Two experiments were developed in France to assess whether growth and processing traits differ for males and females in the European catfish, Silurus glanis. In the first experiment, fish were raised from 5 to 200 g in a pond for 7 months. A significant sex effect is demonstrated in males for live weight at the end of the experiment (males 147.5 ± 5.4 g vs females 132.9 ± 4.9 g) and head index (males 20.6 ± 0.1 % vs females 21.2 ± 0.1 %, P < 0.05). In the second experiment, fish were raised from 885 ± 196 g to 2 266 ± 418 g in a recirculated system at 20.7 ± 1.4 °C for 120 days. A differential growth between the sexes is also registered. Males are heavier and longer (+ 357 g or + 17.0 % and + 6.2 % in length at day 120) and present a higher gutted weight and yield (+ 367 g or + 18.7 %; 95.0 ± 0.9 % vs 93.8 ± 1.8 %) and fillet weight (+ 233 g or + 20.9 %) than females after slaughter.

The gilthead seabream is the most important Mediterranean aquacultured fish species. The main objective of this study was to investigate whether copper sulphate bath treatments used routinely in aquaculture have effects on important physiological functions of early life stages of the gilthead seabream (Sparus aurata). Fingerlings (80–90 days, 0.27 ± 0.06 g) were exposed to copper sulphate baths at 0, 0.25, 0.5 and 1.5 mg L−1 during 24 h. Effects on the central nervous function were evaluated analysing brain acetylcholinesterase activity (AChE). Oxidative stress was assessed by the quantification of lipid peroxidation (LP). Heat shock proteins (HSP70) were used as a general response to chemical stress, RNA/DNA ratio as an indicator of growth, and effects on detoxification function were estimated using glutathione–S-transferases activity (GST). Exposure of S. aurata fingerlings to copper sulphate induced increased lipid peroxidation. In contrast, there were no significant changes in AChE activity, HSP70 levels, RNA/DNA ratio or GST activity. Particularly, the absence of response in GST activity points towards a limited extent of the putative damage caused by the treatments at the highest doses (evidenced through the levels of peroxidation), since this enzyme is directly implicated in detoxification processes involving redox cyclic products. The results suggest that copper sulphate baths at the conditions tested are safe treatments for S. aurata fingerlings.

Oncorhynchus mykiss alevins originating from a monosex female population were treated with methyltestosterone incorporated in the diet (0.5 or 3 mg/kg) for 60 or 90 days from the beginning of first feeding. At sexual maturity the percentage masculinization achieved was high (89-98%) whatever the concentration or duration of treatment. However, the hormone concentration was the major factor in determining the frequency of functional males obtained. Of the 2-year-old neomales produced by the treatment with 0.5 mg/kg diet for 60 days 82% were able to emit their sperm under abdominal pressure compared to only 36% of those produced with 3 mg for 60 days. The increase in the duration of treatment also resulted in a decrease in the number of functional males from 82% (0.5 mg/60 days) to 72.6% (0.5 mg/90 days) and from 35.6% (3 mg/60 days) to 19.2% (3 mg/90 days). It is therefore recommended to use a low dose of hormone (0.5 mg/kg) for only 60 days to get a high proportion of functional males.

Consideration of control rules as part of fisheries management plans is becoming a common practice. Control rules may be simple or complex and utilise model- or observation-based indicators of the status of the stock to control exploitation through limitation of effort or catches. Rules that control harvest (HCR) often utilize commercial fishery data in the calculation of future catches. However, commercial fishery data may be inaccurate and that can compromise the effectiveness of the HCR in maintaining the stock for secure future harvesting. The idea of fishery-independent HCR has arisen because of these problems. Indicators of the status of a stock are derived from standardised fish surveys, commonly trawl surveys repeated annually. A management strategy that relies on such information also requires adoption of appropriate and effective control rules that utilise such information. Here, we draw attention to diverse HCR, including fishery-dependent examples that have been considered, tested or already adopted for fisheries management. Our intention is to stimulate ideas for HCR that are usable with, or adaptable to fishery-independent indicators.

