Ryota Kawanishi

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In lotic systems, the hyporheic zone has been suggested as a potential refuge for aquatic organisms during disturbances (hyporheic refuge hypothesis). However, the supporting evidence is unclear, especially regarding the survival of hyporheic refugees and their contribution to the recovery of post-disturbance populations. Moreover, few studies have focused(More)
We examined habitat use by spinous loach (Cobitis shikokuensis), an endangered benthic fish in Japan, in relation to distance to the stream bank, water depth, current velocity, substrate types and bed-subsurface conditions (fine-sediment volume, vertical hydraulic gradient). In the study reach (Shigenobu River in Shikoku Island), spinous loach exhibited a(More)
We examined habitat factors related to the distribution and abundance of the spinous loach Cobitis shikokuensis, an endangered benthic fish, in the Shigenobu River system, southwestern Japan. In the study river, the spinous loach was distributed widely along the main stem, from headwater to near the mouth, whereas it was rarely found in tributary streams.(More)
The mating behaviour, fecundity characteristics and egg production process were investigated in the barbed pipefish Urocampus nanus under aquarium conditions. The mating behaviour consisted of five motor patterns, some of which have been generally reported in other syngnathids. Neither the number nor size of newborns related to the size of parents, although(More)
Vertical hydrological connectivity between the surface stream and benthic and hyporheic zones plays a key ecological role in the biodiversity of lotic ecosystems because it allows surface and benthic organisms to use the hyporheic zone as a seasonal habitat and refuge. Use of the hyporheic zone by surface/benthic organisms has been well studied in(More)
—We established the experimental protocol to analyze the developmental stages of a freshwater goby, Rhinogobius flumineus. The males collected from river showed the same courtship behavior in the test tank as in the field, and the fertilized eggs attached on the plastic film were conveniently acquired. The chronological observation of embryogenesis and(More)
Cymothoid isopods (family Cymothoidae) are commonly found parasitizing diverse fishes, including commercial species. However, the effects of these parasites on host body condition are still poorly known. Here we investigated the spatial variation of the effects of parasite infection on host body condition, using the parasitic load of the cymothoid Mothocya(More)
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