Cet article propose un modèle empirique du recrutement du stock de coquilles Saint-Jacques, Pecten maximus (L.) en baie de Saint-Brieuc (Manche, France). Ce stock présente de fortes fluctuations du recrutement qui rendent inadéquate l'utilisation des modèles traditionnels de la dynamique des populations exploitées faisant appel à un état d'équilibre. Le modèle intègre trois variables: la biomasse féconde, les effets de l'effort de pêche sur les classes d'âge non exploitées et la variable « température ». Les corrélations entre les différentes expressions des paramètres et le recrutement sont systématiquement analysées. Le choix du modèle final repose sur la minimisation de la part inexpliquée de la variance totale. L'impact de l'effort de pèche sur les fluctuations du recrutement est testé sur deux saisons de pêche avant la mise en exploitation d'une cohorte (groupes d'âge 0 et 1), afin d'intégrer le régime d'exploitation dans le modèle final. Cette procédure révèle un effet plus significatif de l'effort de pêche exercé sur le groupe d'âge 0 de la cohorte.

Pour la température, les expressions initialement retenues sont les anomalies saisonnières, définies comme les écarts de température, par période mensuelle ou bimensuelle, par rapport à la température moyenne de la même période.

Les anomalies saisonnières n'ont pas conduit à une explication significative du recrutement; d'autres expressions de la température ont été recherchées. Elles sont définies comme des anomalies saisonnières pondérées par l'anomalie de l'année correspondante et sont appelées résidus thermiques. Les résidus thermiques sont utilisés sur des périodes mensuelles et bimensuelles en valeur algébrique et en valeur absolue. Les valeurs absolues des résidus thermiques par période bimensuelle fournissent les meilleurs résultats lors des ajustements. Seules les périodes contribuant significativement à l'explication du recrutement sont retenues. La détection de ces périodes critiques est faite par un test de FisherSnedecor. Cette procédure conduit à une combinaison multiplicative de la biomasse féconde, de la mortalité provoquée sur le groupe d'âge 0 par l'effort de pêche et des fonctions exponentielles de résidus thermiques en valeur absolue. Deux périodes critiques sont identifiées, la première quinzaine de mars et la seconde de juillet. La correspondance entre les deux périodes critiques d'anomalie thermique et des étapes du cycle de reproduction de l'animal (le début de la maturation sexuelle, la première ponte et le développement larvaire) est discutée. Le fait que les valeurs absolues semblent plus adéquates indique une adaptation de l'animal aux conditions thermiques moyennes du milieu. La température intervient donc comme un facteur régulant la dynamique de maturation sexuelle et de ponte. Sa rétention sous forme exponentielle multipliant la biomasse féconde traduit les fluctuations inter-annuelles de la fécondité réelle de la population.

The results of preliminary experiments in the development of a hatchery brood stock of whitefish of Lake Geneva, Coregonus shinzi palea Cuv. and Val. (lavaretus), are described. Factors likely to influence the date of spawning and the quality of eggs were studied by reference to the performance of wild spawners from the Lake Geneva. Fish were reared in tanks and the ovulation of females occurred spontaneously at the same spawning time as in wild spawners from the lake. Reared females have produced 30 000 eggs/kg against 45 000 in wild fish. The survival rate of a domestic egg was about 10% less than that of wild females. Since the overripening of the ova was rapid it was necessary to check the ripe females twice a week. The exposure of fish to long days in autumn delayed spawning by two months and permitted the synchronization of hatching under optimal conditions of growth. The ovulations were spread over a period of 3 months when the fish were subjected to long days until spawning. In contrast, termination of the long day regime in December induced a synchronization of the ovulations over just one month.

