We analysed spatial and temporal patterns of condition factor (CF) of sprat (Sprattus sprattus) between 1986 and 2000 in different areas of the Baltic proper. Results showed a moderate increase in CF between 1986 and 1989. Afterwards, an abrupt decrease in CF, between 22% and 29%, occurred in all the areas of the Baltic proper. However, from 1998 and onwards, CF increased compared to the previous years. Weight-at-age and CF of Baltic herring showed a similar pattern in the same period. Several factors affecting variability of sprat CF were evaluated. Data showed that sprat CF was density-dependent and possibly related to the pelagic fish abundance and individual food intake. Temperature did not influence sprat CF while salinity seemed to affect variability of sprat CF in the northern Baltic proper. Changes in salinity levels may shape pelagic fish growth rates both indirectly changing the zooplankton community structure and abundance and/or directly via fish physiology and metabolisms.

The development of acoustics tools and methods for monitoring anthropized ecosystems represents a new field for the application of acoustics. Monitoring such an environment was not possible with single vertical echo sounders, due to the fact that the artificial structures and the natural targets were not distinguishable. Monitoring data were collected along the French Mediterranean coastline, during five short surveys of mussel culture longline areas. Both the Reson Seabat 6012 multibeam sonar (455 kHz) and the Simrad SR 240 omnidirectional sonar (23.75 kHz) were used for target detection. The former tools allow accurate allocation of the different types of echoes to artefacts, fish schools and scattered fish. The school characteristics collected included morphological, geographical (GPS, school location), and behavioural (connections with the longlines). An acoustic survey undertaken with the same hardware near the study area allowed the comparison of fish schools and the TS distribution of individual fish in the open sea and in the mussel area. These data permitted us to evaluate the ecological impact of a mussel culture on the ecosystem, in a context of predation behaviour of fish on these longlines. Finally, the acoustic data revealed the configuration of each concession and the level of charge of each line. We discuss the applicability of this technology for in situ real time monitoring for joint management of such ecosystems. The information can allow littoral cooperative management or incorporating it into an ecosystem approach.

Pearl oyster grafting is a complex surgical operation that should lead to pearl formation after approximately eighteen months. Although this technique has been used for many years in French Polynesia, the grafting process is still not standardised. While studies have been carried out in order to improve graft performance and yield, these remain highly variable due to post-grafting mortality, nucleus rejection and unreliable pearl quality, all of which constrain pearl farm profitability. The present study uses histological analysis to monitor oysters that either rejected or retained their nuclei. Both groups of oysters are compared in terms of evolution of the graft, which could influence retention, and the development of a pearl sac in cases where grafting was successful. Data show that rejection phenomena are linked to a number of causes, notably an inflammatory reaction in the “receiving” oyster, the presence of numerous tissue lesions and the quality of the grafted tissue. These results suggest that study is needed on the different concomitant elements of the grafting process: the graft “donor” oysters, the nucleus and the “receiving” oyster and their interactions.

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.

From April 1995 to April 1996, the annual reproductive cycle of male Eurasian perch Perca fluviatilis was studied at the Lindre Center (Moselle, France). At monthly intervals, five males (mean body weight of 133 ± 43 g and total length of 175 ± 9 mm) were caught. From sampled organs, the gonadosomatic (GSI), hepatosomatic (HSI) and viscerosomatic indexes (VSI) were calculated and plasma testosterone (T) and 11-ketotestosterone (11KT) levels were measured. After the spawning period in mid-April, GSI and HSI dropped and VSI increased to 3.8 ± 0.1 %. In September, GSI reached its maximum (8.5 ± 1.8 %). At this time, spermatocytes, spermatids and spermatozoa were abundant, whereas in June only spermatogonia were observed. During winter, GSI was stable at approximately 5 %, HSI reached its maximum (1.9 ± 0.3 %) and VSI was low (2.6 ± 0.2 %). From April to November 1995, plasma T and 11KT concentrations were low (< 0.5 ng·mL–1). Plasma T levels increased significantly in December and reached peak levels (12.3 ± 2.1 ng·mL–1) in January, then decreased in February and increased again until spawning in April (6.8 ± 2.1 ng·mL–1). This second elevation could be related to the beginning of a new spermatogenic cycle. Plasma levels of 11KT increased significantly from October to February 1996 (4.9 ± 1.1 ng·mL–1). From February to the spawning period (April 1996), plasma 11KT decreased significantly, but values were significantly higher than those measured in fall. Males were spermiating from January to spawning in April.

