Whitish parasite-like bodies (PLBs), 0.5–2 μm in size, were detected within the pearl bag of some grafted pearl oysters, Pinctada margaritifera, from Takapoto island (French Polynesia). Histological and ultrastructural investigations have revealed that these bodies consisted of lamellar organic material locally secreted by some epithelial cells of the pearl bag. The fine structure and the formation of these bodies are described. The causes of this abnormal secretion of organic mater, which actually corresponds to periostracum, are not presently known. No parasite nor infectious micro-organism was found associated with the PLBs.

Bien que la chitine soit synthétisée par un grand nombre d'espèces animales, unicellulaires ou métazoaires, appartenant notamment aux groupes zoologiques de la lignée des Coelomates Spiralia, la production de chitine en milieu marin est essentiellement due aux Crustacés. Une étude comparée des quelques données analytiques disponibles a permis de tenter de calculer les valeurs de biomasse et de production de chitine dans quelques grands types d'écosystèmes marins, et d'évaluer ainsi l'importance quantitative de la chitine dans les cycles biogéochimiques du carbone et de l'azote. Les principales données actuellement disponibles concernent le plancton de la baie de Calvi (Corse) en Méditerranée, le krill arctique et antarctique, une population de langoustes des côtes de l'Afrique du Sud, et les communautés benthiques infralittorales à algues photophiles des côtes rocheuses de la Corse. Dans tous les cas, la production de chitine a pu être estimée à environ 1g par an et par m2 de substrat rocheux ou de surface océanique. Sur base de ces valeurs de production et de l'étendue relative des principaux écosystèmes marins, la productiontotale annuelle de chitine par les crustacés marins a été évaluée à ± 2,3 milliards de tonnes.

Gastrointestinal evacuation of inert X-ray dense marker by turbot, Psetta maxima, was followed by use of radiography. Groups of individually tagged turbot aged 1 + years (136.5 g), were held at 16 °C and acclimatized to a feeding period of 4 hours per day. Fish were fed on pelleted feed in excess. The experimental design allowed a test of the effects of handling stress and post-prandial feeding on gastrointestinal evacuation. Repeated handling affected feed intake, but there were no significant treatment effects on gastrointestinal evacuation rate. Fish that ingested large meals displayed higher evacuation rates of markers than fish which ingested smaller meals, but total evacuation time was longer for the fish that consumed the largestmeals. Marker particles started to be voided from the gastrointestinal tract approximately 10 hours following initiation of a meal. and evacuation of marker was completed within 52 hours under the holding conditions employed in the present study.

The mean or average value of a measure or indicator variable used to monitor a fish population can be defined in various ways, each with a correspondingly different statistical estimator for use in the context of a trawl survey. When, as is typical for many species, fish are heterogeneously clustered over space, then scooped in clusters from restricted localities using a trawl, these different estimators can produce different sample mean values with contrasting variations over time, possibly leading to different inferences about the fish population. Two mean parameters and their intuitive estimators, the mean “over fish”, and the mean “over stations”, are discussed and found to present contrasting statistical properties. A third estimator based on fitting a mixed model is proposed which has intermediate properties based on the within-haul correlation. The three estimators are applied illustratively to length data for cod caught in the North Sea by the English groundfish survey from 1992 to 2007. The time series of the mean over stations was smoothest, that for the mean over fish much more variable, and the mixed mean fell between in all years. Variance estimators derived from the fitted mixed model are also put forward. Estimates made from the example suggested that the mixed mean is most efficient. The type of estimator used for the mean should always be considered carefully and mentioned when reporting indicator studies.

To develop selection programs for the great scallop, artificial reproduction of the species needs to be improved by gamete cryobanking. Here, a set of four experiments was designed in order to define the basic elements of a cryopreservation protocol for scallop sperm, including extender composition (experiment 1), cryoprotectant selection (2), cooling rate (3), and assessment of the effects of sperm cryopreservation on sperm motility and fertilization capacity (4). Sperm was collected after serotonin injection (100 μl of a 10-mM solution) and frozen in 500-μl straws. For the first three experiments, the percentage of motile fresh sperm (80 ± 4%, mean ± SEM) was significantly higher than that observed for thawed sperm (11 ± 2%). During the first experiment, no significant difference of the percentage of motile thawed sperm was observed among the three saline extenders tested: seawater, calcium-free Hanks’ balanced salt solution (Ca-free HBSS) and DCSB4 solution. However, a complementary experiment (2) showed that a significantly higher percentage of motile thawed sperm was recorded using DCSB4 than with Ca-free HBSS as an extender. During the third experiment, sperm motility was higher when using polyethylene glycol (10% PEG) as a cryoprotectant, than when using dimethyl sulphoxide, DMSO (10 and 20%), methanol (10%) and ethylene glycol (10% EG). A higher D-larval rate was obtained during the fourth experiment, using fresh sperm than thawed sperm, and using a 500:1 sperm-to-egg ratio compared with a 50:1 ratio. There is some evidence of inter-individual variations in sperm tolerance to cryopreservation. In conclusion, the highest survival of great scallop sperm after thawing was recorded using the following conditions: DCSB4 extender (1:3 vol/vol sperm to extender dilution), PEG cryoprotectant (10%) and straws maintained at 5.5 cm above liquid nitrogen.