We analyzed stable isotopes of carbon and nitrogen to investigate the trophic structureof the subtidal food web around the Mingan Islands, northern Gulf of St. Lawrence, easternCanada. All benthic consumers were enriched in 13C (mean δ13C of–17.1‰) compared to particulate organic matter (POM: –23.3‰). Nitrogen stable isotoperatios ranged from 6‰ to 14‰ and the organisms studied fell into three distinct trophicgroups, primary producers, primary consumers (herbivores), and predators. The sea starCrossaster papposus and the sculpin Myoxocephalusscorpius, known to be top level predators, had slightly higher δ15Nthan other predators. Although the average isotope signature of the sea starSolaster endeca placed it among regular predators, the δ15Nincreased with sea star size and large individuals could be considered as top predators.The relatively small number of organisms located at intermediate trophic levels suggests alow level of omnivory in the Mingan Islands’ system, which contrasts with previouslydescribed benthic systems that exhibit a continuum between herbivores and predators. Lowomnivory, in addition to low diversity, suggests that this ecosystem may be relativelyunstable if exposed to natural and/or anthropogenic disturbances such as exploitation andclimate change.

Capelin in the Barents Sea are primarily harvested in a terminal fishery that targets maturing individuals. Theory predicts that, in a semelparous population (i.e., one in which reproduction is seasonal, synchronous, and followed by parental mortality), an unselective, terminal fishery (i.e., one in which most of the fish that are not caught will not have a new spawning opportunity) does not generate strong selection for changed age and size at maturation. The probabilistic maturation reaction norm (PMRN) method was applied to test this prediction and to detect possible temporal changes in length at maturation of Barents Sea capelin between 1978 and 2008. Maturation reaction norms suggest that maturation is age-independent in capelin, but that males require a larger size to attain the same maturation probability as females. No temporal trends in length at maturation could be detected, thus confirming the theoretical prediction. Furthermore, none of the candidate environmental variables tested to explain the temporal variability in length at maturation (water temperature and capelin biomass) consistently showed a significant correlation with the PMRN midpoints.

In the Northeast Atlantic fishery for roundnose grenadier Coryphaenoides rupestris, discards account for about 30% of the catch in weight. Data on discards are scarce; however, length distributions and discard rates appear to be relatively stable from year to year. In contrast, landings data available since 1990 show that the average pre-anal fin length has decreased from 20.7 cm in 1990 to 15.2 cm in 2008, resulting in a 58% reduction of the mean individual weight (850 g in 2008) and an increasing occurrence of overlapping class sizes between landings and discards in recent years. For stock assessment, the method of separable virtual population analysis (SVPA) was used. However, because of the lack of discard data for many of the years covered by the study, the catch data used as input to the assessment model had to be reconstructed from the available information (landings, discards, fishing effort and bathymetric distribution of the stock) using two methods. The first method relied on the assumption that the recent length distributions of discards were applicable to the earlier years (1990-1997). It resulted in unrealistic bimodal length distributions, suggesting a change in discarding practices through time, with larger individuals being discarded in the early days. The second method, based on the fishing effort and length distribution by depth strata, produced unimodal distributions for the whole period and confirmed that the average length of discarded fish was higher in the early days of the fishery. In both cases, the estimates of biomass follow parallel trends, suggesting a strong decline in the population. The available information and methods are discussed.

The application of fisheries acoustics in shallow waters opens new fields of observation and allows new methods for abundance estimates. In this paper we deal with echocounting of migrating fish crossing the Beaucaire-Vallabrègues lock, the first obstacle encountered on the Rhône, using a SIMRAD EY500 split-beam sounder, 70 kHz frequency. Two transducers sampled a section of water and evaluated approximately 35% of the lock section, based on a calibration sphere. The number of fish crossing the lock was calculated for each fish lock. Crossing data for the fish were recorded (dates, position, exit time). The present analysis did not allow the identification of the two major species that cross the dam: shad (Alosa fallax) and mullet (Mugil cephalus). The number of fish counted was positively correlated with the catches per unit effort (CPUE) by recreating fishermen below the dam and with increasing water temperature.

