Strengths and weaknesses in the long-term sustainability of two sympatric seabreams (Argyrops spinifer and Rhabdosargus haffara, Sparidae).

Argyrops spinifer and Rhabdosargus haffara are two sympatric seabream species making important contributions to fisheries landings in the western Arabian/Persian Gulf. We identified the strengths and weaknesses in the long-term sustainability of A. spinifer and R. haffara stocks by integrating multiple sources of data, including fisheries catch and effort statistics, life history traits, scientific trawl surveys and historical length frequency distribution. Four strengths were identified in A. spinifer: wide distribution of juveniles, positive association to the network of de facto fishing exclusion areas created by hundreds of oil-gas facilities, early maturation and the existence of large and old individuals. A. spinifer suffers from two potential weaknesses: slow growth rate and higher exploitation pressure on the small-sized individuals. R. haffara, on the other hand, has a strength of having a short life span and a fast growth rate, characteristics that make it robust to unfavourable conditions. R. haffara suffers from two weaknesses: the lack of association to the oil and gas facilities, and the preference for nearshore shallow waters with stronger negative anthropogenic impacts. Identified strengths and weaknesses of these two sparids provided a preliminary assessment about their long-term sustainability, as well as a roadmap about how to develop different management strategies to meet specific objectives.

Diversity, phylogeny, and historical biogeography of large-eye seabreams (Teleostei: Lethrinidae).

The large-eye seabreams or Monotaxinae is one of two subfamilies in the Lethrinidae, a family of perch-like coral reef fishes. Despite its widespread occurrence and its commercial interest in the tropical Indo-West Pacific (IWP), this subfamily has traditionally been considered a taxonomically difficult group. Based on 268 samples collected from all 15 known large-eye seabream species throughout their distribution ranges, we investigated the taxonomic diversity and phylogenetic relationships in the subfamily. From the results of multiple analyses on four gene markers, we confirmed the monophyly of all four genera in the subfamily (Gnathodentex, Gymnocranius, Monotaxis and Wattsia). We confirmed the occurrence of two species in the genus Monotaxis. We reported 15 delimited species within the most speciose genus Gymnocranius, four of which are potentially new species. The time-calibrated phylogenetic reconstruction enabled us to clarify the evolutionary history of the large-eye seabreams and to infer past patterns of species distribution. The most recent common ancestor to the Monotaxinae likely occurred in the central IWP ca. 32 million years ago. A burst of species diversification likely took place during the Mid- to Late Miocene, coinciding with tectonic change in the central IWP region. This gave rise to most extant lineages in Gymnocranius. The observed geographic distribution patterns in the subfamily most likely point to the central IWP as the area of origin and diversification. This was followed by multiple events of centrifugal range expansion towards either the Indian Ocean or the western Pacific Ocean, or both. Our results thus provide new support for S. Ekman's center-of-origin hypothesis.

Highly regional population structure of Spondyliosoma cantharus depicted by nuclear and mitochondrial DNA data.

Resolution of population structure represents an effective way to define biological stocks and inform efficient fisheries management. In the present study, the phylogeography of the protogynous sparid Spondyliosoma cantharus, in the East Atlantic and Mediterranean Sea, was investigated with nuclear (S7) and mitochondrial (cytochrome b) DNA markers. Significant divergence of four regional genetic groups was observed: North Eastern Atlantic, Mediterranean Sea, Western African Transition (Cape Verde) and Gulf of Guinea (Angola). The two southern populations (Cape Verde and Angola) each comprised reciprocally monophyletic mtDNA lineages, revealed low levels of diversity in Cape Verde and high diversity for Angola despite being represented by only 14 individuals. A complete divergence between North Atlantic and Mediterranean populations was depicted by the mitochondrial marker, but a highly shared nuclear haplotype revealed an incomplete lineage sorting between these regions. Bayesian skyline plots and associated statistics revealed different dynamics among the four regions. Cape Verde showed no expansion and the expansion time estimated for Angola was much older than for the other regions. Mediterranean region seems to have experienced an early population growth but has remained with a stable population size for the last 30000 years while the North Atlantic population has been steadily growing. The lack of genetic structuring within these regions should not be taken as evidence of demographic panmixia in light of potential resolution thresholds and previous evidence of intra-regional phenotypic heterogeneity.

