Gifu Prefectural Research Institute for Fisheries and Aquatic Environments

Kakamigahara, Japan

Gifu Prefectural Research Institute for Fisheries and Aquatic Environments

Kakamigahara, Japan
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Shigeta K.,Ryukoku University | Tsuma S.,Gifu Prefectural Research Institute for Fisheries and Aquatic Environments | Yonekura R.,Gifu Prefectural Research Institute for Fisheries and Aquatic Environments | Kakamu H.,Gifu Prefectural Research Institute for Fisheries and Aquatic Environments | Maruyama A.,Ryukoku University
Ecological Research | Year: 2017

Although stable isotope analysis is a powerful tool for determining animal diets, migration patterns, and the structure of food webs in aquatic systems, the slow response of isotopic ratios in the traditionally used muscle tissue of fishes often hampers this approach. By analyzing tissues with more rapid isotopic change, this technique can be used over a finer time scale than traditional isotopic analyses. We conducted a diet-switch experiment to compare changes in the stable carbon and nitrogen isotope ratio values (δ13C and δ15N, respectively) in epidermal mucus, fin and muscle tissues of three species of freshwater cyprinid fishes. The half-life of the isotopic change ranged from 62 to 144 days in mucus, 57 to 202 days in fin, and 196 to 680 days in the muscle tissue. The isotope ratios in mucus changed more rapidly than those in muscle tissues in the three species examined, similarly to the previously studied three species (catfish, steelhead, freshwater goby), whereas fin showed relatively variable trends in isotopic change. Interspecific variation in the trophic discrimination factor (TDF) was particularly large in the δ13C values of fin tissue compared with those in the other two tissues. With generally rapid change and relatively invariable TDF, the use of epidermal mucus in isotope analysis instead of the widely used fin and muscle tissues is advantageous for studying short-term changes in food habits of fishes and food web structures. © 2017 The Ecological Society of Japan


Yamazawa H.,Tokai Gakuin University | Kuwada T.,Gifu Prefectural Research Institute for Fisheries and Aquatic Environments | Yamazawa K.,Tokai Gakuin University | Yamazawa K.,Nagoya Women's University | And 2 more authors.
Nippon Shokuhin Kagaku Kogaku Kaishi | Year: 2015

An artificial diet mixed with persimmon wine residue (PR) was used in cultivating ayu fish in an effort to improve its taste and body color, and for the effective use of leftover PR. There were no significant differences in the fatty acid composition of dorsal meat between PR-feeding and control groups. Measurement of color differences in yellow spots, dorsal fins, ventral fins, and caudal fins revealed that body color of the PR-feeding group was significantly improved compared to the control group. A survey was administered regarding ayu overall, and the survey items "appearance" and "taste" were rated significantly higher in the PR-feeding group than in the control group. From the above mentioned results, it is suggested that as an effective use for PR, a PR-mixed feed can improve preferential attributes of ayu such as body color and taste.


Koya Y.,Gifu University | Fujii R.,Gifu Prefectural Research Institute for Fisheries and Aquatic Environments | Yambe H.,Tokyo University of Agriculture | Tahara D.,Fukui Prefectural University
Ichthyological Research | Year: 2015

Although renal hypertrophy during the reproductive period has been reported previously in species of Cottus, the function of the kidney in reproduction remains unknown. In order to clarify the role of the kidney in reproduction, seasonal changes in gonad and kidney weight, serum androgen levels, kidney histology, and the protein content of urine, were examined in the small-egged Kajika, Cottuspollux SE sensu Yokoyama and Goto (2005). Compared to the non-reproductive period (August), renal hypertrophy of male fish during the reproductive period (December) was equivalent to a twofold increase in kidney-somatic index values. A marked increase in epithelial cell height in the proximal convoluted tubule (PT) was correlated with elevated serum 11-ketotestosterone levels, suggesting that total kidney weight increased from the non-reproductive to the reproductive period. Periodic acid-Schiff (PAS)-positive granules containing polysaccharides were observed in the cytoplasm of PT epithelia during the reproductive period. Urine retained in the urinary bladders of males exhibiting nesting behavior contained glycoproteins and low-molecular-weight substances containing polysaccharides during the reproductive period. We discussed the role of the kidney and kidney secretions in nesting male species of Cottus. © 2015 The Ichthyological Society of Japan