In 2009, the European Commission set restricted fishing areas northwest of the British Isles to protect deep-sea vulnerable marine ecosystems and fish stocks. Two protection areas which, historically, have been targeted by fisheries directed at blue ling (Molva dypterygia), were defined. The study aims to assess the effectiveness of restricting fishing activity within the protection areas during the blue ling spawning period (March–May) and to determine whether the existing boundaries are fit for purpose. Estimations of the spatial apportionment of blue ling landings within and outside the protection areas are achieved by combining low-resolution data from fishing vessel logbook entries with higher-resolution vessel monitoring system (VMS) data. High-resolution spatial apportionment of blue ling landings is limited by a lack of high-resolution logbook data, and certain assumptions need to be made on whether vessels are engaging in fishing activity at any individual VMS data point, based on vessel speed and types of fishing gear available. Although current measures appear to have influenced fishing activity in the vicinity of the protection areas, more evidence is needed for a robust evaluation of their effectiveness in protecting blue ling. Recommendations are made for improvements in data collection methods and data availability for research in support of monitoring, assessment and delineation of marine protection boundaries.

A non-destructive method for determining water, protein, lipid and ash content along with lean bodymass (LBM; total body mass – total lipid mass) in live channel catfish was evaluated. This non-invasive technique involved placing the fish within a low-frequency electromagnetic field and measuring the total body electrical conductivity (TOBEC) based on the distinct electrical characteristics of body fat and fat-free tissues. The correlations between TOBEC and whole-body composition were examined using age-1+ channel catfish ranging from 44 to 175 g. Significant linear relationships between TOBEC, body weight, and total length, or combinations of these parameters, and LBM, ash, lipid, protein, and water content were found; r2 values ranged from 0.863 to 0.998. Equations for predicting body composition from TOBEC and morphometric measurements were developed. Analysis of an independent group of fish demonstrated TOBEC equations to be reliable predictors of body composition. This technique should allow successive monitoring of body composition of individual fish at different times and provide additional insight intothe body composition dynamics of channel catfish.

Inter- and intraspecific crossbreeding experiments were conducted to evaluate the aquaculture potential of hybrids in the genus Dicentrarchus, focusing on fertilisation and hatching success. The experimental design consisted of 24 controlled crosses in which individual and pooled fertilisations were made between wild D. labrax individuals (8 dams and 5 sires originating from West Mediterranean and Atlantic populations) and wild D. punctatus (6 sires). Three experiments were successively performed: (1) dams from the Mediterranean population, individually considered to have good egg quality, (2) dams from Mediterranean population, individually considered to have poor egg quality and (3) crossbreeding using pooled eggs from the Atlantic population. In each case, batches of these eggs were fertilized by sperm from males of the two species. Sperm cell quality (concentration and motility) was verified before experimentation in all cases and equal numbers of sperm cells from each male were used to individually (without inter-sire competition) fertilise egg batches. Through the repeated artificial crosses between female common sea bass Dicentrarchus labrax (Linnaeus 1758) and male spotted sea bass D. punctatus (Block 1792), these experiments showed that no post-zygotic reproductive barriers exist to interspecific hybridisation between these two species when using D. labrax as dams and D. punctatus as sires. Phenotypically, the F1 hybrids were easily recognisable: they inherited the characteristic black spots of D. punctatus. Furthermore, embryo survival was significantly higher in interspecific crosses compared with intraspecific controls, showing increased fitness for this trait (increased performance at early life stage). Then, the experimental breeding design validates the observation that West Mediterranean and Atlantic common sea bass populations are different. Indeed, the inter-population crosses (between West Mediterranean dams and Atlantic sires) also revealed increased fitness at early life stages in comparison with the progeny of intra-Atlantic population crosses. However, these individuals were still smaller than their interspecific counterparts. The ability to produce viable F1 hybrids will have significant implications for the practical improvement of sea bass aquaculture.