A phylogenetic comparative analysis on the evolution of sequential hermaphroditism in seabreams (Teleostei: Sparidae).

The Sparids are an ideal group of fishes in which to study the evolution of sexual systems since they exhibit a great sexual diversity, from gonochorism (separate sexes) to protandrous (male-first) and protogynous (female-first) sequential hermaphroditism (sex change). According to the size-advantage model (SAM), selection should favour sex change when the second sex achieves greater reproductive success at a larger body size than the first sex. Using phylogenetic comparative methods and a sample of 68 sparid species, we show that protogyny and protandry evolve from gonochorism but evolutionary transitions between these two forms of sequential hermaphroditism are unlikely to happen. Using male gonadosomatic index (GSI) as a measure of investment in gametes and proxy for sperm competition, we find that, while gonochoristic and protogynous species support the predictions of SAM, protandrous species do not, as they exhibit higher GSI values than expected even after considering mating systems and spawning modes. We suggest that small males of protandrous species have to invest disproportionally more in sperm production than predicted not only when spawning in aggregations, with high levels of sperm competition, but also when spawning in pairs due to the need to fertilize highly fecund females, much larger than themselves. We propose that this compensatory mechanism, together with Bateman's principles in sequential hermaphrodites, should be formally incorporated in the SAM.

Early development and occurrence patterns of the Pagrinae seabream Argyrops bleekeri (Perciformes: Sparidae): Does early life history have implications for sparid relationships?

The early development and occurrence patterns of Argyrops bleekeri are described based on 87 specimens collected from Nakagusuku Bay on Okinawa Island in southwestern Japan. Larvae and juveniles of the genus Argyrops are distinguished from the other seabreams inhabiting the Western Pacific region by the strength and extent of head spination, body depth, dorsal-fin-ray counts and melanophore patterns. Argyrops bleekeri is easily distinguished from other members of this genus by the presence of a single rudimentary dorsal-fin spine on the first dorsal pterygiophore, melanophore patterns and an allopatric distribution. Argyrops bleekeri larvae [3.3-7.1 mm body length (BL)] and juveniles (6.7-13.0 mm BL) were found in the bay from January to May; nonetheless, they were not collected from the outer bay or in extremely shallow inshore areas such as tidal flats. The results suggest that Argyrops is the most derived red seabream because of its spiny morphology, and it may be a member of an expanding nearshore group of red seabreams, which originally inhabited offshore waters.

Functional analysis of two MyoDs revealed their role in the activation of myomixer expression in yellowfin seabream (Acanthopagrus latus) (Hottuyn, 1782).

Myoblast determination protein (MyoD), a muscle-specific basic helix-loop-helix (bHLH) transcription factor, plays a pivotal role in regulating skeletal muscle growth and development. However, the regulation mechanism of MyoD has not been determined in marine fishes. In the present study, we isolated the MyoD1 (AlMyoD1) and MyoD2 (AlMyoD2) genomic sequences and analyzed the expression patterns in different tissues of yellowfin seabream (Acanthopagrus latus). The open reading frame (ORF) sequences of AlMyoD1 and AlMyoD2 encoded 297 and 271 amino acids possessing three common characteristic domains, respectively, containing a myogenic basic domain, a bHLH domain, and a ser-rich region (helix III). Phylogenetic and genome structure analyses exhibited classic phylogeny and highly conserved exon/intron architecture. Furthermore, the AlMyoD1 and AlMyoD2 transcription levels were higher in white muscle than in the other tissues. In order to further study AlMyoD function in muscle, promoter sequence analysis found that several E-box binding sites were present. Additionally, binding sites of Almyomixer involved in mammal myoblast fusion, which expression was also the highest in white muscle, were found in the promoter of AlMyoD. Pomoter activity assays further confirmed that both AlMyoD1 and AlMyoD2 can dramatically activate Almyomixer expression, and the AlMyoD1 M2 and AlMyoD2 M5 E-box binding sites were functionally important for Almyomixer transcription based on mutation analysis and electrophoretic mobile shift assays (EMSA). In summary, two MyoDs play a core role in Almyomixer regulation and may promote myofibre formation during muscle development and growth by regulating Almyomixer expression.

