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The brown trout form the Salmo trutta complex, a diversified assemblage of salmonids. Its native area mainly covers Europe. It can develop three ecological forms or ecotypes, depending on its migratory behaviours: resident, anadromous (going to sea) and lacustrine (going to lakes). The sea trout is the anadromous ecotype, born up river, living at sea where it reaches salmon size, and returning to the river of its birth for spawning. Like other anadromous fish species, this natural ecotype is protected in France. While its distribution along the Atlantic coasts is known, the sea trout is considered absent in the Mediterranean basin. However, some isolated individuals have been observed in the Rhône River and some other rivers from southern France. In order to understand the genetic position of these large specimens swimming upstream in Mediterranean rivers, and despite the degraded DNA due to bad tissue preservation, eight samples of these trout, mainly caught by anglers, were successfully genotyped at seven microsatellite loci and three sequenced at the mitochondrial Control Region. All specimens tested belong to the Atlantic lineage and are probably stocked domestic trout. This study provides preliminary elements for the conservation status of this ecotype in the Mediterranean basin.

Brown trout is a species complex (Salmo trutta complex, L., 1758) including both widespread invasive (non‐native hatchery strains) lineages and endangered local‐endemic lineages, among which is the Sardinian trout, the only native salmonid present in Sardinia. Multiple stressors (e.g. the spread of stocked brown trout of Atlantic origin, habitat alteration and climate change) combine to seriously threaten the persistence of wild native populations.In this study, the origin, population genetics and demography of wild Sardinian brown trout populations were extensively investigated. A total of 274 trout individuals collected from 12 hydro‐geographical basins were analysed using both mitochondrial (control region) and nuclear (LDH‐C1* locus and 10 microsatellites) markers.Although stocking activities have altered the native genetic makeup of some populations in the study area, several (almost) uncontaminated populations showing strong genetic structure were detected. Eroded intra‐population diversity, as well as small effective population size, sometimes associated with a bottleneck signal was also found.The genetic characteristics of Sardinian trout populations described in this study are probably due, at least partly, to the peculiarity of local environmental conditions at the margin of the ecological niche for salmonids.Based on the results of this study, the need for urgent measures of conservation aimed to ensure the near future viability of the last wild Sardinian trout populations was discussed. [ABSTRACT FROM AUTHOR]

Brown trout Salmo trutta L. lives mainly in European rivers and is also bred in hatcheries for fishery purposes. Since the end of 19th century it has been introduced in all other continents. For the present survey most of the known self-sustaining brown trout river populations in Japan have been sampled and analyzed through sequences of the entire mitochondrial DNA control region and twelve microsatellites. In Japan, brown trout are genetically not homogeneous, probably as a consequence of several introductions, one in the Azusa river and at least one other in the remaining territory. The Chuzenji hatchery houses a genetically very distinct strain, probably due to intense manipulation in isolated scientific experimentations over 30 years. Finally, most populations showed high genetic diversity (Mamachi, Kane and Odori streams, Lake Chuzenji) with the exception of the Azusa river samples. This molecular analysis clearly demonstrates a European north Atlantic origin arrived in two distinct ways.

Both morphological and molecular data are presented and discussed for indigenous Salmo sp. from Corsica and Sardinia, here called Tyrrhenian trout. For comparison, morphological data obtained from museum specimens, including the Algerian S. macrostigma, are discussed in the light of recent and new molecular findings. In total, 29 measurements and 20 meristic characters were taken from each specimen. Out of the meristic characters, 12 were obtained by means of X-ray. One important morphometric character in the present study is the size of the head measured from premaxilla to posterior margin of preoperculum. This character was particularly stable in all Tyrrhenian trout, showing relatively large head compared to Atlantic trout and to S. macrostigma. On the contrary, other characters like body punctuations, black and white edges of fins, body depth or number of epurals in the caudal skeleton are quite polymorphic. In certain meristic characters, range of variation of Tyrrhenian trout even exceeds that of the extensive comparative material. Each trout has been genetically characterized. New haplotypes from Tyrrhenian trout were discovered, belonging to three mitochondrial lineages viz. Adriatic, marble and Mediterranean, however, Adriatic haplotypes are dominant. Comparing morphological and genetic data, observed morphology lacks any obvious correlation to mitochondrial lineages and it is concluded that Tyrrhenian trout show no particular affinity to S. macrostigma from Algeria.

