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.

The capacity to bioaccumulate trace metals present in San Jorge Bay, Antofagasta, Chile, was determined in northern scallop, Argopecten purpuratus, to examine the value of this important commercially species as a bioindicator of heavy metal pollution in areas where it is cultured. Scallops were sampled in summer 2009 in four sites: three natural populations (Coloso, Historic District and La Rinconada, marine reserve), and a commercial hatchery (Colorado). The concentrations of three heavy metals (copper, cadmium and lead) were then determined through stripping chronopotentiometric methods, and the levels of four biomarkers: three genes implicated in the stress and oxidative metabolism, i.e., glutathione peroxidase (GPx), glutathione s-transferase (GST) and heat shock protein 70 (HSP70), and a protein marker in the digestive gland and gill, a metallothionein (MT). The Historic District, located in the downtown area of the city, showed the highest metal concentration of all the sampled sites, as well as the highest levels of the four biomarkers. This can be largely attributed to the nearby international port area of the town and high sea traffic flow, exacerbated by the prevailing winds.

The Chilean jack mackerel (Trachurus murphyi) is one of the most important exploited fish populations in the world. Its area of distribution covers the sub-tropical waters of the South Pacific Ocean, from South America up to New Zealand and even Australia. It is subject to high variations in biomass, with annual world catches varying from less than 0.5 to almost 5 million tonnes. Management of this species and its fishery requires a correct understanding of the population structure. Although several hypotheses have been proposed, suggesting that there are up to four independent populations, genetic analysis indicates only a single population in the South Pacific Ocean. We consider the two most probable structures for this population: a “patchy population”, where all the fish belong to a single population that expands and contracts depending on the biomass; and a metapopulation, where a source population creates several subpopulations that can remain independent during prolonged periods, depending on the environmental conditions. We studied the conditions for these hypotheses to represent reality, especially the demographic structure and existence of different spawning areas. Using knowledge obtained from fisheries and acoustic surveys, we show that if we apply their definitions strictly, neither of the two hypotheses can be fully rejected. Nevertheless, some particular spatial characteristics observed recently between the Peruvian and Centre-South Chilean parts of the distribution lead us to conclude that the metapopulation definition is likely to better describe the stock. The consequences of each population structure for fisheries management are listed, showing that the metapopulation hypothesis represents a safer definition for stock assessment. We conclude that T. murphyi can be described as a metapopulation, but also that the definitions proposed in the literature on metapopulations are not fully adapted to pelagic fish populations with a basin-scale distribution range, and suggests specific research that could be done in this field.

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.

Sex ratios in farmed European sea bass are highly biased towards males (75 to 95%), which is problematic for aquaculture. In this mini-review, we re-analyse fisheries literature data about sex ratios in wild sea bass from 13 population samples, representing altogether 4889 individuals covering the major part of the distribution range of the species. We find that as a whole, the sex ratio of wild populations is biased towards females (59.4% females, p < 0.001), but that the sex ratio of the younger fish (<30 cm total length) is balanced (52.0% females, p = 0.15), while the sex ratio of the older fish is heavily biased towards females (69.5% females, p < 0.01). Possible causes of these differences (differential longevity, biased sampling) are discussed. When age-group sex ratios are available (three population samples out of 13), significant variation between age groups appears, part of which is most likely of environmental origin. This study shows that the excess of males in culture is not a characteristic of the species, but rather a consequence of the environments used in culture, interacting with a complex system where both environmental and genetic influences govern sex determination in sea bass.

The presence of piscivorous fish has a significant effect on the structure of fish assemblages. Exotic, piscivorous largemouth bass (Micropterus salmoides) have been introduced to a number of Japanese farm ponds that were originally characterized by a high level of biodiversity. We evaluated the effects of exotic bass on the structure of the fish assemblage following their introduction into the farm ponds. We collected fish and measured environmental conditions in 14 ponds of northeastern Japan. The species richness of pond-dwelling fish assemblages was negatively correlated with the relative abundance of exotic bass. In addition, the relative abundance of lentic cyprinid species (e.g., Rhodeus ocellatus ocellatus, Pseudorasbora parva and Carassius sp.) was negatively correlated with the relative abundance of exotic bass. The abundance of these species was also influenced by environmental factors, including transparency and/or coverage of aquatic vegetation, likely related to their influence on the predatory efficiency of exotic bass. Our results suggest that the structure of fish assemblages in farm ponds with exotic piscivorous fish was influenced by both biotic (i.e., predation) and abiotic factors and that some environmental factors mediate the effects of exotic bass on fish species richness and composition.

