BackgroundThe Malabar snakehead Channa diplogramma is one of the most enigmatic and least understood species within the family Channidae, which comprise one of the most important groups of freshwater food fish in tropical Asia. Since its description from peninsular India in 1865, it has remained a taxonomic puzzle with many researchers questioning its validity, based on its striking similarity with the South East Asian C. micropeltes. In this study, we assessed the identity of the Malabar snakehead, C. diplogramma, using morphological and molecular genetic analyses, and also evaluated its phylogenetic relationships and evolutionary biogeography.Methodology/Principal FindingsThe morphometric and meristic analysis provided conclusive evidence to separate C. diplogramma and C. micropeltes as two distinct species. Number of caudal fin rays, lateral line scales, scales below lateral line; total vertebrae, pre-anal length and body depth were the most prominent characters that can be used to differentiate both the species. Channa diplogramma also shows several ontogenic color phases during its life history, which is shared with C. micropeltes. Finally, the genetic distance between both species for the partial mitochondrial 16S rRNA and COI sequences is also well above the intra-specific genetic distances of any other channid species compared in this study.Conclusions/SignificanceThe current distribution of C. diplogramma and C. micropeltes is best explained by vicariance. The significant variation in the key taxonomic characters and the results of the molecular marker analysis points towards an allopatric speciation event or vicariant divergence from a common ancestor, which molecular data suggests to have occurred as early as 21.76 million years ago. The resurrection of C. diplogramma from the synonymy of C. micropeltes has hence been confirmed 146 years after its initial description and 134 years after it was synonymised, establishing it is an endemic species of peninsular India and prioritizing its conservation value.

We record here the invasion of the African sharp-tooth catfish Clarias gariepinus in the South China biodiversity hotspot, an area rich in endemic and endangered fish fauna. C. gariepinus was introduced into the natural systems as escapees from aquaculture ponds. These catfishes are very large, top predators, and thus have the potential to cause serious threats to the native fish fauna. The impact of C. gariepinus needs more investigation with emphasis on developing techniques for controlling its dispersal.

Rock carp Procypris rabaudi is a vulnerable endemic fish in the upper Yangtze River. Hatchery release has been carried out as a major stock enhancement strategy for this species. Ten microsatellite loci were chosen to compare genetic variation between one wild population and two hatchery groups to evaluate the potential impacts of hatchery release on the genetic structure of the wild population. Two different models indicated strong evidence of recent bottlenecks in all groups. The hatchery groups were lower in the mean number of alleles per locus, allelic richness, and allelic diversity compared with the wild population. The 80% membership coefficient indicated that 14% of the wild fish could be assigned as hybrids of wild and hatchery fish. Our results suggested that hatchery release will further reduce the natural genetic diversity in the wild population, change the genetic structure of the rock carp population, and may not benefit restoration of this vulnerable fish species.

SummaryFishery harvest of Coilia mystus in the Yangtze Estuary has declined dramatically since the late 1990s. A full understanding of the reproductive biology of this species is essential for effective management of the population. A total of 1072 females of C. mystus collected from the Yangtze Estuary area between May 2006 and September 2007 were analyzed to reveal the general reproductive biology of the population. Females with increased gonadosomatic index (GSI) and gonads developed to stages IV and V occurred mainly from March through August, indicating a major spawning season in this period; there were also a few females with increased GSI and developed gonads observed in November and January. Absolute fecundity (AF) ranged from 3093 to 36 786; and increased with both body weight (BW) and age. The relationship of AF to BW was fitted to a linear function AF = 924.72 · BW)414.17 (r 2 = 0.82, n = 134, P < 0.05). Relative fecundity was 871 eggs per gram. Oocyte diameter (OD) of mature females ranged from 0.55 to 0.90 mm with a mean (±SD) of 0.71 ± 0.05 mm (n = 3927), independent of BW. The frequency distribution of OD showed a single mode and histological examination demonstrated that the development of oocytes was synchronous within an ovary, suggesting that C. mystus is a single spawner. Compared to previous studies, females in this study tended to produce more but smaller eggs. This increased fecundity may represent biological compensation for the decline in abundance of the population due to overexploitation.