Uncertainty about reporting rates of tags returned by fishermen has often prevented tagging data from being used in stock assessments. In this study we conduct a meta-analysis to estimate tag reporting rates of commercial tuna fleets by comparing their tag return data with those of the USA longline pelagic observer program. The longline fleets of Venezuela and the USA are estimated to report about 0.8% of tags caught, compared with less than 0.1% for Canadian, Spanish and Japanese longline fleets. For some fleets with sparse return data or for those that do not overlap often with the observer fleet, reporting rate estimates are sensitive to changes in the spatio-temporal resolution over which comparisons are made. Regardless of these sensitivities, the estimated reporting rates are low and there are likely to be large differences in reporting rate between different combinations of flag and gear.

This paper reports the results from three fixed-location acoustic surveys carried out in August and September 1996 to analyse the influence of diurnal behaviour rhythms and water-level fluctuations on the migratory activities of fish in the mouth of the Regelsbrunn-arm east of Vienna, Austria. A BioSonics 105 dual-beam echosounder (420 kHz), with a circular transducer (6°/15°) beaming nearly horizontal across the arm was used, with acoustic ranges of between 20 and 30 m. All surveys were conducted during day and night. The fish density was highest during the first observation period with low water level, lowest during the second sampling period with increasing water level, and intermediate during the third period with decreasing water level. The fish density was always higher during night than during day. Diurnal behaviour rhythms influenced the fish density as well as the size-frequency distribution. Increasing or decreasing water-gauge superposed the influence of diurnal behaviour rhythms on the size-frequency distribution for immigrating fish of certain length classes. Fish within the length group 10–15 cm tended to migrate upstream during decreasing water-gauge. Fish above 400 mm total length tended to move upstream during increasing water-gauge.

In French Polynesia, the black-lip pearl oyster Pinctada margaritifera has been farmed to produce pearls since the 1980s, forming the basis of a major industry. The sustainability of this activity relies on spat collection in the lagoons. However, pearl oyster spat can be difficult to identify for the evaluation of stock variations. It is especially hard to distinguish Pinctada spp. larvae at a very early stage of development. In the present study, a whole-mount in situ hybridisation (ISH) technique was developed to allow the discrimination of larvae of closely-related pearl oyster species found in the French Polynesian atolls. Using specific ribosomal 16S-DNA sequence data, we were able to successfully differentiate between Pinctada margaritifera and Pinctada maculata larvae from 5 to 13 days old. This is the first description of a non-destructive method allowing bivalve larvae discrimination between species within this genus. The method allowed us to successfully identify P. margaritifera larvae in natural plankton samples. This result is a key step needed to develop monitoring of P. margaritifera larval distribution in French Polynesian lagoons, a procedure which will increase spat collection efficiency and ensure sustainable development of pearl oyster farming.

Neosalanx reganius is a poorly studied salangid fish restricted to the upper reaches of the Chikugo and the Midori River flowing into the Ariake Bay, Kyushu, Japan. Samples of N. reganius were collected from brackish water areas of the Chikugo River by eight cruises in 1998-2004 to characterize the distribution pattern, feeding ecology in relation to ambient prey concentrations, fecundity and condition of the fish. A total of 244 specimens were collected, 36 to 71 mm total length, and 111 to 1301 mg body weight. The catch per unit of effort (CPUE; number of fish collected by towing a larva net for 20 min) correlated positively with turbidity and negatively with salinity. N. reganius is a planktivorous fish, fed on a single calanoid copepod species Sinocalanus sinensis, which was the single most dominant prey item in all stations during all cruises, contributing as high as 97.0% of the total diet of the fish; the other prey items (other calanoids and cyclopoids, Daphnia sp. and decapod mysid) together contributed only 3%. S. sinensis also dominated in the environmental copepod composition. The CPUE showed significant correlation with copepod dry biomass which increased upstream (r = 0.90; p < 0.05). Fecundity ranged 347-995 (mean 583 173) oocytes individual−1 and relative fecundities ranged 6.8-15.6 (mean 10.1 ± 2.4) oocytes mm−1 TL and 0.8-2.5 (mean 1.6 ± 0.5) oocytes mg−1 of net body weight (weight taken after gonad extraction). Fecundity showed significant positive relationship with fish length and body weight. GSI ranged 29.4-58.8% (mean 43.5 ± 7.9%) and had significant relationship with fish length and body weight. Spawning individuals had higher allometry coefficient (b) and condition factor (K) than the non-spawning individuals. The oligohaline upper Chikugo estuary provides important feeding and spawning grounds for the fish with sufficient prey abundance and turbidity maximum that seemed advantageous for feeding and spawning of N. reganius in the Chikugo estuary. We suggest that future research should emphasize on the spawning and early life ecology of the fish in order to formulate effective conservation action.