Recirculation aquaculture system (RAS) is the type of land-based aquaculture productionthat interferes the least with the environment, particularly due to low effluent volumeand overall water requirement. Water reuse, sometimes limited by the accumulation of wasteproducts excreted by fish, can be improved by incorporating another biotechnical componentin the form of high rate algal pond (RAS+HRAP), thus adding to the economy and selfsustainability of the system. Our goal was to evaluate whether rearing fish for 1 year ina RAS or RAS+HRAP led to differences in fish production and health, by assessing: (1) fishgrowth; (2) impact on the morphological structure of sea bass target tissues (liver,kidney, and spleen); (3) susceptibility to monogenean parasites; (4) resistance topathogen challenge with Listonella anguillarum; and (5) total bloodprotein. Over the one-year experimental period, sea bass showed no statistical differencesin any parameter evaluated, suggesting that there was a satisfactory purification rate inthe RAS+HRAP system.

Se estudió de contenido en ácidos grasos de los lípidos totales, polares y neutros en músculo, hepatopáncreas y ovario de hembras de Penaeus kerathurus antes y después de la puesta. El ovario fue el organo que presentó un mayor descenso del contenido lipídico total (50,9%), que se transfirió a los huevos durante la oogénesis. En los diferentes organos estudiados, el contenido de lípidos polares fue superior al de lípidos neutros. Sin embargo, durante la puesta se transfirieron mayores cantidades de lípidos neutros que de polares tanto en el ovario como en el hepatopáncreas. El contenido de los ácidos grasos saturados de los lípidos totales del ovario disminuyó un 66,3%, el de monoinsaturados un 56,5% y el de los poliinsaturados un 62,6%. Acidos grasos como el 16:0, 16:1 n − 7 y 18:1 n − 9 contribuyeron de una forma importante a la compositión lipídica de los huevos. Mientras que el 20:5 n − 3 y el 22:6 n − 3 significaron un 4% y un 4,5% respectivamente de los lípidos totales del ovario que se aportaron a la puesta.

The density and movements of fish under ice were studied with single-beam mobile surveys and fixed location split-beam surveys, as well as exploratory fishing in winter-seining areas of two shallow Finnish lakes during winter 1999. Fish schooled near the bottom during the day but the schools dispersed and fish ascended at night. Single and split-beam target strength distributions corresponded fairly closely with the length distribution of seine catch samples. Estimated fish densities were greater at night than in daylight. The swimming speed of smelt (Osmerus eperlanus) was 0.18 m·s–1 in daylight and 0.36 m·s–1 at night. The corresponding figures for vendace (Coregonus albula) were 0.11–0.17 and 0.05–0.08 m·s–1. Nights immediately before and after fishing were the best periods to estimate the effect of seining on fish density. The hydroacoustic fish density estimates at night corresponded closely with seine catches. We conclude that it is possible to estimate the effects of winter-seining by mobile under-ice echo-surveys and catch samples.

By-catch of 0-group flounder, Platichthys flesus L. 1758, in the Loire glass-eel fishery was estimated for 1987 and 1988. Samples were taken throughout the estuary but the by-catch mainly occurred in the Central area. This pattern was observed in both surveys despite different hydrological conditions. The overall by-catch was 41 million animals for 1987 and 7 million for 1988. This difference was not only a consequence of a lowered fishing effort, it also suggests a difference in year-class strength. Recause of the great variability of postlarval distribution the accuracy of the estimates was very poor and only orders of magnitude can be discussed.