Producing high quality cultured black pearls from Pinctada margaritifera is one of the major challenges for the “pearl oyster” industry in French Polynesia. In order to assess donor effect on cultured pearl quality, wild Pinctada margaritifera originating from the Tuamotu Archipelago were used in a duplicated grafting experiment. After 12 months of culture, nucleus retention was assessed and seven pearl quality traits recorded on the 454 cultured pearls harvested from the experiment. The traits scored were nacre thickness and pearl weight, surface defects, lustre, grade, and the colour components: 1) darkness of cultured pearl colour, and 2) visual perception of colour class (bodycolor and/or overtone). Our results demonstrate for the first time that individual wild donors of implanted mantle grafts significantly affect these seven quality traits in P. margaritifera cultured pearls. This finding was repeated in two series of grafts made by different professional grafters. The wild donors could be ranked from “best” (e.g., the donor whose grafts produced the cultured pearl with the maximum lustre) to the “worst”. Moreover, we showed strong correlations between: 1) cultured pearl nacre thickness and grade, with grade A showing the greatest nacre thickness on average compared with grade D and rejects; and 2) nacre thickness/cultured pearl weight and colour components (darkness and visual “colour categories”), with the palest cultured pearls (i.e. white cultured pearls) being the smallest (lowest nacre thickness and weight). Thus, one way of enhancing P. margaritifera foundation stocks for a selective breeding program could be to select the “best” donors, using appropriate molecular tools. Generation of selected donor lines from these stocks through hatchery production would be one way to increase the quality of cultured pearl farming of P. margaritifera in French Polynesia.

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.

The meagre Argyrosomus regius is a large Sciaenid fish known to reproduce in the eastern Atlantic and Mediterranean Sea in just five distinct and restricted geographic areas: along the Mauritanian coast and at estuary openings (Gironde, Tagus, Guadalquivir and Nile). The biological traits of A. regius (high dispersal capabilities, high fecundity, long larval phase, overlapping generations, reproduction until 40 years of age) are, in principle, favourable to high gene flow, which should lead to genetic homogeneity over large geographic scales. Nevertheless, the high geographic distances between the few reproductive areas leads one ask whether there is genetic differentiation in this species. In the present study, the genetic differentiation of the wild A. regius was investigated across most of its natural range from the Atlantic Ocean (France, Portugal, Spain, Mauritania) to the Mediterranean Sea (Egypt, Turkey), using 11 microsatellite markers previously identified in another Sciaenid, the red drum Sciaenops ocellatus. At least two very distinct groups could be identified, separated by the Gibraltar Strait. Genetic divergences (FST values) were intermediate between the Atlantic samples (0.012–0.041), high between Egypt and the Atlantic (0.06–0.107) or Aegean Sea (0.081) and extremely high between the Aegean Sea and the Atlantic (0.098–0.168). A. regius exhibited a very high level of genetic differentiation rarely reported in marine fishes. These results also demonstrate the existence of a sixth independent spawning area in the Menderes delta (Turkey). Factors potentially involved in this very high genetic fragmentation are discussed, including physical barriers, glaciation pulses and biological traits.

European Community regulations on chemicals promote alternative methods to test substances presenting potential risks for the environment. In the present work, cultured atrial cells isolated from oyster (Crassostrea gigas) were used as an experimental model to investigate the toxicity of tributyltin (TBT) after short-time exposure at concentrations representative of those that can be measured in seawater, marine sediments and/or bivalves bioaccumulating this pollutant. In vitro and in vivo assays produce values of the same order of magnitude for both animal/cell survival and heart/cardiomyocyte beating rate. The survival rate of whole animals decreased from 10-6 M TBT after 3 days. For cultured cells, the viability, evaluated using 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay, significantly decreased after two days of treatment with 10-6 M TBT, and after six days with 10-10 M TBT. The percentage of apoptotic cells, quantified by flow cytometry and YO-PRO®-1 iodide, a nucleic acid stain that only permeates cells that are beginning to undergo apoptosis, increased significantly in these cases. Moreover, intracellular concentration of Ca++ had increased after 10 min of exposition to 10-6 M, and could be associated with apoptotic processes. As patch clamp experiments showed that Ca++ conductance was decreased, intracellular calcium increase could mainly be due to a release from internal stores. The decreases in beating rhythm could be explained by the decrease in adenosine triphosphate (ATP) production revealed by 31 P nuclear magnetic resonance (NMR) spectroscopy and confirmed by the increase of the KATP channel conductance. The related hyperpolarization and the disturbances of the energetic metabolism were clearly related to the loss of the atrial cell contractility and viability.

Biological, social and economic information is necessary in order to assess the effectiveness of fisheries management measures. Indicators of the economic performance of fishing vessels are a useful tool for improving management strategies and are necessary for the implementation of the ecosystem approach to fisheries management in European waters. However, they are usually difficult to obtain from official data, which are often biased, incomplete and/or lacking in spatial references. In this paper, a broad set of economic indicators is provided for the fleet operating around the Cíes Islands (NW Spain) during 2008, based on data obtained from interviews with fishers. Artisanal and purse seiners were the most representative segments of the study fleet. While artisanal vessels played an essential social role in Galician fishing communities, purse seiners were a fundamental economic segment as they had the highest profitability per vessel. Both segments appeared to be economically profitable in 2008, with a moderate rate of return on investment for artisanal vessels (around 7%) and a high rate (around 13%) for purse seiners. The present study identified the waters around the Cíes Islands as an essential fishing ground for the study fleet due to the high cash flow that it generated. As part of this area now belongs to a national marine park, our results represent a reference point for decision-makers and for the development of effective management strategies.