Development of a Novel Method for Rapid Discrimination between Wild and Farmed Sea Bream.

A simple method based on direct sampling analysis, coupled with a time of flight mass spectrometer, was developed to discriminate between wild and farmed sea bream on the basis of the docosahexaenoic and arachidonic fatty acid ratio. Good precision in repeatability and reproducibility (relative standard deviation < 15%) was obtained. The fatty acid ratios of the two types of fish were statistically significant (Student's t < 0.001). The use of a simple, rapid, and cost-effective tool could aid in the detection of commercial fish fraud, increase the number of controlled samples, and strengthen control along the entire commercial chain.

Whole genome sequencing reveals the impact of recent artificial selection on red sea bream reared in fish farms.

Red sea bream, a popular fish resource in Korea and Japan, is being bred in fish farms of the two countries. It is hypothesized that the genomes of red sea bream are influenced by decades of artificial selection. This study investigates the impact of artificial selection on genomes of red sea bream. Whole genome sequencing was conducted for 40 samples of red sea bream either from Ehime, Nagasaki and Tongyeong fish farms or from the wild. Population stratification based on whole genome data was investigated and the genomic regions of fish farm populations under selection were identified using XP-EHH and relative nucleotide diversity. Gene ontology analysis revealed that different functions were enriched in different fish farms. In conclusion, this study highlights the difference between independently cultured red sea bream populations by showing that influence of artificial selection acted upon completely different genes related to different functions including metabolic and developmental processes.

Gymnocranius obesus, a new large-eye seabream from the Coral Triangle.

Two previously recorded new species of the large-eye seabream genus Gymnocranius (Gymnocranius sp. D and Gymnocranius sp. E) remain undescribed. Here we describe Gymnocranius sp. E as Gymnocranius obesus sp. nov. This new species is morphologically distinct from all other known species under Gymnocranius by the following combination of characters: relatively deep body, with ratio of standard length to body depth 2.2-2.4; protruding large eye, with eye diameter about equal to or slightly larger than inter-orbital width; caudal fin moderately forked; no blue spots or wavy blue lines on cheek and snout in adults; fourth transversal dark bar on flank running from the sixth spine of the dorsal fin to the origin of the anal fin; anal, caudal and dorsal fins drab with yellowish to yellow margins. Gymnocranius obesus sp. nov. is distinct from G. griseus, with which it has been previously confused by a relatively larger head, scales above lateral line without dark basal patch, and a smaller number of front scales on the dorsal side of the head. Gymnocranius obesus sp. nov. is genetically distinct from its closest known relative, Gymnocranius sp. D by 104 diagnostic nucleotide characters, which translates into a 9.6% sequence divergence at the mitochondrial cytochrome b gene. Gymnocranius obesus sp. nov. reaches a length of at least 295mm. Its distribution, from the Ryukyu Islands to Bali, including Taiwan and the Flores Sea, mostly coincides with the western half of the Coral Triangle.

Identification, Phylogeny, and Function of fabp2 Paralogs in Two Non-Model Teleost Fish Species.