The ability to accurately quantify ovarian condition in cultured species of fish is of paramount importance in the understanding of their reproductive biology and the development of appropriate culture conditions. Here, we discuss stereological analysis, a mathematically proven technique that determines 3-dimensional topology and geometry from 2-dimensional thin sections, as a safer and more precise replacement for existing methodology.

A number of European fishing fleets have been regulated through a combination of quota and effort (sea days) controls since 2004. These two regulation schemes are, however, interrelated, i.e. a given quota limit will necessarily determine the effort used and vice versa. A bioeconomic feedback model is presented which takes this causality between effort and harvest control into account, and switches back and forth between these two regulation schemes depending on which is the binding rule. The model is based on biological stock projection, and quotas are set using the Pope approximation while an economic production function is used to estimate the harvest when the effort is binding. The economic response of the fleet is modelled through a dynamic investment/disinvestment module which evaluates the change in the fleet capacity given the economic outcome of the fishery. A simple example is presented for the Danish seiners catching cod in the North Sea. The model has been constructed as part of the 6th framework project “Operational Evaluation Tools for Fisheries Management Options (EFIMAS)”.

Tilapia cameronensis fry were reared in plastic tanks and earthen ponds at the Fishculture Research Station, Foumban, Cameroon. Their growth rate was compared to that of the Nile tilapia (Oreochromis niloticus) fry, reared under identical conditions. Different treatments were applied (food or organic manure only; food combined with organic manure); physical-chemical variables were quantified. The best growth rate was recorded for fry reared in tanks receiving both food and organic manure: the daily weight gain of T. cameronensis fry in tanks was nearly half of that of the Nile tilapia, while in ponds T. cameronensis showed a higher growth rate than O. niloticus (0.19 g.d−1 versus 0.13 g.d−1). The growth rate decreased with increasing stocking density. In another experiment Tilapia cameronensis fry were reared in aquaria at different stocking densities in a recirculated water system. The highest growth rate was recorded for fry stocked at 0.5 fish.l−1 and receiving daily a feeding rate of 15% of the total biomass. This growth rate was comparable to that of fry stocked at 0.25 fish.l−1 receiving the 5% feeding rate. The latter had the lowestFCR. Mortality due to aggressive interactions increased with decreasing stocking density.

This paper traces the evolution of snow crab fisheries science and its impact on the management of the southern Gulf of St. Lawrence snow crab (Chionoecetes opilio) fishery. This currently lucrative fishery (estimated landed value of more than 125 million Canadian dollars in 1994) has experienced the traditional rises and falls of most fisheries and the resulting socio-economic consequences and sometimes strained relations between the industry and the fisheries management agency, in this case the Canada Department of Fisheries and Oceans (DFO). Of note at this time is the remarkable degree of cooperation that has developed between the industry and DFO since the stock has drastically decreased (1987–1989). Since then the stock has been recovering steadily and is also better managed. The reasons for this are four-fold: (1) arecruitment pulse of small-sized crab occurred in 1988–1989; (2) substantial advances in the understanding of the complex biology of snow crab and the development of an accurate, reliable stock assessment methodology together have provided consistent, reliable and credible advice for forecasting the amount and geographic distribution of exploitable biomass for the upcoming fishing season; (3) the industry leaders worked very hard with their associations to convince fishers that their fishery was in peril and that close cooperation with DFO was the key for the future; (4) the industry and DFO (fisheries biologists and managers) worked as partners to develop a management approach based upon scientific advice to climb out of the trough. The paper also outlines the conundrum that fisheries managers currently face resulting from a combination of a moratorium of the entire Gulf of St. Lawrence groundfish fishery, the consequent pressure from displaced groundfish fishers to enter the lucrative snow crab fishery and an optimistic shortterm but pessimistic longer term forecast regarding snow crab abundance: do we redistribute the wealth; if so among whom and how and for how long?