Starting microalgae continuous culture generally includes a preliminary batch culture to obtain sufficient cell density. It is possible to apply continuous regime from the beginning of the culture (IC mode) rather than to begin by an initial batch (IB mode). It is our purpose to check that both initial modes lead to identical steady-state cell characteristics. The microalga Isochrysis galbana affinis Tahiti was used for this comparative study. With an initial cell density of 5 × 105 cell ml–1 and a dilution rate of about 1.0 d–1, both IB and IC modes led to identical cell density once steady-state is reached between 6 and 8 d after inoculation in the two cases. Cell concentration of chlorophyll a and pheopigment a were found to be similar for IB and IC modes at steady-state. Initial culture conditions did not influence saturation irradiance and oxygen consumption rate, which were found to be 650 ± 143 μmol phot m–2 s–1 and 1.54 × 10–3 ± 10–5 μmol O2 ml–1 min–1, respectively. At steady-state, nutrient cell uptakes were ρN = 83.3 ± 2.0 fmol N cell–1 d–1 for NO3– and ρP = 5.5 ± 0.4 fmol P cell–1 d–1 for H2PO4– and did not exhibit significant differences between IB and IC modes. Under the prevailing experimental conditions, results show that IC mode involved very similar steady-state cell characteristics when compared to IB mode subsequent steady-state. IC mode could be an attractive alternative especially for experimental laboratory studies, as it should lead to higher flexibility in starting continuous cultures.

Cryopreservation of sperm is an important component of genetic conservation programs for fish.However, since fish eggs or embryos cannot be successfully cryopreserved and since the mitochondrialDNA is maternally inherited, the mitochondrial genomes of fish populations are presently not beingpreserved in these programs. One method of obtaining eggs from stored materials would be tocryopreserve embryonic cells that could later be transplanted into female recipient embryos, formingchimeras; a proportion of these transplanted cells would be expected to enter the germ line andsubscquently develop into eggs. The hypothesis of this study is that isolated blastomeres of rainbowtrout can be successfully cryopreserved and thawed. The objective of this investigation was to determine if the rate of cooling or the type of container alters cryopreservation success. Isolated blastomeres in a freezing solution containing 8.7% DMSO were subjected to one of two different cooling rates in either 0.5 ml French semen straws or cryovials. Thawed samples were examined using phase contrat microscopy, wkh cells scored as being either intact or non-intact. In the nonfrozen control group, 85.4%f 7.6 ($\bar{x}$ ± S.D.) of the blastomeres were intact. There was no significant difference between the cooling rates used in this investigation based on the proportion of intact cells, but there was a significant (p < 0.002) difference in the proportion of intact cells between samples frozen in French straws (35.9% ± 16.5) and those frozen in cryovials (19.4% ± 4.9).

The Latin American shrimp Litopenaeus stylirostris was introduced in three different Pacific islands (Tahiti, New Caledonia via Tahiti, and Hawaii) and hatchery-propagated for 7–25 generations to develop shrimp farming based on these domesticated stocks. Three microsatellite markers have been used in an attempt to assess the genetic bases of the populations available to start a selective breeding program. The comparison of eight hatchery stocks (five New Caledonian, two Hawaiian and one Tahitian stocks) and one wild Ecuadorian population showed a much lower variability in the domesticated stocks than in the wild population, especially in New Caledonia and Tahiti (2–3.7 vs. 14–27 alleles per locus; 20–60% vs. 90% expected heterozygosity). The Tahitian and the New Caledonian stocks share the same alleles, suggesting that the loss of alleles occurred during the common past of these populations. On the contrary, New Caledonian and Hawaiian populations share only one common allele at the three loci studied. Although the low genetic variability and the resulting inbreeding of the New Caledonian stocks do not seem to affect their present performance, the results of this study demonstrate the usefulness of the introduction of new stocks in order to increase the potential responses to new controlled or uncontrolled selective pressures. The introduction in New Caledonia of the Hawaiian domesticated stocks, which would provide the local shrimp industry with 40% of the allelic diversity of the species, is advised and preferred to the one of wild animals in order to take advantage (i) of the spontaneous selection which occurred during domestication and (ii) of their favourable sanitary "specific pathogen free" status (no presence of four viruses: WSV, YHV, IHHNV, TSV) which limits the risk of introduction of pathogens.