The association of molecular variants with phenotypic variation is a main issue in biology, often tackled with genome‐wide association studies (GWAS). GWAS are challenging, with increasing, but still limited, use in evolutionary biology. We used redundancy analysis (RDA) as a complimentary ordination approach to single‐ and multitrait GWAS to explore the molecular basis of pigmentation variation in brown trout (Salmo trutta) belonging to wild populations impacted by hatchery fish. Based on 75,684 single nucleotide polymorphic (SNP) markers, RDA, single‐ and multitrait GWAS allowed the extraction of 337 independent colour patterning loci (CPLs) associated with trout pigmentation traits, such as the number of red and black spots on flanks. Collectively, these CPLs (i) mapped onto 35 out of 40 brown trout linkage groups indicating a polygenic genomic architecture of pigmentation, (ii) were found to be associated with 218 candidate genes, including 197 genes formerly mentioned in the literature associated to skin pigmentation, skin patterning, differentiation or structure notably in a close relative, the rainbow trout (Onchorhynchus mykiss), and (iii) related to functions relevant to pigmentation variation (e.g., calcium‐ and ion‐binding, cell adhesion). Annotated CPLs include genes with well‐known pigmentation effects (e.g., PMEL, SLC45A2, SOX10), but also markers associated with genes formerly found expressed in rainbow or brown trout skins. RDA was also shown to be useful to investigate management issues, especially the dynamics of trout pigmentation submitted to several generations of hatchery introgression. [ABSTRACT FROM AUTHOR]

The oceanic early-life history of Anguilla marmorata was examined in the southwestern Indian Ocean in Mayotte, Mauritius, and Reunion islands through otolith microstructural analysis. The study of the hatching dates, the first feeding check diameter (FFD), the leptocephalus (LD) and metamorphosis (MD) durations, the age at recruitment (AR), and the leptocephalus otolith growth rate (OGR) of glass eels revealed great variations in early-life traits and relationships between them. An agglomerative nesting analysis discriminated three early-life histories, differently represented according to the locality: (i) fast migrants with short LD, short MD, young AR, large FFD, and high OGR dominated in Reunion and Mayotte; (ii) midspeed migrants with intermediate LD, MD, AR, FFD, and OGR dominated in Mauritius; (iii) slow migrants with long LD, long MD, old AR, small FFD, and low OGR were recorded only in Mauritius. All possible strategies were not observed and therefore not successful at the sampling time. However, several were simultaneously expressed, which suggests larval migration plasticity at the population level. This evidence is crucial information regarding both the species dispersal capabilities and the evolution from short-migratory tropical species towards long-migratory temperate ones in the genus Anguilla. L'histoire de vie larvaire d'Anguilla mannorata a ete examinee dans le sud-ouest de 1'Ocean Indien a Mayotte, Maurice et La Reunion, par analyse de la microstructure des otolithes des civelles. Les traits de vie tels les dates d'eclosion, la marque de premiere prise de nourriture (FFD), les durees de vie leptocephale (LD) et de metamorphose (MD), l'age un recrutement (AR) et les taux de croissance de 1'otolithe (OGR), se sont montres variables et diversement correles. Trois types d'histoires de vie larvaire, discrimines par analyse de groupement agglomeratif hierarchique, ont ete observes a l'echelle geographique : (i) migrateurs rapides a LD et MD courtes, AR jeunes, et FFD et OGR importants, dominants a La Reunion et a Mayotte; (ii) migrateurs intermediaires a LD, MD, AR, FFD et OGR intermediaires, dominants a Maurice; (iii) migrateurs lents a LD et MD longues, AR avances, et FFD et OGR faibles, observes seulement a Maurice. Toutes les strategies possibles n'ont pas ete observees et ont donc ete inefficaces pendent la periode etudiee. L'expression simultanee de plusieurs strategies laisse supposer, a 1'echelle de la population, une plasticite de la migration larvaire chez A. mannorata. L'information est cruciale an regard des capacites de dispersion et du scenario d'evolution du genre Anguilla qui suppose une emergence des especes temperees aux migrations larvaires longues a partir des especes tropicales aux migrations larvaires courtes., Introduction The duration of a fish larval stage, and therefore, its metamorphosis timing, might be key factors determining distances of dispersal and species distribution range (Arai et al. 2001x; Hoareau [...]