A statistical approach is proposed to utilize the information contained both in scientific surveys and commercial fishing logbooks, in order to determine spatial and temporal distributions of recruiting and spawning fish of exploited populations. The approach is based on multivariate descriptive methods including ordination methods and classification techniques. A typology involving a principal component analysis (PCA), followed by a hierarchical ascending classification (HAC), is applied to both scientific and commercial data. PCA that accounts for spatial and temporal contiguities were performed. These analyses allow to compare structures observed at global and local scales, with those observed without focusing on a particular scale. The method is applied to the whiting population in the Celtic Sea. The analyses performed on both scientific and commercial CPUE show that most age groups are found north of 50°N. The analysis of commercial CPUE indicates four periods in the year associated with particular areas. High abundances of adults (age >2 years) are observed during spawning season (January–April) in inshore areas (south of Ireland and off Cornwall). Intermediate abundances of adults are observed in the same area in May and June. Between July and September, all age groups are observed in the Smalls area, where particularly high abundance of recruiting group 1 are found. During the last quarter, the distribution of adults is more widespread, mainly ranging between 51°N and 52°N.

The common carp is one of the main aquaculture species in the world. Despite this, most of the production is carried out using unselected strains. Selective breeding for fast growth has not proven to be effective in this species, but other traits (disease resistance, shape) could be successfully selected for. Most heritability estimates in the literature are unreliable due to environmental biases, but complementary results from population genetics and comparison of strains seem to indicate that there should be a potential for selective breeding in this species, including selection for growth rate, provided the base populations are variable enough (e.g. synthetic strains). New techniques such as parentage assignment with microsatellites and use of doubled haploid progenies may help describe much more accurately, without environmental bias, the genetic determination of traits of interest in the carp. This could be a new opportunity to design efficient breeding programs in this important species.

Lagoon fish communities often consist of complex assemblages of numerous species, difficult to manage with conventional stock assessment models. Useful data are still lacking for evaluating the importance of man-made disturbance and reference situations are missing, especially in developing countries. As a consequence, by analysing data collected 20 years ago in two of the six sectors of the Ebrie lagoon (Ivory Coast), this study aims to evaluate the impact of fishing effort on fish assemblages. These two sectors (V and VI), located far from the inlet, have similar physical, chemical, biological and fish fauna characteristics. The major difference lies in the fishing intensity: sector VI has a low fishing intensity (fishing for personal consumption using only individual gear), whereas sector V is heavily fished (professional fishing with both individual and collective gear, particularly beach seines which result in a considerably higher fishing effort). Comparisons between the two sectors were based on two complementary scientific approaches: a 3-year commercial fisheries survey (1978-1980) and a 1-year experimental survey (1981). The impact of fishing on fish assemblages is analysed through the main characteristics of fish populations and communities. The results show that there were major changes including an increased catch yield (37.5-189 kg ha–1 y–1), a lowering of fish diversity in catches, of fish biomass (100-20 kg ha–1), of average catch length (22.6-14.6 cm) and of trophic level of catches (26-58.5% of herbivore/detritivore species in total catches). Such results are quite unusual because they occurred even in non-overfished ecosystems: the fish assemblage was deeply modified in sector V compared to the lightly fished adjacent sector VI, even though fishing effort in sector V was only high but at a reasonable level. These data must be completed by similar studies in tropical lagoons with variable levels of fishing intensity in order to understand fish assemblage re-organization when submitted to stresses of different intensity.

Japanese cupped oysters suffer summer mortality in many culture sites along the French Atlantic coast. To ascertain whether mortality might be associated with morphological features of the shells, we estimated fluctuating asymmetry (FA) of hatchery/nursery-produced oysters kept in culture bags in the intertidal. FA is defined as random variations from a perfect symmetry plane (bilateral or radial) in some morphological trait. FA increases with disruption of homeostasy during ontogeny and has both genetic and environmental determinants. We found significant differences in FA between dead and live oysters in two of our three study groups. Therefore, lack of developmental stability may be involved in the summer mortality syndrome of oysters. We also found indirect evidence that once acquired, FA patterns of shells are retained at least partially. Since FA likely appears early during ontogeny and is recorded in the shells, we hypothesise that it might be useful for forecasting the ability of spat to resist environmental stress.

