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.

L'histologie des gonades de 187 mâles et 149 femelles de Myleus ternetzi pêchés dans des rivières guyanaises a été étudiée. Les stades et le cycle de la spermatogenèse ont été analysés à l'aide d'une méthode téréologique. L'ovogenèse a été étudiée et le stade de maturation de chaque femelle déterminé. La vitellogenèse est discontinue et au moins trois pontes pourraient avoir lieu lors de la saison de reproduction. La fécondité relative est d'environ 10 000 ovocytes par kilogramme par ponte. Bien que aptes à se reproduire toute l'année, la plupart des Myleus ternetzi se reproduiraient juste avant la grande saison des pluies.

This study investigates whether pelagic fish schools of different species or groupings (e.g. herring, "surface herring", "gadoids", mackerel, sprat and sandeels) were positively or negatively associated with each other in time and space. To do this, statistical models were fitted to pre-processed acoustic fisheries data to reveal how pelagic school prevalence varied with respect to spatial (latitude and longitude) and temporal (time of day) information. The model outputs, which take the form of probabilities fitted to the presence or absence of schools, were then used to calculate correlation coefficients, which are useful for measuring association between pairs of variables. Results depended upon the specific species pairs under investigation. Herring and "surface herring" were, for example, very generally sympatrically associated with each other in both space and time, while herring and gadoid schools, on the other hand, had allopatric distributions.

La répartition spatiale des nasses à poisson et à langoustes sur le plateau sud-est de la Martinique est étudiée au moyen d'observations en mer et de données bathymétriques. A l'intérieur du récif-barrière, l'essentiel de l'effort est déployé le long de la ligne de tombants qui borde la côte ; à l'extérieur du récif, la répartition individuelle des nasses est pratiquement indépendante du relief sous-marin, mais il existe une forte corrélation entre les moyennes d'effort et d'indice de relief par tranches bathymétriques de 5 m. La relation seulement indirecte entre effort de pêche et relief du fond à l'extérieur du récif semble être le résultat de conditions d'exploitation difficiles (éloignement de la côte, état de la mer) mais aussi de choix délibérés des pêcheurs. Ces résultats conduisent à discuter la notion de « surface exploitée » utilisée pour calculer des captures ou des efforts par unité de surface. L'utilisation de surfaces corrigées à l'aide des indices de relief conduit à une image plus réaliste de la répartition de la pression de pêche sur le plateau insulaire de Martinique.

The transfer of polycyclic aromatic hydrocarbons (PAHs) from bivalves, through the food chain to vertebrates was of concern. Our research aimed at estimating potential effects for consumers resulting from the ingestion of seafood contaminated by oil spill pollutants.After the “Erika” wreck, mussels (Mytilus sp.) were collected from sites of the Atlantic coast impacted to various degrees by the oil slick and constituted contaminated food for rats during 2 and 4 weeks. Genotoxic damage were studied in rats by means of COMET assay carried out in liver, bone marrow and peripheral blood. Biochemical and genomic effects such as the induction of CYP 1A1 and the expression of cytochrome genes were measured in rat livers. The most sensitive biological parameter reflecting the transfer of contaminants via the food appeared to be DNA breaks studied by means of the COMET assay. Genotoxic damage, observed mainly in the liver, were rather moderate and remained not persistent. This study underlined the bioavailability of pollutants in fuel oil contaminated mussels for consumers, and the complexity of the contamination consecutive to the oil spill. The occurrence of related PAH compounds in addition to non-substituted PAHs in fuel oils and mussels raised the question of their implication in the registered effects.

The black bullhead, Ameiurus melas of the family Ictaluridae, is a freshwater fish native to North America that was introduced throughout Europe in the late 1800s. Using mitochondrial DNA (mtDNA) as a genetic marker, the present study investigates the genetic structure and historical demography of A. melas in North America. MtDNA-based phylogenetic analyses revealed the existence of two distinct lineages (A and B) of A. melas. While lineage A clustered with the previously reported sequences of A. melas, lineage B emerged as a unique clade like other species of the genus Ameiurus. Individuals belonging to lineage B were mostly from the south central region of the United States, the region that never glaciated during the last Ice Age. Results of a fossil-based molecular clock analysis suggest that lineage A and the paraphyletic lineage B of A. melas diverged from their respective common ancestors approximately 3 (±0.2) and 15.9 (±1.3) million years ago. Lineage B could possibly be a hybrid species, possessing the mtDNA haplotype of its maternal parent, an Ameiurus species that has gone extinct. While lineage A showed evidence of population expansion, lineage B did not show any evidence of population expansion, but rather is comprised of geographically structured populations.