The status of an exploited population is ideally determined by monitoring changes inabundance and distributional range and pattern over time. Area of occupancy is a measureof the current distribution. Unfortunately, for many populations, scientific abundance anddistribution information is not readily available. To evaluate the reliability ofcommercial fishing data for deriving occupancy indicators that could serve as proxies forstock abundance, we investigated four questions: 1) Occupancy changes with stock biomass,but is this change strong enough to make occupancy a sensitive indicator of populationbiomass? 2) Fishing boats follow fish, but when does such activity alter the positivemacroecological relationship between occupancy and abundance? 3) When does the activity ofpursuing fish adversely affect occupancy estimates derived from catch and effort data? 4)How does uncertainty in fishing effort data affect occupancy estimates? Spatialsimulations mimicking the dynamics of four deep-water fish species showed thatbiomass-occupancy relationships can be weak. Fishers following fish can modify the spatialdistribution of target species, even reversing the sign of the biomass-occupancyrelationship in certain cases, and can affect the reliability of occupancy indicators,which can also be impaired by error in effort data. Using commercial catch and effort dataand abundance indices for deep-sea fish populations to the west of the British Isles itwas found that only for roundnose grenadier might occupancy provide insights into biomasschanges. In conclusion, care should be taken when using occupancy for evaluating rangechanges in cases where fishing might have modified spatial distributions, uncertaincommercial data are used or when the abundance-occupancy relationship is too flat.

To make a preliminary exploration of the possibilities and limits of magnetic resonance imaging (MRI) for assessing body growth and gonad development of the Pacific oyster, Crassostrea gigas, individual monitoring was conducted on diploid and triploid oysters in their second year, maintained from February to October in a pond on the French Atlantic coast. Magnetic resonance imaging was done on each oyster on five dates during the study period. From these images, variations in the volumes of the flesh, digestive gland–gonad and adductor muscle, and the surface of the gills were measured over time. Apart from the well known differences between diploids and triploids related to maturation of gametes, other original observations of assessing growth were made from these MRI measurements using a non-invasive technique. The standard error of mean dry flesh variation was lower than that found by other commonly used measurement methods. A negative correlation was established between the volume of the gametes spawned and the increase in dry flesh volume after spawning. Moreover, these variations were correlated with the chemical composition of the adductor muscle. All these observations and conclusions need to be confirmed by further observations on oysters of different sizes or grown in different environments.

The spionid polychaete Polydora sp. can live and reproduce inside the oysters' shell, excavating a U-shaped burrow the central portion of which is filled with detritus and particles of dissolved shell. The oyster responds by secreting an organic layer, confining the worm, and later covering it with calcitostracum. This process creates a characteristic "mud blister". Crassostrea gigas were analysed for the organic matrix amino acid content and 14 metals of the whole shell of normal oysters and severely Polydora infested ones. Amino acid, DOPA and FT-Raman analyses were also performed on isolated membranes from the characteristic mud blister and on prismatic layer insoluble matrix (PLIM) of infested oysters, with the aim of detecting any differences between the two organic matrices. Membranes and PLIM composition differ from whole normal shell organic matrix by having lower aspartate and glycine and higher levels of virtually all hydrophobic amino acids, especially alanine. There are no significant differences between membranes and PLIM in the ratio of charged to non-polar amino acids, respectively 0.54 and 0.59. L-DOPA content is also similar in the two matrices with 0.45 (± 0.18) and 0.57 (± 0.30) ng.mg−1 protein for PLIM and membranes respectively. The FT-Raman spectra of membranes is very similar to that of PLIM, suggesting that they have identical composition. Zinc, iron and manganese are significantly higher in infested than in normal shells. Infested oysters can provide an excellent opportunity for investigating normal biological calcification processes.

This study concerns the dynamics and management of the hairtail fishery (Trichiurus haumela) in the East China Sea. Virtual population analysis was used to assess the historical pattern of stock size and an age-structured production model was developed to simulate the historical and future changes of catch and stock of hairtail under different fishing strategies. The results show that the stock of hairtail has been declining in general since the beginning of the 1960s. In 1981, it was 275.103 metric tons, overfished but not very seriously. Subsequent management measures brought some positive effects to stock and catches and slowed down the decline, but they cannot change the status of overfishing of the stock. The current fishing regime will inevitably lead to more severe depletion of the stock and also decrease the catch in the end. To prevent further deterioration of the stock and maintain catches, any further expansion of fishing effort must be stopped. Alternatively, a longer closed season should be introduced or the age at first capture should be raised.