Intestinal fatty-acid-binding protein (IFABP or FABP2) is a cytosolic transporter of long-chain fatty acids, which is mainly expressed in cells of intestinal tissue. Fatty acids in teleosts are an important source of energy for growth, reproduction, and swimming and a main ingredient in the yolk sac of embryos and larvae. The fabp2 paralogs, fabp2a and fabp2b, were identified for 26 teleost fish species including the paralogs for the two non-model teleost fish species, namely the gilthead sea bream (Sparus aurata) and the European sea bass (Dicentrarchus labrax). Despite the high similarity of fabp2 paralogs, as well as the identical organization in four exons, paralogs were mapped to different chromosomes/linkage groups supporting the hypothesis that the identified transcripts are true paralogs originating from a single ancestor gene after genome duplication. This was also confirmed by phylogenetic analysis using fabp2 sequences of 26 teleosts and by synteny analysis carried out with ten teleosts. Differential expression analysis of the gilthead sea bream and European sea bass fabp2 paralogs in the intestine after fasting and refeeding experiment further revealed their altered implication in metabolism. Additional expression studies in seven developmental stages of the two species detected fabp2 paralogs relatively early in the embryonic development as well as possible complementary or separated roles of the paralogs. The identification and characterization of the two fabp2 paralogs will contribute significantly to the understanding of the fabp2 evolution as well as of the divergences in fatty acid metabolism.

Characterisation and expression analysis of cathepsins and ubiquitin-proteasome genes in gilthead sea bream (Sparus aurata) skeletal muscle.

BACKGROUND: The proteolytic enzymes involved in normal protein turnover in fish muscle are also responsible for post-mortem softening of the flesh and are therefore potential determinants of product quality. The main enzyme systems involved are calpains, cathepsins, and the ubiquitin-proteasome (UbP). In this study on Sparus aurata (Sa), the coding sequences of cathepsins (SaCTSB and SaCTSDb) and UbP family members (SaN3 and SaUb) were cloned from fast skeletal muscle, and their expression patterns were examined during ontogeny and in a fasting/re-feeding experiment. RESULTS: The amino acid sequences identified shared 66-100% overall identity with their orthologues in other vertebrates, with well conserved characteristic functional domains and catalytic residues. SaCTSDb showed phylogenetic, sequence and tissue distribution differences with respect to its paralogue SaCTSDa, previously identified in the ovary. Expression of gilthead sea bream cathepsins (B, L, Da, Db) and UbP members (N3, Ub, MuRF1 and MAFbx) in fast skeletal muscle was determined at three different life-history stages and in response to fasting and re-feeding in juveniles. Most of the proteolytic genes analysed were significantly up-regulated during fasting, and down-regulated with re-feeding and, between the fingerling (15 g) and juvenile/adult stages (~50/500 g), consistent with a decrease in muscle proteolysis in both later contexts. In contrast, SaCTSDa and SaMuRF1 expression was relatively stable with ontogeny and SaUb had higher expression in fingerlings and adults than juveniles. CONCLUSIONS: The data obtained in the present study suggest that cathepsins and UbP genes in gilthead sea bream are co-ordinately regulated during ontogeny to control muscle growth, and indicate that feeding regimes can modulate their expression, providing a potential dietary method of influencing post-mortem fillet tenderisation, and hence, product quality.

Functional characterization of polyunsaturated fatty acid delta 6-desaturase and elongase genes from the black seabream (Acanthopagrus schlegelii).