The chromosomes of three commercially important species of veneroid bivalves were studied: Cerastoderma edule (Cardiidae), Venerupis pullastra and Venerupis rhomboides (Veneridae, Tapetinae) using conventional Giemsa staining and morphometric measurements. C. edule showed a diploid chromosome number of 2n=38 and a variable occurrence of supernumerary chromosomes. Its karyotype consists of 12 submetacentric, 4 subtelocentric and 3 telocentric chromosome pairs. The supernumerary chromosomes were easily distinguished by their reduced differentiated size and by their intra and inter-individual variability. C. edule is the first bivalve species where supernumerary chromosomes have been observed. V. ullustra had 2n = 38 with a karyotype including 3 metacentric, 8 submetacentric and 8 subtelocentric chromosome pairs. V. rhomboides had 2n = 38 with a karyotype including 4 metacentric, 8 submetacentric, 4 subtelocentric and 3 telocentric chromosome pairs. Cytotaxonomic relationships are proposed within Tapetinae from comparative analysis of karyotypes of two species studied here and three other species of the same subfamily previously studied.

Nephrops norvegicus (Norway lobster or prawn) is an important target species in demersal fisheries of the north-east Atlantic. Trawling for Nephrops is wasteful when many small fish are caught and discarded in the process. Here, data from 106 commercial fishing trips, sampled between 1982 and 1998 as part of the Scottish discard sampling programme, are used to investigate the fish bycatch and discards of Nephrops trawlers in the Firth of Clyde (west of Scotland). A large proportion of the fish caught in the Clyde is discarded, the discards mainly consisting of small demersal fish (mean length about 19 cm), particularly young whiting (Merlangius merlangus). Within the study period, annual estimates of total fish discards ranged from 318 to 3027 tonnes, with a mean of 1761 tonnes. Fish landings and discards biomass per unit effort both decreased over the study period. However, the decline in landings per unit effort was greater than that in discards per unit effort, corresponding to an increase in the discard rate over time. In recent years, discards have comprised about 70 % of the fish bycatch. The mean length of discarded fish was positively related to mesh size.

The combined effects of feeding time (morning and evening) and dietary fat concentration on feed intake, growth, body composition and lipid tissue distribution were examined in rainbow trout fed on demand. To that purpose, diets with low (LE, 6% lipid) or high energy concentrations (HE, 24% lipid) were used in four treatments that combined provision of the same (HE–HE or LE–LE) or different (HE–LE, LE–HE) diets at morning and evening meals. Digestible energy intakes of the LE–HE (229 kJ kg–1 d–1) and HE–HE (269 kJ kg–1 d–1) groups were significantly different. There was no significant difference in the amount of energy intake between the two meals of the day in any of the treatments. The main effect of dietary treatment was on lipid intake; fish in the HE–HE, HE–LE and LE–HE treatments ingested approximately 3, 2.2 and 1.8 times more lipid than those on the LE–LE treatment. Growth, weight gain and protein gain were not affected by dietary treatment, but lipid gain reflected lipid intake; fish in the HE–HE, HE–LE and LE–HE treatments gained approximately 2.6, 2.1 and 1.7 more lipid than did fish on the LE–LE treatment. Body composition was significantly affected by dietary treatment; whole body lipid content reflected lipid gain, and visceral lipid concentration was affected in a similar way to whole-body lipid. On the other hand, muscle lipid concentrations were similar in fish submitted to the HE–LE, LE–HE, and LE–LE treatments (< 4%), and were lower than in fish on the HE–HE treatment (ca. 5.5%). Consequently muscle lipid concentration was not directly related to lipid intake, because lipid intakes of fish on HE–LE and LE–HE treatments was higher than in those on the LE–LE treatment, while muscle lipid concentration was lower. Thus feeding fish with different diets in the morning and evening might have potential as a tool for manipulating lipid distributions and concentrations without major adverse effects on growth.

