The rapid development of the albacore tuna (Thunnus alalunga) driftnet fishery in the Bay of Biscay (Atlantic ocean, France) has incited European management authorities to ask for a study of its ecological impact on populations of common dolphins and striped dolphins. A programme with onboard observers has been led during 1992 and 1993, and a sighting survey has allowed the evaluation of the abundances of fractions of populations in the studied area. For the population of common dolphins, the biological parameter estimation has allowed the building of a discrete age-structured model based on a Leslie matrix. Sensitivity studies have been conducted using four model parameters (age of first reproduction, interval between births, juvenile and adult survival rates. Results show that the increase rate of the population presents the highest sensitivity versus adult survival rate and, in second place versus the interval between births.

The commercial culture of several important species of fish has long been associated with productivity problems generally attributable to fertilisation rates, hatching rates, and embryonic development. Our present knowledge of the molecular processes accompanying fertilisation in fish is scant at best. Here, we examine how new findings about the molecular mechanisms underlying reproduction in other animal groups may help advance our understanding of how egg activation takes place in fish. A better understanding of egg activation in fish is likely to make a highly valuable contribution to future growth of the aquaculture industry.

In the Java sea, pelagic fish are exploited by purse seiners. The resource is dispersed and has to be aggregated before being fished. Light is used to reach this objective. The purse seiners are mobile and fish in ‘packs’. When concentrations of fish are found the fishing vessels gather in clusters. The spatial characterization of these clusters provides better understanding of the fishing strategy followed by the purse seiners. A point process approach is used to understand the clustering process and determine the life time of the clusters. The calculation of a density function defines the surface influenced by the cluster and estimates the intensity of the exploitation inside it. Clustering is the mark of the fishing phase that is defined by the significant divergence of the L-function from the Poisson process. In the fishery, such a result is observed when at least 15 purse seiners are gathered. Usually, the fishing phase lasts 4–6 days. The surface covered by the clusters represents a small part (15–25 %) of the surface that is accessible to the fleet. In these areas, the fishing intensity can reach high values (160 vessels × nautical mile–2).

Les teneurs en mercure de plusieurs espèces de poissons sont expliquées en utilisant un modèle présenté antérieurement par Thomann (1981), basé sur le transport des contaminants en milieu marin et leur transfert à travers les chaînes alimentaires aquatiques. Il est montré en particulier que les facteurs environnementaux liés au processus de méthylation du mercure qui se déroule dans la colonne d'eau et à la surface des sédiments, peuvent être responsables des teneurs particulièrement élevées decertaines espèces. Notre interprétation originale de teneurs en mercure de nombreuses espèces de poissons de l'Atlantique pêchés entre 1971 et 1980, est accompagnée de la présentation de "concentrations de référence" qui peuvent être d'utilité pour établir des comparaisons avec d'autres valeurs comme par exemple les teneurs d'autres poissons capturés à une autre époque ou dans d'autres régions.

A preliminary economic evaluation of the feasibility of establishing a fishery to process red crab meal (Pleuroncodes planipes) was conducted. Risk assessment indicated that a fishery of nine boats could operate with an average 1.53 benefit-cost ratio (B C−1) and annual net revenues (NR) of US$427 840, and that there is certainty of obtaining economic profit in every season, with a B C−1 > 1 and NR > 0. Total catch and average catch per trip could be reduced from a total baseline catch of 10 328 tons (1735 t meal) to 6061 (1844 t meal), and from a baseline catch per trip of 11.4 t (4.78 t meal) to 6.73 tons (4.85 t meal) without economic losses. There was no possibility for profit when total catch and average catch per trip were, respectively, lower than 5365 t (1648 t meal) and 5.96 t (4.71 t meal). For a single-fishing trip operation, average B C−1 was 1.5 and NR was US$480. We determined that there was a confidence level of 84% to generate profits. To guarantee profits, a catch of 13.5 t per trip (1.35 t meal) should be obtained. Single trips catching less than 3.3 t (0.94 t meal) cannot make a profit. Sensitivity analysis indicated that plant processing efficiency for converting fresh red crab to meal, catch per trip, and sales price of red crab meal were most important in determining B C−1 and NR values. Plant efficiency constitutes the main element that needs to be optimized, particularly management practices to preserve fresh catch quality. A low sensitivity to costs for processing suggests the possibility of negotiating a higher price and the opportunity for processing plants to venture into processing of red crab meal.