Data from the MEDITS bottom trawl surveys in the Eastern Ionian Sea, covering a depth range of 28 to 845 m were analysed for the period 1998–2008. For each trawling location, environmental and geographical parameters were recorded, while biomass, abundance, biodiversity and size-based metrics were estimated for the total megafaunal community, as well as for four taxonomic sub-communities (Osteichthyes, Chondrichthyes, Crustacea and Cephalopoda) which were expected to respond differently to environmental changes and fishing. In addition, biomass and abundance of ten species selected based on commercial interest, depth range and life history traits were explored, with particular emphasis on deep-sea species. Fishing effort data collected during the study period were analysed and showed a decreasing trend, mainly due to a decrease in the activity of static nets. The relation between the estimated parameters and environmental and spatial factors, as well as temporal (interannual) effects and the effect of fishing effort were explored using generalized additive models (GAMs). Results of GAMs showed that depth and location explained much of the variation in community metrics, probably reflecting mesoscale spatial features and species/communities requirements. Even though the different communities and species exhibited variant patterns in bathymetric and spatial distribution, some common aggregation patterns in productive areas were identified. Despite the relatively short time series, GAMs were effective in detecting increasing trends for several metrics; taking into account spatial factors further contributed to attributing the remaining deviance to temporal effects. These trends were partly explained by the observed decline of fishing effort, which is further supported by the fact that negative relations between several metrics and fishing effort were identified, for some of the selected communities and populations. Abundance, species richness and maximum length proved the most informative metrics concerning the effect of fishing. The current decline in fishing effort in the area seems to be a move in the right direction and should be complemented by additional measures aiming to prevent allocation of effort towards the deep sea.

Tidal embayments in the Bay of Biscay (France) host nursery grounds where common sole, Solea solea, is the most abundant flatfish species. This study aimed to appraise the way those habitats function as nurseries through juvenile sole's responses in somatic growth and condition (Fulton's K) during their first year of occupancy. Field data, two yearly trawling series, taken monthly, were compared with a 6-month-long mesocosm experiment involving reared fish of the same wild origin. Growth rates were compared with predicted maximum growth according to an experimentally established model in relation to temperature. In the field, 0-group sole total length (TL) averaged 130 mm from September onwards in 1999 and 2000. Mean growth rates were 0.7–0.9 mm day−1 in summer and ≤ 0.1 mm day−1 in autumn, when the model predicted 1.4 and 0.9 mm day−1, respectively. In the mesocosm, the growth rates were 0.9 and 0.4 mm day−1 for the same seasons and for stocking densities (300 fish 1000 m−2) about 10 times higher than usually recorded in the field. Wild sole remained in medium condition (K ca. 1 g cm−3) during the entire growing season, whereas they attained a higher K after being released into the mesocosm (1.2–1.3 g cm−3). During the mesocosm experiment, growth was shown to be primarily temperature-controlled: fish reached 150–160 mm (TL) in November. From this investigation, it can be concluded that sole's responses in condition and growth are altered over the whole growing season on nursery grounds. The situation is exacerbated in autumn when the sum of abiotic constraints increases as the competitive biomass does. This indicates impairment of the nursery functioning which, in the context of fish habitat conservation, emphasises the particular vulnerability of embayments to the addition of any further constraint.

Using the example of the New England Regional Fishenes Management Council and its attempts tu manage the fisheries in its area, this paper argues that disferences in the way Nature "operates" constitutes a major source of divisiveness between, on the one hand, those members (and other managers in, say, government) who use linear modeling systems and, on the other hand, the majority of those in the commercial fishing sector who, intuitively, have cast nature in those non-linear terms currently being explored in the Chaos paradigm. Since these two different models have not been explicitly addressed, there is a history of members on each side accusing those on the other of bargaining in poor faith and lacking an adequate understanding of the resource. The thesis of the paper is that making explicit these underlying cognitive modes would provide more "common ground" for addressing management problems in such co-management arenas as the fishery management councils and elsewhere.

