Kazushi Miyashita

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Microchemical analysis of the strontium (Sr) and calcium (Ca) ratios of otoliths was conducted to determine the life history and migration of anadromous Sakhalin taimen, Hucho perryi. In 2008 and 2009, 10 specimens were sampled from Lake Akkeshi in eastern Hokkaido, Japan. Our results indicated that some specimens migrated to brackish waters during their(More)
The Japanese Pacific walleye pollock (Theragra chalcogramma) stock is the largest stock of this species in Japanese waters. It is a key component of the Oyashio ecosystem. In southern Hokkaido waters, these fish spawn mainly during January and February near the mouth of Funka Bay (FB), and most eggs and larvae are transported into FB. During midsummer(More)
Recent studies in streams and ponds have demonstrated that the distribution and biomass of aquatic organisms can be estimated by detection and quantification of environmental DNA (eDNA). In more open systems such as seas, it is not evident whether eDNA can represent the distribution and biomass of aquatic organisms because various environmental factors(More)
The southwestern Pacific coast of Hokkaido is the main spawning ground for the Japanese Pacific stock of walleye pollock Theragra chalcogramma. A commercial gillnet fishery targeting spawning adult pollock in this area mainly operates from October to January to coincide with the migration of adult pollock from the feeding ground. Given the results of(More)
We examined factors affecting the vertical distribution of juvenile walleye pollock during “the second critical period” (i.e. the transition period of prey size) in and around Funka Bay, Hokkaido, Japan. During the day, small juveniles (<30 mm) were distributed mainly in shallow, warm, and low-salinity water within the bay, whereas larger ones (≥30 mm)(More)
Acoustic tags were used to examine the spatial and temporal distribution of southern bluefin tuna (SBT) in southern Western Australia, which is in a region where fishery-independent acoustic surveys of the recruitment abundance index of SBT have been historically undertaken. We investigated patterns of SBT distribution within and inshore of the acoustic(More)
Variations in trawl dimension, bottom contact, and catch with differing warp lengths during walleye pollock surveys conducted by the Fisheries Research Agency were examined. The ratio of warp length to fishing depth (scope ratio) was set at 2.5, 3.0 and 3.5 at depths of 110 m. At tact the bottom. Footgear contact was complete when the scope ratio was 3.0 or(More)
The swimming angle of larval Japanese anchovy (Engraulis japonicus) was measured in a tank, and target strength (TS) was calculated using a theoretical scattering model. The mean swimming angle was 12.8° (SD ±22.1). Increased speeds of flow led to increased mean swimming angles. The mean swimming angle at flow of 5 cm s−1 was higher than at other speeds. TS(More)
The behavior of endangered adult Sakhalin taimen Parahucho perryi was tracked during 2008–2010 using acoustic telemetry in the Bekanbeushi River system, which flows through eastern Hokkaido, Japan. Movement distances per unit time of tracked P. perryi were compared between mid- and downstream habitats. Results indicated that movement distances were(More)
Sustainable management of the kelp forests of the Shiretoko Peninsula, a World Natural Heritage site, is necessary due to kelp’s ecological and economic importance. The objectives of this study were to estimate the area of kelp forests and to clarify their spatial characteristics in coastal waters of the Shiretoko Peninsula. Data on the presence/absence and(More)