The relationship between serum protein, immunoglobulin concentrations and protein molecular weight profile (PMWP) alterations of sea bass (131.3 ± 4.3 g) reared in sea water with sublethal concentrations of ammonia was studied over two periods totalling 116 days. During the exposure period (62 days) the first group (group 1) lived in sea water with 0.204 mg·L−1 unionized ammonia nitrogen equivalent to 12 % of the lethal concentration for 50 % of a population exposed for 96 h to ammonia (96-h LC50), whilst the second group (group 2) lived in sea water with 0.340 mg·L−1 UIA-N equivalent to 20 % of the 96-h LC50 of ammonia. Then, the two groups were left for a recovery period (54 days) in the same water as the control group (group 0). The determination of the total immunoglobulin (Ig) concentration was carried out by enzyme-linked immunosorbant assay (ELISA). Gel filtration columns were used for the serum PMWP. Serum Ig concentration of the exposed fish (group 2: 1.76 ± 0.43 mg·mL−1; group 1: 1.19 ± 0.33 mg·mL−1) was lower than the control group 13.39 ± 1.01 mg·mL−1) after 21 days of exposure period but this difference was reduced at the end of this period (day 62) and treated group Ig concentrations switched to higher than the control group after the recovery period (day 116, group 2: 9.75 ± 1.84 mg·mL−1; group 1: 7.50 ± 1.22 mg·mL−1 group 0: 6.38 ± 1.13 mg·mL−1). In fact, at the end of the experiment, the cumulative Ig production difference between fish exposed to ammonia and the control was less than 10%. Although a similar evolution of the Ig serum occurred with protein concentration, the serum protein concentration deficit of group 1 was restored at the end of the exposure period (group 2: 46.49 ± 2.34 mg·mL-1; group 0: 46.74 ± 1.97 mg·mL−1) and the cumulative production during the experiment was not significantly different between group 1 and group 0. However, this remained lower for group 2. During the exposure period, the PMWP of treated fish moved towards smaller molecular weight proteins. This alteration of the PMWP showed that the 0.2-kDa fraction increased, and another fraction appeared at the end of the exposure period. However, at the end of the recovery period, no difference was found between the PMWPs of control and treated fish. The alterations of the serum protein and Ig of fish reared, for a limited period (2 months), in water with sublethal concentrations of ammonia (20 % 96-h LC50 or less) should disappear completely after a few months in normal rearing conditions.

Human growth hormone like peptides were present in Penaeus indicus as two molecular forms: one with a molecular weight about 25 kDa which is similar to that of the vertebrate growth hormone and a smaller form of 2 kDa. Quantitative variations of hGH-like peptides in different larval stages of three species of Penaeids (Penaeus vannamei, P. stylirostris, P. indicus) suggest a possible involvement of hGH-like peptides in the development. Human growth hormone (hGH) supplementation in the diet of Penaeus vannamei larvae seems to have a positive effect on the size and on the quality of the animals estimated by their resistance to salinity stress.

Fish stock assessment makes Widespread use of Virtual Population Analysis (VPA) and long-term equilibrium prediction models. Although there have been some statistical investigations about the properties of VPA results, apparently there are no complete analyse about predictions statistical and numerical behaviour. However, management decisions generally rely upon production forecasts. This paper compares stability properties of VPA and the yield per recruit model with regard to various errors concerning all the input parameters. Robustness fis assessed by means of first-ordo sensitivities whereas variances are inferred from delta-method estimators. Sensitivity of yield per recruit appears to be mainly due to terminal mortality rate and age-specific weights, and to a lesser extent, to catches and natural mortality. Mean values of the input parameters were also found to influence the model's behaviour. A complete estimation of variances would require a variance-covariance matrix for weights at age and terminal fishing mortality rates. Sensitivities and variances are complementary in that the first quantify the absolute robustness of the models whereas the second show model robustness in relation to the dimensioned interval of variation of each input parameter. If variances were available for all parameters, yield per recruit estimates could be taken into account for fisheries management decisions.

A physiological model has been developed to provide a simulation of scope for growth responses of cockles Cerastoderma edule to environmental factors such as temperature and seston parameters. As in previous treatments, model structure consisted of a series of equations representing the vanous physiological processes which are integrated in the energy balance of filter-feeders. Unlike these treatments, however, the present model was designed to give account of the separate processing of phytoplankton and detritus, as components of suspended food that are submitted to differential selection and absorption. In this way, effect of quality indexes based on phytoplankton abundance on growth rates could be explored. Subsequently, we have applied this model to: (a) simulating scope for growth under conditions subjected to variation in the estuarine media, and (b) predicting growth variability as a function of food regime, by comparing two particular estuaries with contrasting seston characteristics.