Fatty acid delta 6-desaturase (D6DES) and elongases are key enzymes in the synthesis of polyunsaturated fatty acids (PUFAs) including arachidonic acid (ARA) and eicosapentaenoic acid (EPA) from microorganisms to higher animals. To identify the genes encoding D6DES and elongases for PUFAs, we isolated each cDNA with a high similarity to the D6DES and ELOVL5-like elongases of mammals and fishes via degenerate PCR and RACE-PCR from Acanthopagrus schlegelii. A recombinant vector expressing AsD6DES was subsequently constructed and transformed into Saccharomyces cerevisiae to test the enzymatic activity toward n-6 and n-3 fatty acids in the PUFA biosynthesis. The heterologously expressed AsD6DES produced γ-linolenic acid (GLA, C18:3 n-6) and stearidonic acid (STA, C18:4 n-3) at conversion rates of 26.3-35.6% from exogenous linoleic acid (LA, C18:2 n-6) and α-linolenic acid (ALA, C18:3 n-3) substrates, respectively. When AsELOVL5 was expressed in yeast, it conferred an ability to elongate GLA to di-homo-γ-linolenic acid (DGLA, C20:3 n-6). In addition, AsELOVL5 showed an ability to convert ARA (C20:4 n-6) and EPA (C20:5 n-3) to dodecylthioacetic acid (DTA, C22:4 n-6) and docosapentaenoic acid (DPA, C22:5 n-3), respectively. In these results, the AsD6DES encodes a delta 6-fatty acid desaturase and the AsELOVL5 encoding a long-chain fatty acid elongase shows activity to enlongate C18Δ6/C20Δ5, but not C22.

Geometric morphometrics as a tool for identifying emperor fish (Lethrinidae) larvae and juveniles.

The aim of this study was to evaluate the efficiency of geometric morphometrics for describing the body shape of fish larvae and juveniles, and identifying them to species, in comparison with traditional linear measurements. Species of emperor fishes (Perciformes: Lethrinidae, genus Lethrinus) were chosen as the model group, as the late larval and early juvenile stages in this genus are particularly difficult to identify. Forty-five individuals of different species of Lethrinus were collected from the south-western lagoon of New Caledonia between May 2005 and March 2006. The individuals were first identified to species by their partial cytochrome-b gene sequence. They were then morphologically characterized using eight linear measurements and 23 landmarks recorded on digital photographs. Except for a small proportion of individuals, geometric morphometrics gave better results to distinguish the different species than linear measurements. A 'leave one out' approach confirmed the nearly total discrimination of recently settled Lethrinus genivittatus and Lethrinus nebulosus, whereas traditional identification keys failed to distinguish them. Therefore, geometric morphometrics is a promising tool for identifying fish larvae and juveniles to species. An effective approach would require building image databases of voucher specimens associated with their DNA barcodes. These images could be downloaded by the operator and processed with the specimens to be identified.

Gymnocranius superciliosus and Gymnocranius satoi, two new large-eye breams (Sparoidea: Lethrinidae) from the Coral Sea and adjacent regions.

Two related perciform fish species of the subfamily Monotaxinae (Sparoidea: Lethrinidae) Gymnocranius superciliosus sp. nov. and Gymnocranius satoi sp. nov. are described from specimens and tissue samples from the Coral Sea and adjacent regions. G. superciliosus sp. nov. is distinct from all other known Gymnocranius spp. by the following combination of characters: body elongated (depth 2.7-3.1 in standard length), caudal fin moderately forked with a subtle middle notch, its lobes slightly convex inside, distinctive blackish eyebrow, snout and cheek with blue speckles, and dorsal, pectoral, anal and caudal fins reddish. G. satoi sp. nov. is the red-finned 'Gymnocranius sp.' depicted in previous taxonomic revisions. While colour patterns are similar between the two species, G. satoi sp. nov. is distinct from G. superciliosus sp. nov. by the ratio of standard length to body depth (2.4-2.5 vs. 2.7-3.1) and by the shape of the caudal fin, which is more shallowly forked, its lobes convex inside and their extremities rounded. The two species are genetically distinct from each other and they are genetically distinct from G. elongatus, G. euanus, G. grandoculis, and G. oblongus sampled from the Coral Sea and adjacent regions.

Environmental conditioning of skeletal anomalies typology and frequency in gilthead seabream (Sparus aurata L., 1758) juveniles.