Koya Y.,Gifu University | Fujii R.,Gifu Prefectural Research Institute for Fisheries and Aquatic Environments | Yambe H.,Tokyo University of Agriculture | Tahara D.,Fukui Prefectural University
Ichthyological Research | Year: 2015

We found that male small-egged Kajika, Cottuspollux SE sensu Yokoyama and Goto (2005), retained a large volume of urine (approximately, 1 % body weight) in their urinary bladder while nesting under spawning substrate. This increase in urine volume occurred three days after the males were transferred to the nesting tank. Serum 11-ketotestosterone (11-KT) concentrations of males also increased approximately twofold after the males were transferred to the nesting tank. While this increase in the urinary volume was observed only during the reproductive period (late December), the increase in serum 11-KT concentration from the basal levels associated with nesting occurred from the spermatogenic period (from October to mid-December) to the reproductive period (late December). These findings suggest that the urine of nesting males plays a role in reproduction, whereas the increase in serum 11-KT levels may be associated with social status/dominance. The increased urine due to nesting contained an approximately sixfold level of 11-KT compared to the initial control values, suggesting that the urine of nesting male Kajika may have functioned as social signals to females and/or to other males. © 2015 The Ichthyological Society of Japan


Yamazaki Y.,University of Toyama | Ikeya K.,Gifu World Fresh Water Aquarium | Goto K.,Gifu Prefectural Research Institute for Fisheries and Aquatic Environments | Chimura Y.,Hekinan Seaside Aquarium
Ichthyological Research | Year: 2016

To conserve endangered species, the maintenance of ex situ captive populations with sustainable genetic diversity is often required, in combination with population viability analysis (PVA). Since 2010, the threatened Itasenpara bitterling Acheilognathus longipinnis lineages in the Kiso region, Japan, have been maintained in ex situ rearing facilities to allow for conservation efforts. In this study, we obtained microsatellite data from DNA extracted from these captive populations to elucidate their genetic diversity and effective population size. The populations of several initial generations indicated a deviation from Hardy–Weinberg equilibrium, probably due to the limited number of extracted founder individuals analyzed. The effective population size of the captive population tended to increase over the course of generations, although the degree of genetic diversity tended to decrease highlighting the concern for the progression of inbreeding. Our prediction based on the PVA suggests that the maintenance of the captive population under the current conditions could lead to extinction of the Itasenpara bitterling in 50 years. In contrast, simultaneously increasing the carrying capacity and individual exchange among populations appears to enhance the effective management of captive Itasenpara bitterling populations. © 2016 The Ichthyological Society of Japan


Kuwada T.,Gifu Prefectural Research Institute for Fisheries and Aquatic Environments | Tokuhara T.,Gifu Prefectural Research Institute for Freshwater Fish and Aquatic Environments | Shimizu M.,Hokkaido University | Yoshizaki G.,Tokyo University of Marine Science and Technology
Fisheries Science | Year: 2016

The present study retrospectively examined relationships between growth trajectory and smolting in order to identify the key regulators in commencement of smolting using groups of all-female homozygous clonal amago salmon. We found that (1) regardless of specific growth rate, the majority of fish above the threshold size (12–13 g) by the end of the decision window (early fall) became smolt in the future; (2) even if fish smaller than the threshold size during the decision window exceeded that size afterwards, they were not recruited to smolt; (3) smolting of fish that attained sufficient size during the decision window could not be suppressed by subsequent restriction of growth rate; (4) smaller fish that had not attained the threshold size during the decision window could not smoltify, even though they showed faster growth rates than that of future smolt during/after the decision window. Taken together, these findings indicated that fish mass by the end of the decision window was responsible for the determination of whether individual amago salmon could smoltify or not and that the faster growth rates observed in future smolt after the decision window occurred as a result of commitment of smoltification. © 2015, Japanese Society of Fisheries Science.

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