two descriptors of fin erosion under laboratory, farm or field conditions is discussed.

The aim of this report is the synthetic presentation of observations related to ultrastructural aspects of the lipid metabolism during the ontogenesis of trophic mechanisms in three teleost species, the sea bass, Dicentrarchus labrax, the sea bream, Sparus aurata and the pike-perch, Stizostedion lucioperca. The results have shown the respective roles of the vitelline syncytium, the intestine, the liver and the exocrine pancreas during the change from an endogenous lipid source, the yolk vesicle, to an exogenous lipid one, food. They make it possible to stress the close correlation between the development of the biliary function, that of the exocrine function of the pancreas and that of the intestinal absorption of lipids. These activities established during the endotrophic stage are slight at the beginning of trophic life and then increase at the end of the endo-exotrophic stage. Analysis of the results suggests the occurrence of four physiological phases characteristic in early lipid metabolism establishing the main heads in acquisition of the trophic autonomy according to a pattern similar to that of mammals.

The paper describes the main drawbacks in the application of conventional acoustics in shallow waters, and reviews the advantages and limitations that existing multibeam sonar present in these ecosystems. New techniques and methods for adapting multibeam sonar to shallow waters are proposed and discussed. A method for analysing acoustic data from shallow waters through image analysis process is presented and some examples are considered. The results show that scattered fish can be observed individually and counted, and that schools are described in their morphology and behaviour. From these results an ‘ideal’ acoustic device is defined: a sonar operating at more than 400 kHz with a coverage of at least 120° in one direction and, depending on the needs of the user, 15° or 1° (which can be modified easily) in the perpendicular plane. The beam opening–angle is 0.5° in the centre beam, increasing to 1.0° at the 60° steer–angle, giving a total of 240 beams. Multibeam sonar data could be used for several purposes in shallow waters, in particular to estimate fish density and biomass, and study spatial and temporal behaviour of fish.

In order to monitor the recovery of vegetation from pollution and the success of re-seeding efforts, acoustic echoes from the sea floor, covered and uncovered by underwater vegetation, were collected in Puck Bay (southern Baltic sea) using a 208 kHz Biosonics DT 4200 scientific echo sounder. The echo envelopes were examined and several of their parameters were recommended for further analysis. The possibility of using these parameters to distinguish between a bare sea floor and underwater meadows was tested. The parameters may be helpful in the identification of the species composition of the meadows and in accurate biomass assessment.

This paper presents the simulator SHADYS (‘simulator halieutique de dynamiques spatiales’). SHADYS is a tool devoted to the representation of spatial processes involved in fisheries dynamics. It puts together three fundamental entities in an explicit spatio-temporal way: the environment, the fish populations under consideration and the fishing fleet. It is based on simple, realistic and well identified mechanisms (density-dependent habitat selection, advection and diffusion of a fish population, fishermen search strategy, etc.) implemented by interfacing numerical models with a GIS (geographic information system). As a virtual laboratory, SHADYS allows experiments to be performed in a theoretical world, such experiments being generally impossible to perform in reality. As an illustration, different scenarios of a marine refugia-based management have been explored using the SHADYS simulator. Different simulations are conducted to assess the short-term effects on yield of a marine protected area. It is shown that for diffusive or migratory species, the yield per recruit as a function of the protected surface can reach a maximum. Under this condition, the concept of ‘space overfishing’ is meaningful. Protected areas then behave like ‘sources’ and exploited areas like ‘sinks’. For resident populations, the larger the protected area is, the lower the catches per recruit are. Regarding the spatial distribution of the fishing effort, it is shown that if it is spatially distributed in order to maximize catches, then fishing boats will slowly tend to be distributed all along the boundaries of the protected area.

Radio tracking has been extensively used to enhance our knowledge on the movement and home range of fish in general and salmonids in particular. However, the use of various temporal sampling protocols is likely to overlook fish movements, and produce experimental artefacts, the amplitude of which is unknown and may compromise comparison of fish behaviours revealed by different protocols. Starting from a day-by-day tracking study of brown trout in Belgian waters (Aisne stream, nine fish, minimum 39 daily locations per fish), we re-examined their home range and mobility, through a subsampling process, as if the fish had been located at longer time intervals (2–14 days). The estimates from subsamples were compared to the original data set in order to quantify the corresponding reduction of accuracy from observed data, and how far this could be predicted on the basis of locating frequency. The results clearly indicate that all intervals longer than one day generally generate substantial biases (reduction of accuracy from 0 to 82% for home range and from 5 to 92% for mobility) but these can be partly corrected through the use of predictive models. This analysis demonstrates that any comparison between studies relying on different locating frequencies can generate some ambiguity when interpreting biological phenomena or geographical differences.