In this paper, 981 reared juveniles of gilthead seabream (Sparus aurata) were analysed, 721 of which were from a commercial hatchery located in Northern Italy (Venice, Italy) and 260 from the Hellenic Center for Marine Research (Crete, Greece). These individuals were from 4 different egg batches, for a total of 10 different lots. Each egg batch was split into two lots after hatching, and reared with two different methodologies: intensive and semi-intensive. All fish were subjected to processing for skeletal anomaly and meristic count analysis. The aims involved: (1) quantitatively and qualitatively analyzing whether differences in skeletal elements arise between siblings and, if so, what they are; (2) investigating if any skeletal bone tissue/ossification is specifically affected by changing environmental rearing conditions; and (3) contributing to the identification of the best practices for gilthead seabream larval rearing in order to lower the deformity rates, without selections. The results obtained in this study highlighted that: i) in all the semi-intensive lots, the bones having intramembranous ossification showed a consistently lower incidence of anomalies; ii) the same clear pattern was not observed in the skeletal elements whose ossification process requires a cartilaginous precursor. It is thus possible to ameliorate the morphological quality (by reducing the incidence of severe skeletal anomalies and the variability in meristic counts of dermal bones) of reared seabream juveniles by lowering the stocking densities (maximum 16 larvae/L) and increasing the volume of the hatchery rearing tanks (minimum 40 m(3)). Feeding larvae with a wide variety of live (wild) preys seems further to improve juvenile skeletal quality. Additionally, analysis of the morphological quality of juveniles reared under two different semi-intensive conditions, Mesocosm and Large Volumes, highlighted a somewhat greater capacity of Large Volumes to significantly augment the gap with siblings reared in intensive (conventional) modality.

Exploring neutral and adaptive processes in expanding populations of gilthead sea bream, Sparus aurata L., in the North-East Atlantic.

Recent studies in empirical population genetics have highlighted the importance of taking into account both neutral and adaptive genetic variation in characterizing microevolutionary dynamics. Here, we explore the genetic population structure and the footprints of selection in four populations of the warm-temperate coastal fish, the gilthead sea bream (Sparus aurata), whose recent northward expansion has been linked to climate change. Samples were collected at four Atlantic locations, including Spain, Portugal, France and the South of Ireland, and genetically assayed using a suite of species-specific markers, including 15 putatively neutral microsatellites and 23 expressed sequence tag-linked markers, as well as a portion of the mitochondrial DNA (mtDNA) control region. Two of the putatively neutral markers, Bld-10 and Ad-10, bore signatures of strong directional selection, particularly in the newly established Irish population, although the potential 'surfing effect' of rare alleles at the edge of the expansion front was also considered. Analyses after the removal of these loci suggest low but significant population structure likely affected by some degree of gene flow counteracting random genetic drift. No signal of historic divergence was detected at mtDNA. BLAST searches conducted with all 38 markers used failed to identify specific genomic regions associated to adaptive functions. However, the availability of genomic resources for this commercially valuable species is rapidly increasing, bringing us closer to the understanding of the interplay between selective and neutral evolutionary forces, shaping population divergence of an expanding species in a heterogeneous milieu.

Resolution of the Acanthopagrus black seabream complex based on mitochondrial and amplified fragment-length polymorphism analyses.

In this study, DNA analyses were employed to verify the identity of six morphologically similar species that occur in the coastal waters of Taiwan: the black seabream complex (Acanthopagrus latus, Acanthopagrus schlegelii, Acanthopagrus sivicolus, Acanthopagrus taiwanensis, Acanthopagrus chinshira and Acanthopagrus pacificus). Amplified fragment-length polymorphism (AFLP) analyses clearly distinguished the same six species that are morphologically diagnosable based on subtle differences in scale counts and anal-fin colouration. In contrast, mitochondrial DNA analyses based on cytochrome b gene sequences did not distinguish individuals of A. schlegelii and A. sivicolus, reflecting either historical introgression or recent speciation and incomplete sorting of their mitochondrial lineages. Phylogenetic relationships among these six north-west Pacific Ocean species of Acanthopagrus analysed using AFLP data were consistent with scale rows above the lateral line (TRac), sperm ultrastructure and geographical distribution. The study provides molecular tools for future research relevant to improved management of these resources, and an increased understanding of the evolutionary history of this radiation.