Acoustic surveys for determining fish abundance in shallow water present many challenges. One constraint to down-looking (or vertical) surveys is that the sampling volume is limited due to the short range and typically narrow beams of acoustic transducers. By utilizing more of the acoustic beam, into the side-lobes for example, the sampling volume may be increased. Although the echo energy contribution from the side-lobes is usually small, these echoes may influence target strength estimation and echo counting, and by extension affect abundance estimation either directly or indirectly. With the advent of wide dynamic range echosounders, it is possible to assess both small and large acoustic-size targets. In this case, it is possible to collect signals from large targets in the beam side-lobes, and therefore an algorithm to use side-lobe data is proposed. The smoothed Expectation Maximization method (EMS) is used to estimate densities and target strength of fish from only main-lobe and main-lobe with side-lobe observations in simulation, and suggestions are made for real data from surveys.

The swimming, air-gaping, and agonistic behaviours of Heterobranchus longifilis (318 ± 67 mm) were examined while fish were in a fasted state under 12L:12D and variable group size (2, 5, 10 and 15 fish) in a 1000-L aquarium. Fish exhibited a predominantly nocturnal activity pattern independent of group size. A diurnal peak of activity occurred, however, at the usual feeding time. A reduction in frequency of agonistic interactions was observed in larger groups. Five fish were then observed under 72L:0D and 0L:72D. The nocturnal activity pattern remained, contrary to the diurnal peak, and was independent of the duration of illumination or darkness. These results suggest the absence of biological clock in H. longifilis, although fish may somehow be influenced by past feeding experience. Behavioural plasticity in this species may provide potential for aquaculture in northern latitudes.

Pinctada margaritifera mollusc is cultivated in French Polynesia for the production of black pearls. For this study, the colour of juvenile samples (48 days old) was investigated in the visible range spectra (430–700 nm) using spectrophotometry. A first measurement was done with the soft parts still inside the shell (entire animal). Then, the soft parts were removed in order to do a second measurement on the growing edge of the shell. Comparison of the two measurements shows that the estimation of the living animal colour with unaided eye is strongly influenced by the colour of the soft parts. The use of the International Commission on Illumination (ISI) chromaticity diagram shows that at this growth stage, the shells are “white”; i.e. present no absorptions to the visible part. Multivariate statistical analyses based on the intensities of 6 wavelengths show that the shell colour is less variable than the colours of the entire animals. Wavelength intensities of the shells are similar, so no colour trend is visible. On the other hand, the colours of the entire animals are darker, and more variable. At this growth stage, the shell colour is not predictable for a potential selection of receiver or donor.

Tous les grands groupes de parasites de poissons, aussi bien Protozoaires que Métazoaires, ont été signalés chez les Siluroidei. D'après leur localisation, chez l'hôte on peut distinguer: les ectoparasites qui vivent sur le tégument et/ou sur les branchies ; les mésoparasites que l'on rencontre surtout dans le système digestif; les endoparasites qui sont dans le corps (cavités ou tissus). Une accumulation anormale de parasites, par rapport à l'équilibre généralement observé dans la nature, engendre des effets pathogènes chez les poissons en aquaculture. Trois facteurs semblent importants dans le déterminisme de cette accumulation: 1) la vitesse de multiplication, liée au mode de reproduction, en particulier asexué; 2) la taille de l'organisme parasite, qui peut faciliter l'envahissement de l'hôte et 3) le type de cycle biologique, direct (monoxène ou holoxène), ou indirect (hétéroxène). La bibliographie consacrée aux Siluroidei montre que les agents pathogènes ou les parasites les plus étudiés dépendent de la forme d'élevage pratiquée (industrielle ou artisanale). Les parasitoses les plus couramment citées pour leur importance chez Ictalurus punctatus sont détaillées. La question du parasitisme des autres Siluroidei élevés ou potentiellement intéressants est posée.

Deux séries d'expériences ont été menées, les unes en étang de pisciculture, les autres en laboratoire, pour déterminer la relation entre conditions thermiques et durée de l'incubation chez l'Atipa [Hoplosternum littorale (Hancock, 1828)]. En milieu contrôlé, 36 °C constituerait la limite supérieure de la température d'incubation permettant la survie des œufs. La température minimum testée, 24 °C, ne constitue pas la limite inférieure permettant la survie des œufs. La durée minimale d'incubation, évaluée à 36 heures, serait obtenue pour une température d'incubation de 33,6 °C. La quantité minimum d'énergie fournie par l'environnement pour obtenir l'éclosion est exprimée en degrés-heures et s'élèverait à 1 201 °C × h pour la température d'incubation de 31,3 °C. Une typologie du développement embryonnaire de l'espèce, directement inspirée de celle de Ballantyne (1930), a été calée sur une échelle exprimée en °C × h. En étangs, les conditions de température au sein de la ponte, plus élevées que celles de l'air, sont sensiblement identiques à celles de l'eau environnante et relativement stables d'une expérience à l'autre (27 à 29 °C en moyenne). Le temps d'incubation observé sur l'ensemble des 9 nids équipés de capteurs varie de 47 à 54 heures. A temps d'incubation égal, le nombre de degrés-heures nécessaires pour obtenir l'éclosion est plus important en étang qu'en milieu contrôlé. La discussion porte sur le rôle du nid dans la reproduction de l'espèce.