This is the first report of early-life developmental characteristics (coloration pattern, growth and survival) and genetic identification of the wolffish interspecific hybrid between Anarhichas minor and A. lupus, both endangered species in Canadian coastal water and of interest for cold-water aquaculture diversification. A first growth trial at 8 °C featuring pure strains A. minor and the hybrid A. minor × A. lupus in triplicates was conducted in 2006 during the period from 0 to 140 days post-hatch. A second growth trial was runned in 2007 featuring A. minor, A. lupus and the reciprocal hybrids A. minor × A. lupus and A. lupus × A. minor. Egg development indicators and early-hatching characteristics are reported.

This work is aimed at demonstrating the influence of insulin in the triggering of hepatic cholestasis in young gilt-head sea bream larvae reared under experimental conditions. The results are based on an immunological assay of insulin and an ultrastructural study of the yolk syncytial layer and the liver. Compared to fed larvae, fasting gilt-head sea bream larvae displayed a substantial increase in insulin level correlated with dysfunction of the yolk syncytial layer and hepatic histopathology. This correlation was verified in larvae reared in sea water containing insulin. Ultrastructural observations suggested that insulin affects lipoprotein secretion by the yolk syncytial layer. The failure of plasmatic lipoproteins would then cause dysfunction of the biliary lipid secretion mechanisms and, hence, trigger hepatic cholestasis. These results in gilt-head sea bream show for the first time the influence of insulin in the triggering of hepatic cholestasis during the early development of a vertebrate.

Les poulamons de la rivière Sainte-Anne frayent dans un secteur de rapides, situé à environ 7 km de la confluence avec le fleuve Saint-Laurent, et probablement aussi dans un secteur d'accumulation de frasil généré par ces rapides. Les variations interannuelles dans la dérive des œufs et des larves de poulamon, à différentes stations dans la rivière, sont reliées aux conditions annuelles de température de l'air et de débit. Des températures et débits bas et stables ont causé la rétention des œufs et des larves dans la partie amont du secteur d'étude (1980–1981, 1981–1982); les températures et débits plus élevés et variables ont causé une dérive régulière au fleuve Saint-Laurent de janvier à avril (1982–1983). En 1980–1981, une hausse soudaine de la température et du débit a causé une avalaison massive des œufs au Saint-Laurent durant la seconde moitié de février. Des œufs de poulamon sont retenus et incubés dans le frasil, qui s'accumule en un barrage suspendu pouvant s'étendre, selon les années, sur plus de 3 km de rivière. Peu de temps après la fraye, la densité moyenne d'œufs par 2 l de ce substrat, sur l'ensemble du barrage suspendu, atteignait 228 en 1981 (19 janvier), 235 en 1982 (6 février), et 54 en 1983 (15 février). Les variations interannuelles dans la distribution spatiotemporelle des œufs dans le frasil concordent avec celles suggérées par les résultats de la dérive.

L'étude présente une application de la méthode géostatistique transitive à une dimension (1D) pour estimer la précision des évaluations de biomasse effectuées au Sénégal par écho-intégration. Le problème majeur rencontré dans cette étude a été la prise en compte de la variabilité temporelle dans l'estimation de la variance d'échantillonnage. Lors des campagnes acoustiques, l'écho-intégration se fait en continu le long de la route du navire. Lorsque le plan d'échantillonnage est constitué de transects parallèles, cette caractéristique permet de considérer chaque transect comme une unité d'échantillonnage. En faisant la somme des valeurs mesurées le long des transects, l'estimation à 2D est simplement ramenée à une estimation à 1D. Si de plus les transects sont équidistants, la méthode géostatistique transitive à 1D offre une solution correcte et simple au calcul de la variance d'estimation. La méthode a été appliquée à la série des campagnes acoustiques sénégalaises qui ont toutes été effectuées selon le même réseau de transects équidistants et parallèles d'orientation Est-Ouest. Les densités sont sommées le long des transects. Les variations latitudinales de la biomasse par transect sont présentées sous forme de profils à 1D. La biomasse, la répartition spatiale et l'autocorrélation sur ces profils présentent des différences importantes d'une campagne à l'autre. Les profils ont été regroupés en 4 catégories présentant des caractéristiques différentes. L'autocorrélation moyenne (structure) par catégorie a été estimée et modélisée. Une valeur moyenne de l'erreur relative d'estimation est fournie pour chaque catégorie. L'erreur relative d'estimation varie en fonction des différences de structures entre catégories et aussi en fonction de différentes hypothèses pour la modélisation de la structure aux petites distances. Deux cas ont été considérés : continuité de la distribution (absence d'un effet pépite) ou discontinuité (présence d'un effet pépite). L'erreur relative maximale estimée est d'environ 31 %. Le problème majeur rencontré à la modélisation de la structure 1D des biomasses par transect a été de choisir de prendre en compte ou non un effet de pépite. L'interprétation de cette pépite serait la variabilité temporelle à l'échelle de la radiale.