Osmoregulation and salinity tolerance were studied in zoeae 1 and instar IX juveniles of Chionoecetes opilio. In zoeae 1, the lower and upper lethal salinities for 50% of the animals (LS 50) at 14 °C were about 10 and 42‰ at 24 h, 18 and 41‰ at 48 h, 25 and 38‰ at 96 h. In juveniles, the approximate 48 h LS 50 s at 6 °C were 13.5 and 46‰. Both developmental stages are able to withstand relatively ample but brief variations of salinity. Their short-term euryhalinity is discussed in relation to the salinity of their habitat. Zoeae were hyper-osmoconformers. Juveniles were osmoconformers and isoionic to the external medium except for Mg++ which was hypo-regulated. Isosmotic and isoionic regulation in post-metamorphic stages are presumably an attribute of the family Majidae. The pattern of osmoregulation in zoeae 1 and juveniles relate C. opilio to the first of three groups of species previously characterized by their pattern of ontogeny of osmoregulation.

The completion of genomic sequences of physiologically important genes frequently revealsnon-coding genetic elements such as tandem repeats (micro- and minisatellites) that areoften more polymorphic than nearby coding sequences. We obtained the complete genomicsequences of three hormone genes in sea bass Dicentrarchus labrax: growthhormone (dlGH), somatolactin (dlSL) and insulin-likegrowth factor-1 (dlIGF-1), including 5′- and 3′-untranslated regions.Mini- and microsatellites were discovered in both flanking and intron regions. Some werepartially conserved across Perciformes. To assess the usefulness and relevance of thesegene-associated markers for understanding population structure, an investigation was madeon genetic diversity and differentiation at four of them in (i) five wildpopulations from the North Sea, the Bay of Biscay and the Western Mediterranean, and(ii) two samples of hatchery-bred individuals from afreshwater-acclimation experiment. Gene and allelic diversities were lower in culturedindividuals than in wild ones. Significant genetic differentiation was demonstratedbetween Bay of Biscay + North Sea and Mediterranean populations(F st > 0.06, p < 0.001),primarily due to dlGH-associated markers. Significant geneticdifferentiation was also detected among the Atlantic and North Sea samples, but restrictedto the locus associated with dlSL. Significant genetic differentiationwas also found among experimental individuals before and after a salinity challenge(F st ≈ 0.05, p < 0.001), but was dueto dlSL and dlIGF-1 loci. Gene-associated markers provedto be more efficient than formerly used anonymous microsatellite markers in providing aclear picture of genetic differentiation.

In the framework of echinoid cultivation, whose objective is to succeed in continuously producing large amounts of edible sea urchins (Paracentrotus lividus) under controlled conditions (aquaculture), gonadal growth is to be optimized. Among the various parameters influencing the production of roe, the quantity of food distributed was tested for optimization. After a 1-month fast, echinoids were fed artificial food pellets (enriched in soybean and fish proteins) for different periods of time over 48 h, the food thus being available ad libitum for 8, 16, 24, 32, 40, and 48 h; the cycles were repeated for a month. The results show that the quantity of food intake and the gonad index peak after about 35 h of food availability. This suggests food should be distributed discontinuously for optimal gonad production and minimal waste.

Les spermes de deux lots de 20 mâles d'une souche de truite arc-en-ciel (Oncorhynchus mykiss) à reproduction printanière, ont été collectés individuellement une fois par semaine pendant 10 semaines. Seuls les spermes d'un volume supérieur à 5 cm3 ont été utilisés pour cette étude. Pour chacun, la concentration en spermatozoïdes, l'osmolarité et les concentrations enzymatiques en glutamique oxaloacétique transaminase (GOT) et stéroïdienne en 17 α, 20 β-dihydroxy-4-pregnen-3-one (17 α, 20 β-OH-P) du plasma séminal ont été mesurées. Des échantillons de spermatozoïdes ont été incubés pendant 1 et 24 heures dans des solutions hypotoniques (60 et 20 mOsm) et leurs réactions (gonflement, éclatement, colorabilité ou non par l'iodure de propidium) ont été analysées. Un échantillon de chaque sperme a été congelé en boulettes à partir desquelles la GOT libérée par les spermatozoïdes après décongélation a été dosée. Des fécondations ont été réalisées avec du sperme frais et du sperme congelé-décongelé.