Stable isotope analysis combined with metabolic indices discriminates between gilthead sea bream (Sparus aurata) fingerlings produced in various hatcheries.

There are few traceability systems other than genetic markers capable of distinguishing between sea products of different origin and quality. Here, we address the potential of stable isotopes combined with metabolic and growth parameters as a discriminatory tool for the selection of fish seeds with high growth capacity. For this purpose, sea bream fingerlings produced in three hatcheries (Spanish Mediterranean coast, MC; Cantabrian coast, CC; and South-Iberian Atlantic coast, AC) were subjected to isotopic analysis (δ15N and δ13C), and indices of growth (RNA and DNA) and energy metabolism [cytochrome-c-oxidase (COX) and citrate synthase (CS) activities] were calculated. These analyses were performed prior to and after a "homogenization" period of 35 days under identical rearing conditions. After this period, fingerlings were discriminated between hatcheries, with isotopic measures (especially δ15N), metabolic parameters (COX and CS), and proximal composition (fat content) in muscle providing the highest discriminatory capacity. Therefore, particular rearing conditions and/or genetic divergence between hatcheries, affecting the growth capacity of fingerlings, are defined mainly by the isotopic imprint. Moreover, the muscle isotopic signature is a more suitable indicator than whole fish for discrimination purposes.

Growth/differentiation factor-11: an evolutionary conserved growth factor in vertebrates.

Growth and differentiation factor-11 (GDF-11) is a member of the transforming growth factor-ß superfamily and is thought to be derived together with myostatin (known also as GDF-8) from an ancestral gene. In the present study, we report the isolation and characterization of GDF-11 homolog from a marine teleost, the gilthead sea bream Sparus aurata, and show that this growth factor is highly conserved throughout vertebrates. Using bioinformatics, we identified GDF-11 in Tetraodon, Takifugu, medaka, and stickleback and found that they are highly conserved at the amino acid sequence as well as gene organization. Moreover, we found conservation of syntenic relationships among vertebrates in the GDF-11 locus. Transcripts for GDF-11 can be found in eggs and early embryos, albeit at low levels, while in post-hatching larvae expression levels are high and decreases as development progresses, suggesting that GDF-11 might have a role during early development of fish as found in tetrapods and zebrafish. Finally, GDF-11 is expressed in various tissues in the adult fish including muscle, brain, and eye.

Genetic differences between wild and hatchery populations of Diplodus sargus and D. vulgaris inferred from RAPD markers: implications for production and restocking programs design.

Restocking and stock enhancement programs are now recognized as an important tool for the management of fishery resources. It is important, however, to have an adequate knowledge on the genetic population structure of both the released stock and the wild population before carrying out such programs. In this study, random amplified polymorphic DNA (RAPD) markers were applied to assess genetic diversity and population structure of wild and hatchery populations of the white seabream Diplodus sargus and the common two-banded seabream D. vulgaris (Sparidae). The estimated values for intrapopulation genetic variation, measured using the percentage of polymorphic loci (%P), Shannon index (H'), and Nei's gene diversity (h), showed high values for all populations. The percentage of genetic variation within D. sargus and D. vulgaris populations, based on coefficient of gene differentiation, reached 82.5% and 90% of the total genetic variation, respectively. An undeniable decrease in genetic variation was found in both hatchery populations, particularly in D. sargus, compared to the wild ones. However, the high values of variation within all populations and the low levels of genetic variation among populations did not indicate inbreeding or depression effects, thus indicating a fairly proper hatchery management. Nevertheless, the results of this study highlight the importance of monitoring the genetic variation of hatchery populations, particularly those to be used in restocking programs. The creation of a genetic baseline database will contribute to a more efficient conservation management and to the design of genetically sustainable restocking programs.