This study describes the current status of the small fish community in Niushan Lake in China, and examines the spatial and seasonal variations of the community in relation to key environmental factors. Based on macrophyte cover conditions, the lake was divided into three major habitat types: (1) Potamogeton maackianus habitat, (2) Potamogeton maackianus and Myriophyllum spicatum habitat, and (3) uncovered or less-covered habitat. Fish were sampled quantitatively in the three habitat types by block nets seasonally from September 2002 to August 2003. A total of 10 469 individuals from 27 fish species were caught, among which 20 species were considered as small fishes. Rhodeus ocellatus, Paracheilognathus imberbis, Pseudorasbora parva, Micropercops swinhonis and Cultrichthys erythropterus were recognized as dominant small fishes according to their abundance and occurrence. It was noted that (1) small fishes predominated the total number of fish species in the lake, which reflected to some degree the size diminution phenomenon of fish resources; (2) many small fishes had plant detritus as their food item, which was consistent with the abundance of macrophyte detritus in the lake and implied the importance of detritus in supporting small fish secondary production. Canonical correspondence analysis suggested that the spatial distributions of most small fishes were associated with complex macrophyte cover conditions. Macrophyte biomass was positively correlated with species richness, diversity index and the catch per unit of effort (CPUE) of the fish community. Water depth had no significant effects on species diversity and distribution of the small fishes. Correspondence analysis revealed a higher occurrence of the small fishes and higher abundance of individuals in summer and autumn. Seasonal length-frequency distributions of several species indicated that more larval and juvenile individuals appeared in spring and summer. This study provides some baseline information which will be essential to long-term monitoring of small fish communities in the Yangtze lakes.

Siluriformes, as well as Characiformes and Cypriniformes, are a diverse and widespread group of Ostariophysan fishes, but Siluriformes have a probable ancestral benthic feeding habit. They have a unique suite of morphological, physiological, ecological and behavioural traits that equip them to succeed in freshwaters but only to a limited extent in the sea. They are typically, non-aggressive stalking predators that hunt at night or in turbid water using primarily nonvisual sense organs, although there are many exceptions. The modification of the Weberian apparatus for sound production has probably resulted in some loss of buoyancy control. Catfishes are represented in all the dillerent breeding guild categories and exhibit diverse and sometimes bizarre breeding methods. Catfishes tend towards the altricial end of the altricial-precocial life-history continuum. Only two families (Ariidae and Plotosidae) have successfully colonised the sea; physiological constraints and strong competition from Elasmobranchii and Actinopterygii fishes are probable reasons, and it is notable that the two families that have succeeded have precocial lire histories that are more suited to highly competitive environments.

The development and application of genomics has been facilitated in a number of fields by the availability of new methodologies and tools, such as high throughput DNA sequencing and complementary DNA (cDNA) microarrays. Genomic tools are already used in research on commercially important fish and shellfish species. Thousands of expressed sequence tags (EST) are now available for some of these species, and the sequencing of complete genomes of tilapia, cod, salmonids, flatfishes, sea bass and Pacific oyster has been proposed. Microarray technology through simultaneous analysis of the expression of thousands of genes allows the identification of candidate genes involved in the function of multiple physiological, morphological and behavioural traits of interests in organisms and populations from different environments. This paper reviews the current development of genomic technologies, and pinpoints their potential beneficial applications as well as implications for fisheries management and aquaculture.

Mussel (Mytilus galloprovincialis) plasma contains cytotoxic activity against both vertebrate (erythrocytes and mouse tumour) and protozoan cells. Procaryotes (Escherichia coli and Vibrio alginolyticus) were not sensitive to the cytotoxicity. The activity was still present in dialyzed samples but was inhibited by heating at 45 °C. Large individual variability which was not correlated with protein concentration and an increasing number of reactive specimens following injection, suggested that naive mussels were in various stages of immune response. Purification by anion exchange chromatography followed by gel filtration revealed a 320 kDa cytotoxic polymeric protein that acts through a polymerization process after binding onto target cell membranes as revealed by ultrastructural observation.

European and Pacific oysters (Ostrea edulis and Crassostrea gigas) expressed antibacterial activity against both Gram negative and Gram positive bacteria which was most probably due to small proteins. When tested against the marine pathogenic Vibrio alginolyticus, hemocyte lysates of both species were more active than cell-free plasma. Antibacterial activity showed significant individual variability that was dramatically reduced by stimulation through mechanical stress or injection. The number of spontaneously active Pacific oysters increased from 50 to 100% following a single injection of bacteria.