L'analyse factorielle des correspondances (AFC) entre la fécondante du sperme après congélation d'une part et la fécondante à l'état frais, les caractéristiques physico-chimiques et les résultats des différents tests de qualité membranaire d'autre part, a montré que l'aptitude à la cryoconservation peut être estimée a priori à partir de la mesure de la pression osmotique séminale et de tests reflétant l'intégrité fonctionnelle de la membrane. Ce résultat confirme le rôle déterminant de la membrane lors de la congélation.

The present paper analyzes data collected between 2001 and 2002 on 81 reef fish species targeted by fishers at 5 sites in the Kingdom of Tonga (South Pacific). We first ranked the sites with respect to fishing pressure using two independent methods: (i) Tongan demography and reef surfaces available for fishing, and (ii) the differential effects of fishing on the whole set of 81 species grouped by their life history traits (LHT). We then focused on Parrotfish (Scaridae), which are heavily targeted in coral reef fisheries. We used the identified gradient of fishing pressure to study the effect of fishing on the community structure and test the hypothesis of “shifting dominance” amongst the 20 Scarid species present in the surveys. In addition to the classical effect of decreasing fish size in a family strongly targeted by fishers, the shifting dominance phenomenon includes a decrease in the abundance of the large-bodied and highly targeted species, favouring their replacement by smaller-bodied species from the same family, which are less impacted by fishing. In a context of interspecific competition amongst Scarids, the stress of fishing appears as a factor favouring the replacement of species with large maximum size, and LHT promoting low resilience, by smaller species with the opposite attributes. The discussion focuses on the various processes that can explain the shifting dominance phenomenon. The total density of resilient species, which increased along the gradient of increasing fishing pressure, can be used as an indicator of the over-exploitation of fish communities for reef fisheries management.

In the present study, norepinephrine (NE), epinephrine (E), dopamine (DA) and 5-hydroxy-tryptamine (5HT) have been quantified by high performance liquid chromatography (HPLC) in Pecten maximus during larval and post-larval development. With average values ranging from 2 to 5 pg μg–1 of protein, NE remained low through the whole larval life, while epinephrine (E) was undetected. DA and 5HT were the most abundant monoamines with significant variations between larval, pre-metamorphic and post-larval stages. During the first 20 days, corresponding to D larval and umboned larval stages, levels of DA and 5HT increased from 15 to 30 and 10 to 15 pg μg–1 of protein, respectively. Then during the last week of larval life, at the approach of metamorphosis, DA rose sharply from 30 to 50 pg μg–1 of protein and 5HT from 15 to 50 pg μg–1 of protein. Lastly during the first week of post-larval life (day 27 to day 34) DA and 5HT contents declined to levels similar to those detected in the first days of larval life reaching progressively 1 pg μg–1 of protein during the second week of post-larval life (day 34 to day 55). These rapid and transient variations in monoamine contents (5HT and DA) around metamorphosis, present a great interest. However, this relation between neurochemical changes and metamorphosis must be confirmed with future studies in order to verify if such monoamines might be used as indicators of larval competence in P. maximus, a commercially important species.

F1 hybrids were produced by crossing, in artificial conditions, female Barbus barbus and male B. meridionalis. Results from the genetic study describing enzymatic patterns produced after electrophoresis of experimental F1 hybrids confirmed a great part of the original interpretation of patterns observed in the natural population. Morphological studies which examined denticle length on the last hard ray of the dorsal fin (well developed in B. barbus and absent in B. meridionalis), showed that F1 hybrids' values were not exactly intermediate between the parental values. Up to two years old, experimental hybrids displayed identical growth rates and sexual dimorphism of length (in favour of the females) as B. barbus growing in the same conditions. At this age, in female hybrids, the ovaries matured and produced fertilizable ovules: in male hybrids, the testicles were morphologically normal but no sperm was produced. If this sterility is confirmed in the reciprocal cross (male B. barbus × female B. meridionalis), the phenomenon would be an essential feature in understanding this hybridization.

