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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


Castano-Sanchez C.,Tokyo University of Marine Science and Technology | Fuji K.,Tokyo University of Marine Science and Technology | Ozaki A.,Tokyo University of Marine Science and Technology | Ozaki A.,Japan National Research Institute of Fisheries And Environment of Inland Sea | And 12 more authors.
BMC Genomics | Year: 2010

Background: Japanese flounder (Paralichthys olivaceus) is one of the most economically important marine species in Northeast Asia. Information on genetic markers associated with quantitative trait loci (QTL) can be used in breeding programs to identify and select individuals carrying desired traits. Commercial production of Japanese flounder could be increased by developing disease-resistant fish and improving commercially important traits. Previous maps have been constructed with AFLP markers and a limited number of microsatellite markers. In this study, improved genetic linkage maps are presented. In contrast with previous studies, these maps were built mainly with a large number of codominant markers so they can potentially be used to analyze different families and populations.Results: Sex-specific genetic linkage maps were constructed for the Japanese flounder including a total of 1,375 markers [1,268 microsatellites, 105 single nucleotide polymorphisms (SNPs) and two genes]; 1,167 markers are linked to the male map and 1,067 markers are linked to the female map. The lengths of the male and female maps are 1,147.7 cM and 833.8 cM, respectively. Based on estimations of map lengths, the female and male maps covered 79 and 82% of the genome, respectively. Recombination ratio in the new maps revealed F:M of 1:0.7. All linkage groups in the maps presented large differences in the location of sex-specific recombination hot-spots.Conclusions: The improved genetic linkage maps are very useful for QTL analyses and marker-assisted selection (MAS) breeding programs for economically important traits in Japanese flounder. In addition, SNP flanking sequences were blasted against Tetraodon nigroviridis (puffer fish) and Danio rerio (zebrafish), and synteny analysis has been carried out. The ability to detect synteny among species or genera based on homology analysis of SNP flanking sequences may provide opportunities to complement initial QTL experiments with candidate gene approaches from homologous chromosomal locations identified in related model organisms. © 2010 Castaño-Sánchez et al; licensee BioMed Central Ltd. Source


Namiki S.,University of Tokyo | Tanaka H.,Seikai National Fisheries Research Institute | Katayama S.,Japan National Research Institute of Fisheries Science | Funaki O.,Kanagawa Prefectural Fisheries Technology Center | And 2 more authors.
Fisheries Science | Year: 2010

In order to validate daily increment formation in otoliths of immature and adult Japanese anchovy Engraulis japonicus, three rearing experiments using chemical marking of otoliths were conducted on adult anchovy in summer 2004 and immature anchovy in summer 2005 and in winter 2006. In the two experiments conducted in summer, the number of otolith microincrements between alizarin complexone (ALC) marks showed that microincrements were formed daily. In the summer 2005 experiment, immature anchovy under conditions of reduced daily food rations also showed daily microincrement formation. Average increment width was 0.9 μm in adults and 1.8-3.1 μm in immature anchovy. In contrast, no clear increments were observed between ALC marks on the otoliths from the experiment in winter 2006, and scanning electron microscope (SEM) observations failed to confirm clear increment formation. We consider that low water temperatures (<13-14°C) restricted otolith growth and lowered the contrast between the discontinuous and the incremental zones of the otolith increments. For age estimation of Japanese anchovy, clear increments wider than about 1 μm in the otolith can be regarded as daily increments. However, daily age estimation of immature and adult anchovy that experience low water temperatures in winter may be difficult due to the obscurity of the increments. © 2010 The Japanese Society of Fisheries Science. Source


Katano O.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Natsumeda T.,Chiba Institute of Science | Natsumeda T.,Ibaraki University | Suguro N.,Kanagawa Prefectural Fisheries Technology Center
Ecological Research | Year: 2013

Mechanisms that determine the strength of trophic cascades from fish to benthic algae via algivorous invertebrates in stream communities have not been clarified. Using seven fish species, we tested the hypothesis that the interspecific variation of predatory behavior of fishes affects the strength of trophic cascades in experimental streams. One or two species of fish were introduced into flow-through pools of 2.5 m2 and the abundances of benthic invertebrates and algae were monitored. Pike gudgeon, a diurnal benthic feeder, triggered a strong trophic cascade but masu salmon, a diurnal drift feeder, did not have a cascading effect. Japanese dace, which is both a diurnal benthic and drift feeder, increased the algal biomass, but the nocturnal benthic feeder cut-tailed bullhead had little cascading effect. The diurnal benthic feeder silver crucian carp also had a cascading effect, but no trophic cascade was triggered either by Asian pond loach or by Japanese common catfish, both of which are nocturnal benthic feeders. Thus, diurnal benthic fish exerted a stronger cascading effect than diurnal drift feeders or nocturnal fish. The combination of two fish species enhanced the per-capita strength of trophic cascades, probably because one of the two species, the benthic feeder, preyed on more invertebrates than in the single-species pools. © 2013 The Ecological Society of Japan. Source


Kodama K.,Japan National Institute of Environmental Studies | Tajima Y.,Kanagawa Prefectural Fisheries Technology Center | Shimizu T.,Kanagawa Prefectural Fisheries Technology Center | Ohata S.,Chiba Prefectural Fisheries Research Center | And 2 more authors.
Marine Pollution Bulletin | Year: 2014

We investigated effects of severe hypoxia (dissolved oxygen <1 mll-1) on recruitment of mantis shrimp Oratosquilla oratoria in Tokyo Bay. Ten-year field surveys were conducted to examine quantitative relationships in annual mean densities of larvae and juveniles, and spatial distribution of juveniles and severe hypoxia. There was no significant correlation between annual mean densities of larvae and juveniles, suggesting that mortality during larval or juvenile stages varies among years, which might have regulated abundance of young-of-the-year juveniles. Juvenile density was low in the severely hypoxic area, implying that hypoxia could affect survivals and spatial distribution of juveniles. Meanwhile, there are yearly fluctuations in juvenile density in normoxic areas of both northern and southern part of the bay. This evidence suggests that abundance of post-settled juveniles might have been determined by not only effects of hypoxia, but also other factors influencing mortality during the early life stages. © 2014 Elsevier Ltd. Source

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