These results strongly support the view that bivalve molluscs possess sensitive immuno-defense mechanisms that will greatly aid the development of aquaculture systems by employing refined techniques of transgenesis.

Individual transferable quotas (ITQ) were implemented in the Tasmanian red rock lobster fishery in 1998 and ten years later we assessed the impacts on the fishery. Particular attention was devoted to investigating the performances of the fishery with regard to three features identified as major impacts in the literature: rationalization of the fishing fleet, change in fishing strategy in order to maximise the fisher's profit and concentration of fishing rights and activity. On average, the fishery reacted as expected and reached its objective in terms of reconstruction of the biomass, but the overall assessment in terms of resulting profitability is not very conclusive. There is no evidence of decrease of the profitability over the period of the study but the fishery is more reactive to external factors on its export market in China than to changes in its own structure.

Chez deux espèces de crevettes pénéides, Penaeus japonicus et P. chinensis, les conditions de survie en fonction de la température et de la salinité ont été déterminées sur les post-larves P20, P40 et P60. Les SL50, 96 heures moyennes pour les trois stades sont respectivement de 19,3 ‰ à 10 °C, 12,1 ‰ à 14 °C, 6,4 ‰ à 18 °C et 5,4 ‰ à 25 °C pour P. japonicus et de 11,3 ‰ à 14 °C, 7,2 ‰ à 18 °C et 11,1 ‰ à 25 °C pour P. chinensis. L'abaissement de la température de 18-25 °C à 10-14 °C diminue fortement la tolérance des post-larves de P. japonicus aux faibles salinités alors que pour P. chinensis ce phénomène est beaucoup moins marqué. Quelle que soit la température, la mortalité est minimum dans les milieux à peu près isosmotiques à l'hémolymphe. Des essais de survie à long terme (35 jours) ont été effectués sur les post-larves des deux espèces. La régulation osmotique des post-larves et des adultes des deux espèces est hyper-osmotique en milieu dilué et hypo-osmotique en eau de mer et 900 mosm.kg−1. Chez P. japonicus il n'y a pas de différence significative entre les courbes de régulation osmotique des P20, P40 et P60 en milieu dilué. Par contre les capacités osmorégulatrices des adultes sont inférieures à celles des post-larves. Chez P. chinensis l'intensité de la régulation en milieu dilué augmente avec l'âge des post-larves et les adultes présentent une capacité hyper-régulatrice supérieure à celle des P60. L'étude de l'action de la température sur l'osmorégulation des P40 de P. japonicus a montré que l'abaissement de la température de 18 à 10 °C pendant 8 jours modifie fortement la régulation qui devient isosmotique en eau de mer. Les différents résultats obtenus permettent de définir les conditions optimales de température et de salinité pour les élevages de post-larves et les ensemencements en bassins ou lagunes.

Over a 3-year period at the Sukamandi station (West Java, Indonesia), 107 Pangasius hypophthalmus females were selected on the basis of a modal oocyte diameter greater than 1.0 mm and treated with either Ovaprim (n = 97) or hCG (n = 10) to induce oocyte maturation and ovulation. The two hormonal treatments led to similar results in terms of ovulation rate (88 and 90 %), hatching rate (72 ± 25 and 82 ± 11 %) and relative fecundity (171000 ± 73000 and 128000 ± 60000 ova·kg–1, with Ovaprim and hCG, respectively). The latency period between the last hormone injection and ovulation was negatively correlated to water temperature but showed important variations at a same temperature depending on individual females (e.g. between 5 and 11 h at 28–29 °C). The ovulation time was therefore difficult to predict accurately in this species. The assessment of the viability of ova retained in the ovarian cavity after ovulation showed that the process of overripening occurs rapidly in P. hypophthalmus. The overall quality of ova began to decline as early as 2 h after ovulation and, after 3 h, hatching rates decreased and the proportion of deformed larvae increased significantly in comparison to those observed at the time of ovulation. In some individual females this process occurred even more rapidly, with a sharp decrease in hatching rates between 1 and 2 h post-ovulation. The duration of ova survival did not appear to depend on the type of hormone treatment used to induce ovulation (Ovaprim or hCG). For optimized gamete management in hatcheries, it is therefore recommended to check carefully the females for the occurrence of ovulation (between 3 and 11 h after the last hormone injection, depending on water temperature) and to strip and fertilize the eggs less than 2 h thereafter.