A microcontrolled fish tag which records post-tagging life span, was developed and tested as a prototype. The method of making the tag and the results of tank test trials on chinook salmon (Oncorhynchus tshawytscha) and field trials on chum salmon (Oncorhynchus keta) are presented. This tag was specifically designed to measure survey life (SL) but may have other applications. Survey life is an essential component for area-under-the-curve (AUC) estimation of Pacific salmon (Oncorhynchus spp.) spawning escapements. Accurate escapement estimates are critically important for salmon fisheries management and science. However, AUC spawner estimates must often employ average SL values from historic rather than year-specific studies because direct estimates of SL can require extensive and costly tag-recapture programs. Using assumed SL values can introduce serious bias in population estimates, therefore alternative methods of determining annual SL are important. In this study, the new tag estimated SL by measuring the elapsed time from tagging until the fish came to rest permanently on its lateral or dorsal surface. Details on how to construct the tag are provided so that researchers will be able to make their own.

Conventional “spaghetti” tags and tags originally designed for “sport fishing” and called Betyp tags, were used during a tuna tagging program conducted on board Dakar baitboats in 1999. With the aim of comparing the recapture rate of both types of tags, additional information obtained from previous tagging trips are used in a Bayesian context to set up an informative prior for conventional tags. We show in this study (1) how to account for the sampling uncertainty in the construction of the Beta prior with a likelihood method, and (2) how a simulation-based alternative can be useful for performing the probability density function of the difference between two posterior recapture rates. On the light of the resulting simulated difference we found that Betyp tags have a very strong negative effect on the return rate of bigeye tuna (−19.6% on average). For skipjack the strength of evidence concerning the decrease in recapture rate due to the implementation of Betyp tags (−3.2%) was supported only at a 10% level. The Bayesian approach is compared with the conventional “frequentist” approach and with a likelihood method allowing for the integration of previous information. The results obtained from different approaches indicate that the choice of the method, as well as the choice of the prior, does not modify the conclusion of the study. Potential causes for explaining the lowest efficiency of Betyp tags are discussed.

Catch-at-size data of the eastern Atlantic skipjack were used to estimate changes in total mortality from 1969 to 2007. We used a transitional model of mean length that generalized the Beverton-Holt mortality estimator to allow change in mortality rate under nonequilibrium conditions. Then, from homogeneous periods of time, length-converted catch curves were used to access qualitative changes in selectivity patterns for two surface fisheries (the baitboat fishery operating from Dakar, Senegal, and the European and associated purse seine fisheries). To explore the impact of catch on the mortality rate, a Bayesian change-point analysis was conducted on the catch time series to detect concomitant variation between mortality rates and catch. Finally, potential causes of these changes are discussed in relation to the implementation of new fishing technology, such fish aggregating devices (FAD). The general pattern depicted by total mortality is in agreement with previous knowledge on this fishery: a state of complete or practically complete exploitation during the nineties followed by the decrease in nominal purse seine fishing effort in the last decade, combined with the effect of a seasonal moratorium on FAD fishing operations. There was no evidence of a change in selectivity between the two contrasted periods of time considered: 1969-1979 and 1986-1999; the second period being characterized by the introduction of new technology onboard vessels. In contrast, the covariation over time between total catch and mortality rate three years later highlights the effect of the fishing pressure on the stock of eastern Atlantic skipjack.

Pour un stock donné, les estimations de Prises Maximales à l'Équilibre (PME) obtenues avec des modèles globaux peuvent varier notablement. Dans le cas de la pêche d'albacore dans l'Atlantique Est, elles ont fortement augmenté depuis les années 1970. L'hypothèse présentée ici concerne un modèle global de dynamique de population se modifiant en fonction de l'accroissement de la surface de pêche. Cet accroissement se traduit par une diminution d'une quantité de biomasse jusqu'alors inexploitée. Selon les résultats obtenus à partir de la formulation adoptée, l'augmentation de mortalité subie par le stock serait due à l'augmentation de la surface exploitée plus qu'à celle de l'activité de pêche elle-même.

In this study, the remuneration system applied in the French Guyana shrimp fishery is analyzed in relation to the market changes that this fishery has experienced since 1985. The contract used for the crew members is not the classical share contract usually observed in fisheries. It is a piece rate wage with quality-bonuses. In the classical contract theory literature the piece rate contract is thought to avoid effort shirking but to induce quality shirking. The bonuses are introduced here in order to limit the quality shirking which may occur during grading and storing operations on board. The skippers' contract also differs from the share contract. It is based on remuneration parameters controlled by the companies. By changing these parameters between 1987 and 1991, the companies led the skippers to modify their fishing strategies and especially to concentrate their efforts towards small sized shrimp. The companies thus became able to respond to the increasing demand for small shrimp categories which characterises the French market. The evolution of the spatial distribution of the fleet effort over the same period is consistent with this hypothesis: the fleet has moved towards fishing zones where small shrimp are known to be in abundance.