An indirect fluorescent antibody test (IFAT) incorporating a polyclonal antibody to Marteilia sydneyi recognized spornlating stages of M. sydneyi from Saccostrea commercialis but not those of Marteilia refringens, M. maurini, Marteilia sp. and Marteilioides branchialis from Ostrea edulis, Mytilus galloprovincialis, Mytilus edulis and Saccostrea commercialis respectively. This indicates that the antibody had a high specificity and that the other parasites were immunologically distinct from M. sydneyi. Immunoelectron microscopy was used to investigate background labelling and the specificity of the antibody to antigenic sites. It showed that though most immunoglobulins were specific to parasite epitopes, some reacted to host tissue. IFAT's based on three monoclonal antibodies raised against Marteilia sp. did not recognise sporesor other stages of M. sydneyi. An immunogold-silver staining technique using the polyclonal antibody to M. sydneyi failed to identify the presumed presporulation stage of M. sydneyi in the connective tissue of a recently infected host. This suggests the antigens were stage-specific. Thus a DNA probe rather than immunohistochemical tests may be more useful in investigating the life cycle of this parasite.

The toxicity of sewage sludge to adult and larval Sand shrimp, Crangon crangon, and larval brine shrimp Artemia salina, was studied. Temporal changes in toxicity, ammonia and pH of sewage sludge in seawater were determined. The feasibility of sediment choice bioassays using adult Crangon were examined. The 24 h LC50 of sewage sludge at 20 °C was 0.4% sludge for Crangon larvae, and 10.0% for Artemia larvae. Toxicity to Crangon larvae decreased with decreasing ammonia and increasing pH as sludge decayed over 7 days. In adult Crangon, a dose response with greater variation at < 3% sewage sludge (wet volume in seawater) was found. For adult Crangon at 10 °C, the LT50 at 1% sludge was 80-90 h and 96 h LC50 0.8-1.7% sludge. No clear differences were apparent between 96 h LC5O's in static and 24 h renewal tests. Adult Crangon avoided sediments mixed to concentrations of 6.25% and 10% sewage sludge, but buried at similar frequencies in uncontaminated and 1.57% sludge sediments. In addition to possible chemical effects from ammonia and other sewage sludge components (e.g. metals, organochlorines, hydrocarbons), sludge solids may have physical effects on Crustacea. Bioaccumulation is possible if persistent contaminants occur in the sludge. From estimated field concentrations of sewage sludge, and the results of this and other toxicity studies, lethal effects at sewage sludge disposal sites are believed unlikely. However, further sediment studies (longer-term, life-cycle, bioaccumulation, and mesocosm) are required to evaluate the role of sediment tests in understanding the effects of sewage sludge on benthic Crustacea.

Atlantic salmon, Salmo salar, and several species of whitefish, Coregonus nasus, C. peled, C. Lavaretus baeri, males were treated with a long-acting medical androgen preparation - "Testoenatum". This preparation contains 24 mg of testosterone enanthate and 111 mg of testosterone propionate in 1 ml peach oil solution. Multiple (2–5) or single intraperitoneal injections of a standard dose (0.1 ml/kg fish body weight) were used. Treatment performed shortly before the beginning or within the breeding season resulted in a significant stimulation of spermiation, improvement of sperm parameters and extention of the gonad functional maturity period for 1–4 months. Low water temperatures (0.5–l.0 °C) seem to be essential to obtain a long-lasting effect after one injection. The histology of the pituitary gland suggests that the gonadotropic cells were activated through a positive feedback mechanism. Testoenatum suppressed Sertoli cells' phagocytary activity.