Juvenile pelagic fishes are integral members of many coastal river communities. Many of these systems are boldly influenced by variable wind stress and freshwater inputs that can increase heterogeneity in estuarine habitat for fishes. We use mobile sonar surveys within the Neuse River Estuary System, NC, USA to assess the distribution and behavioral patterns of juvenile anchovies, Anchoa spp. 25-65 mm TL, over a broad range of spatial scales in relation to diel and seasonal changes in water quality including stratification, hypoxic events and copepod distribution. Results from our study indicate that episodic stratification-induced hypoxic events can reduce suitable habitat volume for anchovies by more than 50%. Furthermore, our sampling suggests that hypoxia causes spatial separation between plankton and the grazing fishes. Under stratified oxygen conditions, we observe higher densities of copepods in hypoxic bottom water. Finally, we report that reductions in available habitat caused an increase in local densities of fishes and may result in increased competition for resources. These spatially explicit data are critical for developing trophic dynamic models that predict the response of fish communities to natural and anthropogenic impacts on the system.

Restoration of shellfish populations is becoming an increasingly common practice worldwide, as natural fisheries succumb to pressures of overharvesting, habitat loss or degradation, and challenges from invasive competitors and pathogens. Primary genetic concerns relevant to shellfish restoration projects are reviewed, using the cupped oysters Crassostrea gigas and Crassostrea virginica as case studies. Molecular genetic tools can be used to delineate the geographic distribution of germ plasm diversity at the species and intraspecific levels, enabling more informed selection of genetic material for hatchery breeding and production. Maintenance of genetic variability and prevention of excessive inbreeding in hatchery stocks may be facilitated by the use of genetic markers for regular pedigree monitoring. The effect of hatchery supplementation on the effective population size of a recipient wild population (Ryman-Laikre effect) is reviewed in light of the population biology of bivalve molluscs, and appears to be minimal. Deployment of selected enhancement stocks may be a valuable tool for improvement of degraded wild populations, reversing the negative effects of generations of selective harvesting. Molecular genetic tools can be used effectively to monitor restoration programs, when the discriminatory power of the marker(s) is high and high-throughput scoring methods currently available are used.

A study of the growth and mortality of the European oyster Ostrea edulis, including the effects of Marteilia refringens and Bonamia ostreae, was carried out in three oceanic areas in the Bay of Areachon from May 1989 to February 1991. One-year-old spat, free from discase were used for the trials. Six months after beginning the trials, Marteilia refringens had severely infested the cultures. Although Bonamia ostreae was found during the first year, the rate of infestation was low. In the second year Bonamiasis increased and high mortality (>60%) occurred in Ostrea edulis populations. Although the growth of the oysters was good, their condition index was generally poor. Moreover, shell perforations by Polydora sp. were observed. In spring 1990, a low glycogen storage was notedwhich may have been related to the Marteilia refringens infestation although no relationship with the carbohydrate content and mortality was detected. The influence of different rearing procedures on Ostrea edulis survival and development in four commercial batches of oysters, free of discase, was also studied. The growth of Ostrea edulis in single culture was better than in cultures mixed with Crassostrea gigas. However, infestation by Marteilia refringens and Bonamia ostreae in the laid cultures was quite similar to that of the experimental cultures (bags). Due to the persistence of these two parasites, the culture of Ostrea edulis on a commercial scale is not advisable in the Bay of Arcachon.

The Argentine shortfin squid (Illex argentinus) is a common neritic species occurring in waters off Brazil, Uruguay, Argentina, and the Falkland/Malvinas Islands in the southwest Atlantic. Illex argentinus is the most important fished cephalopod species in the area and plays a significant role in the ecosystem. It is object of major fisheries using both trawlers (mostly from European countries) and jigging vessels (mainly from Asian countries) and estimated total annual average catch for the last 15 years (1988-2003) is about 700 000 tons. The present paper aims to develop predictive models of squid abundance in relation to physical and environmental conditions, models that could ultimately be applied to fishery forecasting. Fishery and biological data collected by scientific observers aboard commercial trawlers between 1988 and 2003 were analysed in relation to physical and environmental factors to establish the spatio-temporal pattern of the species' distribution and quantify the influence of environmental variables (e.g. SST, depth) on local abundance. The data included 26 168 fishing haul records, of which 11 103 were positive for Illex. CPUE (Catch Per Unit Effort, kg h−1) was used as abundance index. The analyses were based on time-series maps created using Geographical Information Systems (GIS). GIS maps showed that highest CPUE values were recorded during the first four months of the year (the Austral summer-autumn), with peak values higher than 5000 kg h−1 mainly located within 42° S, 46° S and MN (North part of Malvinas/Falkland) areas. Generalised additive models (GAMs) were used to describe variation in Illex argentinus abundance in relation to geographical and environmental variables. The presence/absence (PA) of Illex and its abundance (CPUE) in areas of presence were modelled separately. Predictors retained in the optimal models included SST, latitude, longitude, month, average fishing depth and year. Both models suggest a clear seasonal effect: maximum catchability was found during March (PA model) and the maximum abundances were found during the first quarter of the year (CPUE model). GAM models also demonstrated that higher catches and maturity of squid were related, in general terms, to warmer and deeper water.

