Delphine Muths

Multi-genetic marker approach and spatio-temporal analysis suggest there is a single panmictic population of swordfish Xiphias gladius in the Indian Ocean.

Genetic population structure of swordfish Xiphias gladius was examined based on 2231 individual samples, collected mainly between 2009 and 2010, among three major sampling areas within the Indian Ocean (IO; twelve distinct sites), Atlantic (two sites) and Pacific (one site) Oceans using analysis of nineteen microsatellite loci (n = 2146) and mitochondrial ND2 sequences (n = 2001) data. Sample collection was stratified in time and space in order to investigate the stability of the genetic structure observed with a special focus on the South West Indian Ocean. Significant AMOVA variance was observed for both markers indicating genetic population subdivision was present between oceans. Overall value of F-statistics for ND2 sequences confirmed that Atlantic and Indian Oceans swordfish represent two distinct genetic stocks. Indo-Pacific differentiation was also significant but lower than that observed between Atlantic and Indian Oceans. However, microsatellite F-statistics failed to reveal structure even at the inter-oceanic scale, indicating that resolving power of our microsatellite loci was insufficient for detecting population subdivision. At the scale of the Indian Ocean, results obtained from both markers are consistent with swordfish belonging to a single unique panmictic population. Analyses partitioned by sampling area, season, or sex also failed to identify any clear structure within this ocean. Such large spatial and temporal homogeneity of genetic structure, observed for such a large highly mobile pelagic species, suggests as satisfactory to consider swordfish as a single panmictic population in the Indian Ocean.

Isolation and characterization of thirteen polymorphic microsatellite markers from the bluestriped snappers Lutjanus kasmira and L. Bengalensis

This article documents the addition of 92 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Anopheles minimus, An. sinensis, An. dirus, Calephelis mutica, Lutjanus kasmira, Murella muralis and Orchestia montagui. These loci were cross‐tested on the following species: Calephelis arizonensi, Calephelis borealis, Calephelis nemesis, Calephelis virginiensis and Lutjanus bengalensis.

Characterization of thirteen new polymorphic microsatellite markers from the honeycomb grouper Epinephelus merra

Epinephelus merra (Serranidae) is the most common and widespread species of this genus, mostly found in reef habitats from South Africa to Central Pacific. Thirteen polymorphic microsatellite loci were isolated and characterized from this species. Polymorphism was studied in two localities from the Comoros archipelago—Mohéli and Moroni. Allelic diversity was 7.5, polymorphism ranging from 3 to 13 alleles. Overall heterozygosity was high with an average observed heterozygosity of 0.587. Three of these loci were characterised by heterozygote deficiencies for both populations. Finally, ten of the 13 developed primers could be used in future population genetics study of E.merra that might be useful in a context of marine biodiversity conservation.

Characterisation of 22 polymorphic microsatellite loci for the Broadbill Swordfish, Xiphias gladius

The Broadbill Swordfish is harvested by fisheries throughout the world. In order to devise more effective management strategies, we need a clear understanding of the population structure of the species. From a library of 29 tetranucleotide repeats, 22 microsatellite markers were characterised for 94 swordfish samples captured from eastern and western Australia. The number of alleles ranged from 2 to 26 and observed heterozygosity from 0.066 to 0.923. We have identified 18 microsatellites that will be valuable in the examination of swordfish population structure.

Otolith shape as a valuable tool to evaluate the stock structure of swordfish (Xiphias gladius) in the Indian Ocean

Swordfish Xiphias gladius is an oceanic-pelagic species. Its population structure in the Western Indian Ocean was studied from the shape of the sagittal otoliths of 391 individuals collected from 2009 to 2014. Normalised elliptical Fourier descriptors (EFDs) were extracted automatically using TNPC software. Principal components analysis (PCA) conducted on EFDs showed no significant effect of side (i.e. left or right otolith). Consequently, all 391 sagittal otoliths were used to identify stocks among six geographical areas: Reunion Island, Mozambique Channel, Rodrigues, South Africa, Madagascar South and Sri Lanka. To investigate the effects of sex, sampling year, sampling season, lower jaw fork length or geographical area on variations in otolith shape, redundancy analyses (RDAs) with permutation tests were conducted. The first four were non-significant (respectively, p = 0.124, p = 0.721, p = 0.197, p = 0.463), but geographical area appeared to discriminate groups significantly (p < 0.05). Furthermore, linear discriminant analysis (LDA) was performed and overall jackknife classification success reached 30%. Finally, a cluster analysis was conducted using Ward’s hierarchical algorithm, which discriminated three different groups. However, each group consisted of individual samples from all geographical areas. In conclusion, our results were unable to identify a clear geographical separation of swordfish at the Indian Ocean scale, corroborating recent genetic studies in this region.