The measurement of the fluorescent 4-methyl-7-coumarinylamine released from the hydrolysis of a non-fluorescent peptide model substrate by exoproteolytic enzymes has been adapted to flow injection analysis (FIA). FIA allows samples to be processed very quickly (less than 2 min for triplicate determinations) with good sensitivity (< 0.1 μM) and reproducibility (relative standard deviation < 3% at the 0.2 μM level). In a coastal marine pond, exoproteolytic activity was closely related to bacterioplankton biomass. The high activity measured in pond water (maximum velocity: VM = 1.46 to 2.54 μM.h−1) emphasizes the importance of dissolved protein hydrolysis for bacterial growth and for dissolved organic nitrogen cycling. The mean turnover time of dissolved peptides was 7.6 days, and amino acids liberated by exoproteolytic activity could potentially support, on average, 40% of the bacterial nitrogen demand.

Flatfishes represent an important resource in Portuguese fisheries. Although flatfish landings represent a low percentage of total fish weight landed, their importance is higher when commercial value is considered (11%). Official data on flatfish landings from 1992 to 2005 for all landing ports in Portugal were analysed, together with vessel characteristics, in order to detect patterns in flatfish fisheries. Fleet characteristics were heterogeneous, but most of the vessels were multi-gear. Three landing profiles were identified in the flatfish fishery, and the target species of these métiers showed variation in space and in time. Small vessels caught species that occur in coastal areas, mainly soles, bastard sole, flounder, turbot and brill, and usually also presented high landings of octopuses, cuttlefish and rays. Megrims and spotted flounder were caught with others species, like small pelagic fishes and seabreams by coastal trawlers. For this fleet component, catches of flatfish were usually bycatch. Generalized Linear Models (GLM) were used to analyse flatfish landings (LPUE, landings per unit effort and landings in terms of value) between 1992 and 2005 and to evaluate their relationships with several variables. The main effects in the models included year, month, landing port, vessel length class and total landings (kg). The models explained between 15% and 60% of the variability of the LPUE, and 46% to 82% of the variability of landing value, for the flatfish groups considered, with the most important factors being landing port, vessel length class, month, total landing (kg) and landing port: vessel length interaction. These results suggest high spatial and temporal variability. The results of this study may have implications for fishery management, because the LPUE was highest during the important periods of flatfish life cycles, like the spawning season. This fishing pattern has a negative impact on the stocks because of increased fishing pressure during a sensitive period for these species. The adoption of spatial and temporal closures should be implemented.

Market position and its evolution were analysed in nine key fish and cephalopod species subject to long-term changes, using the Bay of Biscay fisheries as a case study. Although such long term changes have already been documented, and in some cases shown to be related to the impacts of fishing, changes in the physical environment, or both, relatively little work has been devoted to their potential consequences in economic terms. The nature and extent of these consequences was determined in the present study by looking at the composition of the affected fish production, and the status of different fish products on the markets. We propose a methodology to characterize market position for this set of nine species. The selected species represent a significant part of the gross turnover of French fishing fleets operating in the bay. These species were characterized in terms of their potential sensitivity to fishing and changes in environmental conditions due to global warming. We separated species potentially positively (Engraulis encrasicolus and Lophius budegassa) and negatively affected (Pollachius pollachius and Lophius piscatorius) by warming. Evolution of the value of production of the nine species was then depicted using analysis of macro-economic index (production and potential consumption) and price indices. This revealed the relatively high sensitivity of domestic production to the market crisis that occurred in France in the early 1990s, compared to imported and exported products. The relative position of individual species, with respect to the market and its evolution between 1990 and 2005, was analyzed by multi-factorial analysis. Results derived from the analysis clearly distinguish two groups of species, the first characterized by higher prices (monkfish, Nephrops, sole, seabass) and the second by larger volumes available on the French market (pollack, hake, anchovy, sardine, cuttlefish). We conclude that a major part (69 to 87%) of the gross turnover associated with catches of these fish species in the Bay of Biscay remains potentially unaffected by long-term changes related to climate.