Species that occur in low abundances and that are morphologically similar to the target fish are often undetectable in fisheries hauls; however, they add to the catch statistics of the target species. Using mitochondrial DNA and phylogenetic approaches we identified 6 individuals of the species Xenobrama microlepis in a haul targeting the southern Ray’s bream (Brama australis) taken by artisanal fishermen close to Chilean coast. The presence of X. microlepis increases the regional marine biodiversity of fishes in Chilean waters, and fisheries managers should pay attention to the hidden biodiversity in the fishery statistics.
The genus Sprattus comprises five species of marine pelagic fishes distributed worldwide in antitropical, temperate waters. Their distribution suggests an ancient origin during a cold period of the earth’s history. In this study, we evaluated this hypothesis and corroborated the non-monophyly of the genus Sprattus, using a phylogenetic approach based on DNA sequences of five mitochondrial genome regions. Sprattus sprattus is more closely related to members of the genus Clupea than to other Sprattus species. We also investigated the historical biogeography of the genus, with the phylogenetic tree showing two well-supported clades corresponding to the species distribution in each hemisphere. Time-calibrated phylogenetic analyses showed that an ancient divergence between Northern and Southern Hemispheres occurred at 55.8 MYBP, followed by a diversification in the Oligocene epoch in the Northern Hemisphere clade (33.8 MYBP) and a more recent diversification in the Southern Hemisphere clade (34.2 MYBP). Historical biogeography analyses indicated that the most recent common ancestor (MRCA) likely inhabited the Atlantic Ocean in the Southern Hemisphere. These results suggest that the ancestral population of the MRCA diverged in two populations, one was dispersed to the Northern Hemisphere and the other across the Southern Hemisphere. Given that the Eocene was the warmest epoch since the Paleogene, the ancestral populations would have crossed the tropics through deeper cooler waters, as proposed by the isothermal submergence hypothesis. The non-monophyly confirmed for the genus Sprattus indicates that its systematics should be re-evaluated.
Estimating genetic diversity and population structure with polymorphic markers might provide information for the better management of fish that have economic importance. We used the Chilean jack mackerel, Trachurus murphyi, a pelagic species distributed in the south Pacific Ocean, to test the population genetic structure across its distribution. A total of 522 samples were collected from 11 locations in 2008, to be analyzed using six loci microsatellites. We conducted traditional genetic analyses to describe the genetic diversity of T. murphyi and whether it shows spatial genetic structure. The results showed a high genetic diversity across locations (Ho = 0.551 to 0.980; He = 0.676 to 0.959). Estimates for the population structure showed a low and non-significant pairwise FST in all comparisons. We supported the non-genetic differentiation previously reported with the used microsatellite panel. Further comparative temporal studies should be conducted to identify the stability of this pattern. Overall, this study reinforces the hypothesis that, in the Pacific Ocean, Chilean jack mackerel correspond to a large single population.
The anchovy, Engraulis ringens, is an economically valuable fish, and the most heavily exploited resource in the Humboldt Current System. To analyze its genetic structure and diversity, microsatellite markers were developed using 454 pyrosequencing. A total of 27,352 reads containing di-, tri-, tetra-, penta-, and hexanucleotide microsatellite repeat units were identified from 136,537 reads. Among 80 loci containing more than six repeat motifs, 32 primer sets (40%) produced reproducible PCR products, and all of these loci were polymorphic. Some loci showed deviations from HWE and possible null allele's presence, results of an excess of homozygotes. In an analysis of 45 individuals from one E. ringens population, the number of alleles per locus ranged from 2 to 33, observed heterozygosity ranged from 0.171 to 0.976, and the probability of identity values ranged from 0.006 to 0.513. These microsatellites will be useful for numerous ecological studies focused on this important pelagic fish; including the examination of population genetic structure, estimating effective population size and providing information for fisheries management.
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