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The maintenance of genetic diversity is one of the chief concerns in the captive breeding of endangered species. Using microsatellite and mtDNA markers, we examined the effects of two key variables (parental number and duration of breeding period) on effective population size (Ne) and genetic diversity of offspring in an experimental breeding program for the endangered Tokyo bitterling, Tanakia tanago. Average heterozygosity and number of alleles of offspring estimated from microsatellite data increased with parental number in a breeding aquarium, and exhibited higher values for a long breeding period treatment (9 weeks) compared with a short breeding period (3 weeks). Haplotype diversity in mtDNA of offspring decreased with the reduction in parental number, and this tendency was greater for the short breeding period treatment. Genetic estimates of Ne obtained with two single-sample estimation methods were consistently higher for the long breeding period treatment with the same number of parental fish. Average Ne/N ratios were ranged from 0.5 to 1.4, and were high especially in the long breeding period with small and medium parental number treatments. Our results suggest that the spawning intervals of females and alternative mating behaviors of males influence the effective size and genetic diversity of offspring in bitterling. To maintain the genetic diversity of captive T. tanago, we recommend that captive breeding programs should be conducted for a sufficiently long period with an optimal level of parental density, as well as using an adequate number of parents. © 2011 Wiley Periodicals, Inc. Source

Nakagawa H.,Kyoto University | Nakagawa H.,Hiroshima University | Seki S.,Kochi University | Ishikawa T.,Tochigi Prefectural Fisheries Experimental Station | Watanabe K.,Kyoto University
Ichthyological Research | Year: 2015

The genetic population structure of the Japanese amblycipitid catfish Liobagrus reinii was investigated using partial sequences of the mitochondrial DNA cytochrome b gene, focusing on the pattern associated with the Central Highlands (the Fossa Magna region), the major geographic barrier for Japanese freshwater fish. Phylogenetic analyses revealed two highly divergent lineages within this species (clades 1 and 2), with each lineage further divided into three or four allopatric subclades (1-1, 2, 3, 4 and 2-1, 2, 3), suggesting that geographic isolation, such as mountain uplifting, was the major factor influencing population structure. One exception was the co-occurrence of two subclades (1-1 and 2-1) in several rivers of the Chugoku and Shikoku regions of western Japan, which would have resulted from a secondary contact between historically isolated populations via river capture. Subclade 1-2 haplotypes were widely distributed in the central area of Honshu Island (Pacific side) across the Central Highlands, where population and species differentiations are often evident in freshwater fishes. This pattern, along with circumstantial evidence, supports the theory that eastern populations from the Pacific side of Honshu originated from artificial introduction. Together with the western limit of the northeastern populations on the Sea of Japan side of Honshu, the role of the Fossa Magna region as a geographic barrier was emphasized also in this species. Based on the deep intraspecific divergence of the species and large differentiation from continental congeners, L. reinii was concluded to be an old member of the Japanese freshwater fish fauna, which extended its distribution over the Japanese Archipelago at an early time. © 2015 The Ichthyological Society of Japan Source

Kubota H.,Tochigi Prefectural Fisheries Experimental Station | Watanabe K.,Kyoto University | Suguro N.,Kanagawa Prefectural Fisheries Technology Center | Tabe M.,Baika High School | And 2 more authors.
Conservation Genetics | Year: 2010

The Tokyo bitterling Tanakia tanago (Cyprinidae) was once found throughout the Kanto Plain, central Japan, but most of their habitats have been lost due to human activities such as urbanization and improvement of paddy fields. Subsequently, conservation efforts, including captive breeding and reintroduction, have been ongoing. However, the genetic relationships among populations of this species including captive and remnant wild populations have been uncertain and thus management units for this species have been unidentified. We examined the population differentiation among 12 populations, including four wild and eight captive populations, and their relative genetic diversities to assist in conservation management decisions. Phylogeographic analyses based on partial mitochondrial cytochrome b gene sequences and microsatellite polymorphisms revealed four geographically associated genetic groups in the populations. Northern Tochigi populations have diverged from other populations (0.77% of dA), likely stemming from allopatric fragmentation following a change in the route of the Naka River, which occurred during the middle of the Pleistocene epoch. Microsatellite analysis has revealed that the genetic diversity of each population is generally low, and that most of the populations have experienced genetic bottlenecks. For future in- and ex-situ conservation programs to succeed, the population structure and genetic variability of remnant populations need to be taken into consideration. © 2010 Springer Science+Business Media B.V. Source

Ishikawa T.,Tochigi Prefectural Fisheries Experimental Station | Mano N.,Nihon University | Minakami K.,Nihon University | Namba A.,Nihon University | And 3 more authors.
Fish Pathology | Year: 2013

Although dietary supplementation with high-concentration ascorbic acid (AsA) can be a promising approach for reducing fish losses due to infectious hematopoietic necrosis (IHN), ineffective cases of AsA supplementation have occasionally been reported in fish farming operations. In the present study, we investigated the influence of viral strains and fish sizes on the efficacy of AsA supplementation in rainbow trout Oncorhynchus mykiss and kokanee O. nerka. Fish with different body weights were fed commercial diets supplemented with 5,000 mg of AsA per kg of diet for 7 days, and then challenged by bath exposure with two IHNV isolates (TK8901 and TV0026) belonging to different genogroups. AsA supplementation in the diet did not significantly reduce the mortality of 1-g rainbow trout as a result of infection with either isolate. On the other hand, the mortality of 2-g kokanee and 6-g rainbow trout fed AsA decreased significantly against TV0026 infection. The efficacy of AsA against TK8901 infection was, however, not confirmed with these fish sizes. These results revealed that differences in IHNV strain or fish size can affect the efficacy of high-concentration AsA administration in IHN of farmed salmonid fish. © 2013 The Japanese Society of Fish Pathology. Source

Ishikawa T.,Tochigi Prefectural Fisheries Experimental Station | Mano N.,Nihon University | Nakanishi T.,Nihon University | Hirose H.,Nihon University
Fisheries Science | Year: 2011

The present study examined the effects of high-concentration ascorbic acid (AsA) supplementation over a long period on growth, plasma components, nonspecific immune responses, and thermal tolerance in rainbow trout Oncorhynchus mykiss. Four commercial diets supplemented with 0, 100, 1000, and 5000 mg AsA per kg of diet (designated AsA0, AsA100, AsA1000, and AsA5000, respectively) were fed to rainbow trout (initial weight 1.85 g) for 100 days. AsA contents in liver increased with increasing dietary AsA levels. Feeding period, growth performance, and plasma components did not differ significantly between the AsA groups. On the other hand, the phagocytic assay [nitro-blue tetrazolium (NBT) assay] was significantly higher in fish fed AsA1000 and AsA5000 than those fed a diet without AsA (AsA0) at the end of feeding trial. Superoxide dismutase (SOD) activity in the intestines of fish fed AsA5000 was also significantly higher than that of fish fed AsA0. In the thermal tolerance test, fish fed AsA5000 only showed significantly lower cumulative mortality compared with the AsA0 group. In conclusion, high-concentration AsA supplementation such as AsA5000 over a long period does not induce any adverse effects and can enhance disease and stress resistance in rainbow trout. © 2011 The Japanese Society of Fisheries Science. Source

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