An investigation was carried out during the Illex argentinus trawl fishery (January-July) in the fishery regions of 42 °S and 45-47 °S off the Exclusive Economic Zone of Argentina between 1985 and 1990. Statoliths of 5,232 squid were sampled and processed to study age and growth patterns in squid, hatched in different months. Among squid of similar ages (within an age interval from 180 to 300 days), the May-hatched squid were the smallest while the September-hatched were largest. Growth rates of squid of the same hatching-months were significantly different according to year, but these differences were considerably smaller than those observed between various hatching-months within one year. The largest individuals at a given age were captured in 1990, and the smallest in 1985. Males and females became mature at age 220-320 and 210-360 days respectively. The maturation period lasts 1.5-2.5 months in males and 1 month in females. Early and late-maturing groups were observed within each hatching-month. The peak. of spawning was in July of 1984, 1986, 1987, in June of 1985 and in August of 1989.

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.

West African marine ecosystems are very productive and sustain important fisheries that have developed rapidly in the last decades. The analysis of the fishing impact on exploited resources is usually conducted through single-species assessments. In this study, we propose a complementary approach that enables to account for some ecosystem effects of fishing. In Guinea and Senegal, fisheries have developed relatively recently and at the same time, the collection of landings and surveys data has been carried out. In consequence, the data collection extends from a period where stocks could be considered as non exploited to a situation of overexploitation. This case study is analysed in order to detect shifts in the ecosystem structure in response to increasing fishing pressure. To this aim, trophic spectra and long time series of mean trophic level are examined for demersal fish communities. Trophic spectra display either the distribution of the demersal community biomass or the commercial catches according to trophic level classes. Some substantial and statistically significant changes in the trophic structure of the Senegal and Guinea ecosystems were observed. In particular, the biomass of the high trophic levels decreased whereas the lower trophic levels displayed a relative stability or an increase. This could be linked to a “top-down” fishing effect due to a release of predation on the lower trophic levels of the demersal fish community. In Senegal, the mean trophic level decreased significantly for both the catches and the demersal community biomass. Such a decrease was also observed for the coastal demersal biomass in Guinea. This showed that fishing activities had an impact on the trophic structure of the ecosystem, and a “fishing down marine food web” effect was shown in West Africa for the first time.

Coral reefs in French Polynesia, just like many others throughout the world, have been subjected to several natural disturbances including 15 cyclones, seven major bleaching events, and several Acanthaster planci outbreaks since the 1980s. In order to document the effects of these perturbations on coral assemblages, we initiated a long-term monitoring program that extended over both local and regional scales. Coral cover was quantified at 20 sites situated on the outer reef slope of 13 islands. The results from the first decade (1992-2002) are analyzed and the adequacy of our approach is discussed in the context of identifying potential indicators of coral reef health. Among 13 islands in French Polynesia, only two were unaffected by natural disturbances. We found important local and regional variation in the impacts of coral bleaching and cyclones, and three major temporal trends were distinguished: 1) 10 sites where coral cover decreased in relation to the occurrence of major disturbances; 2) nine sites where coral cover increased, despite the occurrence of disturbances affecting seven of them; and 3) a site where no significant variation in coral cover was found. The responses to perturbations were different among coral genera: Acropora species were particularly susceptible to bleaching events, whereas physical damages induced by cyclones concerned mainly branching species of Acropora and Pocillopora. Thus, monitoring surveys could be improved by selecting different and complementary indicators (one on the variation in diversity, one estimating changes in the abundance/cover, and one estimating the potential for recovery), by integrating several spatial scales, and by including at least the most informative species. High frequency recordings of environmental parameters (e.g. sea surface temperature) may be also a complementary tools for identifying causal relationships between changes in coral reef community structure and the factors causing the changes.