Depuis 1988, d'importantes mortalités de palourdes japonaises Ruditapes philippinarum ont été enregistrées, sur de nombreux élevages, dans le bassin d'Arcachon. Pour expliquer celles-ci, l'hypothèse d'une prédation par la dorade royale Sparus aurata et par le baliste Balistes capriscus était avancée. Afin de la vérifier, une étude expérimentale de la prédation de la palourde par ces deux poissons a été réalisée en laboratoire. Si les relations taille prédateurs-taille proies sont plus marquées chez le baliste, les deux espèces sont particuliérement voraces, puisqu'elles s'avéraient capables de consommer, en 24 h, 500 petits naissains et 350 jeunes palourdes de 25 mm de longueur, 50 % à 70 % des proies étant consommés au cours des 6 premières heures. L'observation de la cassure de la palourde, identiquechez les deux espèces, (menues brisures de coquilles) et des traces laissées sur le sédiment par ces prédateurs, ne peuvent être retenues comme critères distinctifs. Le comportement alimentaire de ces poissons est fortement influencé par la température. Ainsi à 16 °C, une prédation de très faible intensité est observée. Seule la pose d'un filet tendu sur le sol ou légèrement surélevé s'avère être actuellement la seule parade efficace pour lutter contre ces prédateurs. Les mortalités, enregistrées sur de nombreux parcs vénéricoles du bassin d'Arcachon, en période estivale, sont, en partie, imputables à une prédation par la dorade et le baliste. Bien que l'échelle de prédation soit plus étendue chez la dorade. l'action du baliste sur les élevages de palourdes est particulièrement préoccupante car cette espèce est extrêmement résistante et inexploitée.

In many atolls of the South Pacific, a shift has occurred in the past couple of decades from traditional to more intensive fishing practices. Increasing fishing pressure on coral reefs raises the need for long-term studies to understand how fish communities react to fishing practice changes. The objective of this study was to analyse the variations of reef fish communities (in terms of species richness, diversity, density and structure) during a long time lapse at Tikehau atoll (Tuamotu archipelago, French Polynesia). The same eight lagoon pinnacles were sampled in 1987 and 2003 at 6 and 12 m depth. Quantitative data were collected by visual census techniques (UVC) on 50 m × 5 m belt transects. Analyses were conducted using a multiple spatial scale (depth, pinnacle and whole lagoon) approach with a particular attention on commercial species such as Scaridae (parrotfish), Acanthuridae (surgeonfish), Lutjanidae (snapper), Lethrinidae (emperor), Serranidae (grouper). Despite an increased sampling effort between 1987 and 2003, the mean species richness per transect decreased significantly from 26.2 ± 6.2 to 21.6 ± 9.6. The mean diversity varied similarly. A stronger decrease happened at pinnacles close to the village, where fish density also decreased. Conversely, fish density, species richness and diversity increased at pinnacles less visited by inhabitants. The community structure shifted from commercial species to small site-attached species e.g. Pomacentridae (damselfish), Ptereleotridae (dartfish) as fishing reduced the abundance (and biomass) of targeted stocks. We argue that these spatiotemporal variations resulted from a drastic change in fishing practices over the 16 years period, that shifted a sustainable fishery using traditional fish traps to an unbalanced, species-threatening, selective fishery. This study underlines the need for management and for the implementation of marine protected areas (including no-take zones) in order to protect the coral reef ecosystem and favor sustainable fisheries at Tikehau atoll.

Emphasis on physiological adaptations to environmental changes in the catfish (Siluroidei), is a rather recent development like that of their use in aquaculture. The siluroid fishes with smooth scaleless skin and sensory barbels are adapted to live in a variety of aquatic environments ranging from freshwater and brackishwater to swamps and marshes both in temperate and tropical regions. However, very little has been explored on their expected wide range of physiological adaptations. Most of the results obtained in siluroid fishes are similar to those reported for other teleosts such as cypriniform species. However, there are some air-breathing siluroids, found in the tropical areas, with accessory air-breathing organs. Besides tolerating periods of water deprivation, some of these fishes have been shown to possess-special physiological and biochemical adaptive mechanisms to tolerate a wide range of adverse physico-chemical conditions in the ambient environment. Some of the physiological adaptive mechanisms of Siluroidei in general, and air-breathing species in particular, to important physico-chemical factors such as oxygen,temperature, ammonia and xenobiotics are reviewed and discussed.