An estuary is an ecotone. It plays various vital roles in the functioning of the different fish species encountered. Each estuary has its own geographical, hydraulic, sedimentological and biological characteristics. These specific features influence the makeup and structure of the fish assemblages and the dynamics of the fish populations. The Gironde estuary is the biggest estuary in France and one of the largest in Europe. It is considered to be relatively unspoilt. The aim of this study is to provide an initial reference document on the specific composition of its fish assemblage. This study establishes a list of the fish species sampled by two different and complementary methods which have been regularly undertaken since 1979. A typology is recognized according to a series of ecological criteria. The relative proportion of fish species that spend all their life cycle in the Gironde estuary is very small. Moreover, the Gironde would appear to be the European estuary with the largest migratory amphihaline fish assemblage. Considering the study made by Elliott and Dewailly (1995), the Gironde estuarine fish population can be compared to those of 17 other European estuaries. The classification we obtained, raised a number of questions on the particularities of estuarine environment, with regard to ecological diagnostics and comparisons. Important points include the need for an inter-calibration of sampling practices, the relevance of taking into account the physical dimension of the environment (tidal range, upstream limit of saline intrusion, etc.), the degree of anthropogenic influence and its evolution.

La diversité spécifique est généralement considérée comme un facteur-clé de la résilience des écosystèmes en réponse à la pression anthropique et notamment à la pression de pêche. Dans cet esprit, on analyse ici l’impact de la pêche sur la diversité spécifique, à partir du cas des ressources démersales côtières de Guinée. Celles-ci ont la particularité d’avoir subi récemment un très rapide et important accroissement de la pression de pêche. En une quinzaine d’années, on est ainsi passé d’une situation dans laquelle les ressources démersales étaient considérées comme étant « à l’état vierge », à une surexploitation globale. Cette évolution mérite d’être considérée comme un « modèle accéléré » de l’histoire d’une exploitation. L’analyse se fonde sur les données de 18 campagnes scientifiques de chalutage démersal effectuées dans la zone côtière guinéenne entre 1985 et 1992. Le niveau de diversité spécifique, par campagne ou par trait de chalut, est quantifié par des indices synthétiques : la richesse spécifique, la diversité de Shannon et l’équitabilité. Les indices par trait de chalut sont analysés par les méthodes de modélisation en analyse de variance, afin de dégager une évolution temporelle des indicateurs. Les diagrammes rang/fréquence de chaque campagne sont également établis. On montre que les indices de diversité et d’équitabilité restent sensiblement constants, alors que l’abondance et la richesse spécifique diminuent significativement au cours de la période. Les espèces les moins abondantes et particulièrement des espèces de la communauté à Sparidés, tendent ainsi à disparaître des prélèvements. Enfin, l’année 1989 présente des indices de diversité faibles, liés à des conditions environnementales favorables pour certaines espèces entraînant un recrutement exceptionnel de celles-ci. La pertinence des indices utilisés est discutée.

Fish schools are known to take a large number of different shapes and dimensions, in such a way that defining a school from its morphology is still an unanswered question. Nevertheless, some school typology and classification has been done successfully in different areas of the world using vertical echo sounding data. This implies that some morphological patterns may correspond to or reflect behavioural specificities. The objective of this paper is to take advantage of the 3D exhaustive observation capabilities of multibeam sonar to extract the morphological and internal characteristics of tropical clupeid schools. The main parameters measured are geometrical properties (overall dimensions, volume, surface, etc.) and relative distribution of densities inside the school (heterogeneity, existence of nuclei, etc.). The main results show that a school is usually formed of one or several nuclei of high density connected by less dense parts, including empty areas (vacuoles). The dimension of these sub-units is highly variable, but remains inside a diameter of 5-20 m. The reliability of these dimensions is evaluated, and some thoughts on the behavioural mechanisms constituting schools are presented.

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.