The European eel (Anguilla anguilla) is drastically declining in all its distribution area and listed in the red list of the IUCN (International Union for Conservation of Nature). A rebuilding plan was adopted at European level in 2007, Regulation R(CE) 100/2007, to restore eel abundance to the level observed during the seventies. Its implementation started on the 1st of January 2009. This species is heavily threatened by numerous activities including fishing, and its management can only be effective through a systemic approach minimizing the whole range of human-induced impacts on the resource and its habitat. In the framework of the European interregional programme INTERREG IIIB-Atlantic Area– the INDICANG project aimed at elaborating abundance indicators of the European eel in the central part of its distribution area (http://www.ifremer/fr/indicang/). A methodological guide was elaborated by this project to define the indicators needed for this resource assessment. In this framework, Ifremer (Institut Français pour l'Exploitation de la Mer) and the UPPA University (Université de Pau et des Pays de l'Adour) have developed a method to estimate the daily and seasonal biomass of glass eels with the view to evaluate the fishery's impact on the estuarine eel recruitment to the Adour catchment. The estimation method uses observations from nightly scientific surveys to estimate glass eels' densities in the water column during various flood tides characterized by different hydrodynamic conditions. Information on these conditions allows the estimation of the glass eels biomass migrating during the night. From these estimates and reported catches made by the fishery during the same night, the exploitation rate applied by the fishery on the flow of glass eels progressing upstream during night flood tides is estimated. The relationship between the exploitation rate, fishery catches and hydrodynamic conditions allowed the estimation of the exploitation rate and nocturnal biomass fluctuations during the fishing season, from November 1st to March 31st of the following year. Finally, from the chronological series of biomass migrating at night, the total biomass migrating every day and the total recruitment into the estuary, during the main glass eel migration period, are estimated. Estimations made between 1998 and 2005 indicate that the overall rate of exploitation of the marine and continental fisheries, on average, is of 15.7%, ranging between 8 and 25% according to fishing seasons.

Though Crassostrea oysters have been distributed and cultured worldwide, their taxonomy is still difficult and often inaccurately determined because of the high level of phenotypic plasticity of the shell morphology. With the help of mitochondrial DNA, two novel species of Crassostrea oysters (C. hongkongensis and C. zhanjiangensis) were recently recognized, which suggests that the species diversity of Indo-Pacific oysters could be underestimated. Utilizing a combination of shell characteristics, a molecular marker (mitochondrial cox1 gene) and phylogenetic analysis, we identified a mangrove-distributed novel Crassostrea oyster species, C. dianbaiensis. The shell morphology of the new species is phenoplastic, as seen in other congeneric oysters. The left valve of this oyster is usually deeply cupped, and the right valve is usually slightly concave. The body size is classified as medium and is approximately 5–10 cm in height (estimated from 20 individuals). One distinctive feature of C. dianbaiensis is that the adductor muscle scars vary in color from dark purple to white in the right valve, but always appear white in the left valve. Based on the cox1 phylogenetic tree, C. dianbaiensis is inferred to be a new member of the Southeast Asia tropical oysters and is believed to be the northernmost distributed species among the tropical oysters. This study provided basal information for future studies, which are necessary to better understand the faunal characteristics, population and roles of this oyster in nearshore ecosystems.

A scattering layer consisting mainly of krill (Meganyctiphanes norvegica) was studied with a submersible transducer, to assess the behaviour of individual organisms in situ by means of split-beam target tracking. Individuals were resolved and tracked, but a rapid increase in average swimming speeds with depth suggested that inaccuracies in the angular estimates affected the estimates. Attempts were made to smooth the tracks during post-processing. Smoothed speeds suggested that most (>78%) invertebrates swam at speeds below 12 cm s–1 (mode ~4 cm s–1), with components of speed larger in the horizontal plane than in the vertical.