Tilapia species are generally characterized by a large tolerance to salinity; however, such capacity to adapt to brackish or seawater may be modulated by environmental factors. The major osmoregulatory mechanisms involved in salinity adaptation are presented. Most of the available data concern the role of gills in salt or water exchange. The importance of different factors (environmental or endogenous) in such adaptation is also discussed. The second part presents a survey of the endocrine control of osmoregulation in tilapia. Both fast-acting (e. g. glucagon, urotensins, catecholamines) and long-acting (e.g. prolactin, cortisol) hormones have been studied. In conclusion, several areas of osmoregulatory physiology potentially interesting for aquaculture are discussed.

The Sydney rock oyster (Saccostrea glomerata) (SRO) is an oyster species that only occurs in estuaries along Australia’s east coast. The SRO industry evolved from commercial gathering of oyster in the 1790s to a high production volume aquaculture industry in the 1970s. However, since the late 1970s the SRO industry has experienced a significant and continuous decline in production quantities and the industry’s future commercial viably appears to be uncertain. The aim of this study was to review the history and the status of the SRO industry and to discuss the potential future prospects of this industry. This study summarised findings of the existing literature about the industry and defined development stages of the industry. Particular focus was put on the more recent development within the industry (1980s-present) which has not been covered adequately in the existing literature. The finding from this study revealed that major issues of the industry are linked to the management of prevailing diseases, the handling of water quality impairments from increasing coastal development, increasing competition from Australia’s Pacific oyster (Crassostrea gigas) industry and the current socio-economic profile of the industry. The study also found that policy makers are currently confronted by the dilemma of saving a “dying art”. Findings from this industry review may be vital for current and future fisheries managers and stakeholders as a basis for reviewing industry management and development strategies. This review may also be of interest for other aquaculture industries and fisheries who are dealing with similar challenges as the SRO industry.

The temperature evolution over the past 40 years in the Bay of Biscay (North-East Atlantic) is investigated from an in situ data analysis, completed with a satellite SST (Sea Surface Temperature) analysis over the last 20 years. The in situ dataset is an interannual version of the BoByClim climatology, covering the Bay of Biscay area with a 10-km horizontal resolution and a 5-m vertical step. The satellite dataset is the European COastral Sea Operational Observing and Forcast System Program (ECOOP) daily analysis, covering the IBIROOS (Iberian-Biscay-Irish Sea) area with a 4-km resolution. The study area (43°N-50°N/12°W-1°W) extends over the intersection of the domains covered by these two analyses. In the 0–200 m layer of this domain, a heat budget has been computed from an ocean circulation model over the period 1965-2004. Heat is essentially imported from the west by the North Atlantic Drift, then exported southward and northward, or transferred downward into deeper layers. The annual average of air-sea flux is weak, with a zero isoline crossing the domain from the northwest to the southeast. Ocean and atmosphere, forming a coupled system, have comparable contributions and may both result in a heat sink or source. At the interannual scale, variability is mainly controlled by the air-sea flux, with a secondary contribution from oceanic transport. A strong warming of $\sim $ 0.2 °C/decade for the period 1965-2004 is apparent from the surface down to the 200-m depth. The decadal evolution is consistent with several analyses over the North Atlantic. Meanwhile, warming is approximately twice faster than in the whole basin. This trend is not steady, as a cooling period occurred until the early 1970's, and the temperature increase has been significantly stronger during the last 20 years ( $\sim $ 0.3 °C/decade between 0 and 100 m, from 1986 to 2005). The trend and the interannual variability are maximal over the northern part of the shelf. The typical duration of interannual anomalies is two years and their penetration depth is ~100 m, although they occasionally exceed 200 m. The interseasonal anomalies are also stronger within the mixed layer (root-mean-square, RMS = 0.6 °C at the surface) than below (RMS = 0.3 °C at 100 m). Their geographic distribution is radically different between the surface and the deep levels. A seasonal dependence of the warming rate is evident in the upper layer, as the temperature trend is stronger in summer than in winter (by a factor of 2 at the surface). Some of the potential implications for the ecosystem are discussed, particularly in terms of species distribution and dynamics of species exploited by fisheries.

This paper critically reviews the theoretical and practical implications of adopting the original ‘ecological footprint’ concept as an index of the sustainability of aquaculture production systems. It is argued that the concept may provide a reasonable visioning tool to demonstrate natural resource dependence of human activities to politicians and the public at large. However, due to its inherent weaknesses, the ‘ecological footprint’ fails to provide a cohesive analytical tool for management. From an ecological perspective, its two-dimensional interpretation of complex ecologically and economically interacting systems is one major weakness. From an economic perspective, the ‘footprint’ fails to recognise factors such as consumer preferences and property rights which have a major influence on the allocation and sustainable use of resources. The interactions among social, ecological and economic factors are discussed in an attempt to foster a broader inter-disciplinary view of criteria required for a sustainable use of aquatic resources.