Monthly variations in spatial and depth distributions, sex ratios, and maturity status in two species of hakes, Merluccius hubbsi and M. australis, were analysed in an area where their ranges overlap spatially on the shelf and slope around the Falkland Islands, and in international waters at 45–47° S (High Seas), using data collected by scientific observers on commercial fishing vessels. A variety of exploratory analyses were carried out on the raw data before patterns were quantified using generalised additive models. Both species use the areas studied as their feeding grounds. M. australis occur mainly on the Falkland shelf south of 51° S, whereas M. hubbsi is widely distributed throughout both the Falkland and High Seas shelf areas. Preliminary schemes of the seasonal migrations of both hakes in Falkland waters and on the High Seas are suggested and discussed. M. hubbsi and M. australis are found to be boldly segregated, both spatially and temporally, on their common feeding grounds, thus avoiding potential inter-specific competition for food resources.

Sungo Bay (China) has a mean depth of 10 m, a total area of 140 km2 and is occupied by several types of aquaculture, whilst opening to the ocean. The production of scallops (Chlamys farreri) cultured on long lines is estimated to exceed 50 000 tonnes (total weight) per year. Selection of sites for scallop growth and determination of suitable rearing densities have become important issues. In this study, we focused on the local scale (e.g. 1000 m) where rearing density, food concentration and hydrodynamics interact. We have developed a depletion model coupling a detailed model of C. farreri feeding and growth and a one-dimensional horizontal transport equation. The model was applied to assess the effect of some environmental parameters (e.g. food availability, temperature, hydrodynamism) and spatial variability on growth, and to assess the effect of density according to a wide range of hydrodynamical and environmental conditions. In the simulations, food concentrations always enabled a substantial weight increase with a final weight above 1.5 g dry weight. Compared to a reference situation without depletion, a density of 50 ind m–3 decreased growth between 0% and 100%, depending on current velocity when maximum current velocity was below 20 cm s–1. The mean ratio between food available inside and outside the cultivated area (depletion factor) varied with the percentage of variation in scallop growth that was due to density. Our model suggests that scallop growth was correlated with maximum current velocity for a given density and current velocity below 20 cm s–1. The model was integrated within a Geographical Information System (GIS) to assist in making decisions related to appropriate scallop densities suitable for aquaculture at different locations throughout the bay. Concepts (depletion), methods (coupling hydrodynamics and growth models), and the underlying framework (GIS) are all generic, and can be applied to different sites and ecosystems where local interactions must be taken into account.

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.

Turbot juveniles (45 g) were exposed for 41 d (17 °C, 34‰ salinity) to constant normoxic (100–100% air saturation, 100–100) or moderate hypoxic (75–75% air saturation, 75–75) conditions and to repeated hypoxic shocks (20% saturation for 1 h, 5 d per week) from normoxic (100–20% air saturation, 100–20) or moderate hypoxic (75–20% air saturation, 75–20) conditions. A normoxic group was feed restricted (100-FR). Mass increase of 100–100 and 75–75 groups fed to satiation was not significantly different. In comparison, it was significantly lower in the 100–20 and 75–20 groups (NS between the two hypoxic shocks groups). Intermediate results were obtained in the 100–100-FR group. The lowest mass increase under hypoxic shocks was explained by a significant decrease in both feed intake and food conversion efficiency (FCE). FCE was lower in the two hypoxic groups, but only the 75–20 group was significantly different from all the other groups. There was no sign of stress and no change in the physiological status of fish in any group. When challenged, pre-conditioning of turbot to regular hypoxic shocks extended survival time, slightly but significantly, for 50% of the population. It was 8 h longer in starved than in fed fish. When reared for 1 year in normoxic water, the growth rate of post-challenged survivors was dependent on pre-conditioning: day 0–375 specific growth rate was significantly higher in the two groups acclimated to repeated hypoxic shocks. In the second experiment, it was shown that exposure to 20% air saturation for 12 h led to major physiological changes within 4 h: a significant decrease in plasma total CO2 and increase in plasma lactate contributing in maintaining blood pH stable, and a significant increase in osmolarity and chloride concentration. When returned to normoxic water, the recovery capacity of the fish was high: plasma osmolarity and total CO2 returned to pre-exposure levels within 1 h. The results are discussed in terms of turbot capacity to cope with repeated hypoxic shocks and to acclimate.