Marine fisheries and the ecosystems that sustain them are increasingly beset by environmental deterioration, and the problem is particularly acute in coastal zones where human populations are increasing. In the best of circumstances, fishery managers are faced with the multiple, often conflicting, demands of resource users, politicians, and scientists when considering strategies for resource management. A further challenge is that management decisions must be made against a backdrop of a deteriorating environment and the shifting status of coastal ecosystem integrity. Traditional tools for single-species management may be inadequate in these settings. Furthermore, the necessary empirical data to appropriately parameterize models with vital rates representative of an altered environment are often lacking. Thus, we need approaches that better approximate the complicated dynamics between environmental conditions, fishery impacts, and multi-species interactions. Spatially-explicit, individual-based simulation modeling potentially permits this kind of integration, but it has seen limited use in marine resource management, especially with respect to benthic resources. My colleagues and I have used this approach, combined with targeted experimental work, to explore the impacts of nursery habitat deterioration, coastal freshwater management, and fishery activities on Caribbean spiny lobster populations and sponge community structure in the Florida Keys, Florida (USA). Although not applicable for all resource management situations, our experiences provide an example of the potential use of spatially-explicit, individual-based modeling and targeted empirical science in predicting resource conditions in a dynamic environment.

Deux expériences ont été réalisées pour tester la valeur alimentaire, pour le mâchoiron (Chrysichthys nigrodigitatus), de dérivés de poissons de mer conservés par la méthode de l'ensilage. Le premier essai a concerné des déchets de conserveries de thons conservés par la méthode de l'ensilage acide (3 % d'acide formique). L'hydrolysat, renfermant 66,7 % de protéines brutes (N × 6,25) sur la base de la matière sèche (MS) a été incorporé dans un aliment expérimental en substitution à la farine de poisson sur une base iso-azotée. Les aliments ont été distribués à 6 lots de 50 mâchoirons, d'un poids initial de 34 g, pendant 56 jours à raison de 3 % (sec) du poids vif. Les performances zootechniques procurées par cet aliment sont meilleures, pour ce qui concerne le gain de poids (0,86 g.j−1) et l'indice de consommation (IC : 1,79) et le coefficient d'efficacité protéique (CEP: 1,46), par rapport à celles obtenues avec l'aliment témoin (pas de différence significative). Lors du deuxième essai il a été réalisé un complexe hydrocarboné à base de maïs pour conserver des sardinelles broyées par fermentation lactique. Ce mélange (coensilage), à pH stabilisé à 4,18, et renfermant 35,65 %, de protéines brutes (N × 6,25) en matière sèche (MS), a également été testé contre un témoin farine de poisson dans des conditions expérimentales identiques à celles décrites plus haut. L'aliment à base de coensilage a procuré de meilleurs gains, de poids (0,94 g.j−1, IC (1,77) et CEP (1,61) que l'aliment témoin. Les produits de la pêche ou leurs dérivés conservés par la méthode de l'ensilage acide ou du coensilage biologique apparaissent ainsi constituer une bonne source azotée pour l'alimentation du mâchoiron.

Blue mussels (Mytilus edulis) and soft-shell clams (Myaarenaria) are both aquaculture species in east coast of Canada and US shellfishfarmers take advantage of the byssal threads production of mussels for suspension cultureand the burrowing behaviour of soft-shell clams for enhancement practices. It is importantthat these animals attach and burrow efficiently to minimize losses during rearing. Theaim of this work was to study two potential vitality indices on mussels (23.6 ± 0.1 mm) and clams (22.6 ± 0.1 mm) seeds following variousperiods of emersion: attachment strength of Mytilus edulis and burrowingability of Mya arenaria. The effect of emersion on energy content(proteins, lipids, glycogen) was also examined. We observed no significant decrease in theattachment strength of mussels after air exposure for 78 h or in the burrowing efficiencyof soft-shell clams after 54 h. Air exposure had no effect on different lipid classes,proteins, or glycogen content in either mussel or clam tissues. The stressful emersionevent induced in our study may not have been high enough to induce detectable behaviouralresponses. This can be explained by the bivalves’ ability to adapt their metabolism tominimize activity during air exposure. In doing so, they do not consume their energyreserves, which are then still available when specimens are reimmersed. Thus mussels areable to efficiently produce byssal threads and clams to burrow into sediments as soon asthey are back in the water.