The Latin American shrimp Litopenaeus stylirostris was introduced in three different Pacific islands (Tahiti, New Caledonia via Tahiti, and Hawaii) and hatchery-propagated for 7–25 generations to develop shrimp farming based on these domesticated stocks. Three microsatellite markers have been used in an attempt to assess the genetic bases of the populations available to start a selective breeding program. The comparison of eight hatchery stocks (five New Caledonian, two Hawaiian and one Tahitian stocks) and one wild Ecuadorian population showed a much lower variability in the domesticated stocks than in the wild population, especially in New Caledonia and Tahiti (2–3.7 vs. 14–27 alleles per locus; 20–60% vs. 90% expected heterozygosity). The Tahitian and the New Caledonian stocks share the same alleles, suggesting that the loss of alleles occurred during the common past of these populations. On the contrary, New Caledonian and Hawaiian populations share only one common allele at the three loci studied. Although the low genetic variability and the resulting inbreeding of the New Caledonian stocks do not seem to affect their present performance, the results of this study demonstrate the usefulness of the introduction of new stocks in order to increase the potential responses to new controlled or uncontrolled selective pressures. The introduction in New Caledonia of the Hawaiian domesticated stocks, which would provide the local shrimp industry with 40% of the allelic diversity of the species, is advised and preferred to the one of wild animals in order to take advantage (i) of the spontaneous selection which occurred during domestication and (ii) of their favourable sanitary "specific pathogen free" status (no presence of four viruses: WSV, YHV, IHHNV, TSV) which limits the risk of introduction of pathogens.

The first successful case of transgenic fish was achieved in 1984. It is in a model system that the integration and expression of recombinant human growth hormone (hGH) in host red common carp (Cyprinus carpio, red var.) have been thoroughly studied. Recently, the integration sites have been recovered and characterized. Compared with non-transgenic peers, hGH-transgenic fish are prior in dietary utilization and growth performance. In view of bio-safety and bio-ethics, an "all-fish" construct CAgcGH, grass carp growth hormone fused with common carp β-actin promoter, has been generated and transferred into Yellow River carp (C. carpio, local strain in Yellow River) fertilized eggs. Under middle-scale trial, CAgcGH-transgenics show higher growth rate and food conversion efficiency than the controls, which is consistent to laboratory findings. To avoid the potential impact of transgenic fish on the environment, a sterile strain of transgenic triploid fish has been successfully produced. The "all-fish" transgenic common carp is also approved safe enough as daily food, according to a test based on the pathological principles of new medicines issued by the Ministry of Health of China. The "all-fish" transgenic common carp with growth enhancement is now ready for market, but looking for governmental authorization.

Standard geostatistical techniques provide effective methods for estimating the global abundance and precision of a variable of interest, for mapping its spatial distribution and for describing its spatial structure. In the case of acoustic survey data, however, obtaining a measure of precision of the global abundance estimate is confounded by the combination of variances from the interpolation of both the acoustic data and the concomitant fish length data. Even if the global estimation variance could be calculated, the distribution of the estimation error is not known and so confidence intervals cannot be determined. Furthermore, kriged distribution maps, in minimising the estimation variance, tend to smooth out local details of the attribute’s spatial variation: small values can be overestimated and larger ones underestimated, such that the kriged map is smoother than reality. This can lead to serious shortcomings when trying to detect patterns of extreme attribute values, such as the high densities encountered in some fish schools. Stochastic geostatistical simulations, conditional on sampled locations, provide a solution to many of these problems. They can deliver a measure of uncertainty for local (density) estimates, a confidence interval estimation for the global mean density, and finally, reproduce global statistics, such as the sample histogram and variogram. In so doing, they also provide maps of the attribute, which are spatially realistic because the variogram is reproduced; these are generated as a number of equiprobable realisations. In the present paper, we apply these techniques to acoustic data from an acoustic survey of North Sea herring. Sequential gaussian simulations are used to generate realisations for fish length and values of the nautical area scattering coefficient. These are then combined to produce realisations of herring density. The combined set of multiple realisations is then used to provide confidence intervals for the global abundance estimate: 95% of the herring abundance estimates are between 5677 and 6271 millions of individuals. Although the method presented in this paper contributes to the assessment of total uncertainty for acoustic surveys, the approach may have suffered from bias due to the use of off-the-shelf data transformation algorithms on fisheries acoustic data, which are often very positively skewed. We discuss this limitation and propose corrections for future work.

This study was based on wild-caught blacklip abalone Haliotis rubra L., from Port Fairy waters, south eastern Australia (142°15'E; 38°21'S), from July 1998 to November 1999, and was initiated to evaluate the spawning season and other aspects of its reproductive biology. The shell length and body weight of female and male abalone sampled ranged from 12.0 to 18.6 and 12 to 15 cm, and 137 to 529 and 148 to 585 g, respectively. The sex ratio did not vary significantly from 1:1 through the year. The gonadosomatic index (GSI) ranged from 3.0% to 8.4% in males, and 2.5% to 14.1% for females, and the highest GSI as well as the highest proportion of mature animals were recorded from September to October. During these months the hepatosomatic index (HSI) was low, and an inverse correlation between GSI and HSI (P < 0.05) was evident. Fecundity of blacklip abalone ranged from 1.09 to 7.5 million eggs for females of 12–14.5 cm in length, and 115–487 g in total body weight, respectively. The lipid content of the female gonad increased significantly from about July to November, and an opposite trend was observed for lipid content of the digestive gland. Seasonal changes in the protein and ash contents of the gonad and/or the digestive gland were not always significant.

We tested the hypothesis that along with gill Na+K+ATPase activity reduction, branchial energetic metabolism of brook charr (Salvelinus fontinalis) is altered during sexual maturation. Maturing and sterile fish were transferred from freshwater (FW) to seawater (SW). The activity of gill pyruvate kinase (PK), cytochrome C oxidase (COX), citrate synthase (CS) and lactate dehydrogenase (LDH) was measured at different intervals. Following 1 month in SW, twofold increases in Na+K+ATPase activity were recorded in all groups, while mean metabolic enzyme activities were sharply reduced (COX: 0.051 ± 0.029 to 0.036 ± 0.018; PK: 1.670 ± 0565 to 1.210 ± 0.340 LDH: 2.245 ± 0.690 to 1.642 ± 0.381 μmol mg–1 protein min–1). Interestingly, during this period, no mortality occurred. After 5 months, comparison of Na+K+ATPase:CS and Na+K+ATPase:LDH ratios of mature and sterile fish held either in FW or SW, indicated that the response of Na+K+ATPase largely exceeds the response of the metabolic enzyme apparatus in hyperosmotic conditions. Hence, the reduced iono-osmoregulatory capacity and higher mortality observed in SW-maturing fish during the reproductive season appears to be mainly attributable to Na+K+ATPase activity reduction rather than the alteration of gill metabolic capacity, since no concurrent increase of metabolic enzyme activity with Na+K+ATPase activity occurred.

Piracanjuba (Brycon orbignyanus) is a Brazilian migratory fast-growing omnivore, very appreciated as a sport fish, which is threatened to extinction in Southern Brazil due to stock over exploitation and dam building. Therefore, efforts have been made to raise this fish in captivity for reintroduction and aquaculture purposes. In the present study, the effects of different dietary protein and lipid concentrations on piracanjuba fingerlings growth performance, feed utilization, body composition, hepatosomatic index (HSI) and activity of the lipogenic enzymes fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (G6PD) and malic enzyme (ME) were investigated using a 2 × 3 factorial experiment. Six casein–gelatin based diets were prepared combining two protein (30% and 32%) and three lipid concentrations (5.5%, 8.8% and 12.1%). Eleven fish, average weight 11.30 ± 0.1 g, were held in each of 18100–l aquaria, supplied with recirculating freshwater. Each diet was randomly assigned to triplicate groups of fish and fed to apparent satiation, twice a day for 100 d. Piracanjuba fingerlings' daily weight gain (0.36–0.40 g), specific growth rate (1.43–1.51%), feed utilization and HSI were not influenced by dietary protein or lipid concentration. However, body composition was directly affected by dietary treatment. An increase in body fat and dry matter was observed as dietary lipid increased, for both dietary protein concentrations tested. The activity of FAS was depressed by increasing dietary fat levels but the G6PD activity did not differ among dietary treatments, although ME activity showed some regulation by dietary protein. These results indicate that an increase from 5.5% to 12.1% in the dietary lipid, at a dietary protein concentration of 30% or 32%, promotes body fat accumulation in piracanjuba fingerlings with no improvement in growth, suggesting that the lipid requirement for this species should be 5% or less, when raised for commercial purposes. However, the additional energy reserve from body fat accumulation could be desirable for piracanjuba fingerlings produced for stock enhancement.

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.