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147 results on '"Kawaguchi, Yoichi"'

10. At-Sea Habitat Use of Rhinoceros Auklets Breeding in the Shelf Region of Eastern Hokkaido

Author

Sato, Takahiro, Yabuhara, Yuki, Okado, Jumpei, Watanuki, Yutaka, Yamauchi, Akihiro, Kawaguchi, Yoichi, Sato, Takahiro, Yabuhara, Yuki, Okado, Jumpei, Watanuki, Yutaka, Yamauchi, Akihiro, and Kawaguchi, Yoichi

Abstract

At-sea habitat use of breeding seabirds is strongly influenced by marine environmental features that vary over space and time. The use of bio-loggers allows researchers to track fine-scale movements of seabirds and provides opportunities to identify the primary factors affecting their area use for foraging. Using GPS loggers, we tracked chick-rearing rhinoceros auklets (Cerorhinca monocerata), which are wing-propelled divers, at Daikoku Island, eastern Hokkaido, Japan. The central phase for foraging activity on birds' trips was determined using a multiple change points model. To examine environmental factors explaining the distribution of the foraging phase, a generalized additive model was used where sea surface temperature, chlorophyll a concentration, bathymetry, and distance from the colony were explanatory variables. To obtain information supporting the behavioral tracking, prey items in the bill-loads of adult auklets were collected. We found that auklets foraged over the continental shelf shallower than the 200-m isobath and that distance from the colony was related to the area use. Adult auklets predominately brought back age-0 chum salmon (Oncorhynchus keta), which was abundant in coastal waters along southeast Hokkaido during the study period. Our findings indicate that rhinoceros auklets rearing chicks, hence visiting nests frequently, on Daikoku Island can find suitable feeding grounds nearby.

Published
2022

14. Summer microhabitat partitioning by different size classes of masu salmon (Oncorhynchus masou) in habitats formed by installed large wood in a large lowland river

Author

Nagayama, Shigeya, Kawaguchi, Yoichi, Nakano, Daisuke, and Nakamura, Futoshi

Subjects
Habitat partitioning (Biology) -- Research, Pacific salmon -- Behavior, Pacific salmon -- Distribution, Pacific salmon -- Environmental aspects, Company distribution practices, Earth sciences
Abstract

Different size classes of masu salmon (Oncorhynchus masou) were partitioned in three-dimensional space in habitats created by artificially installed large wood (LW) structures in a large river. Fish >300 mm in size (L-sized) returning from the ocean distinctly occurred in sheltered areas near the riverbed, which had a moderate current velocity and contained large root wads or tree trunks; 140-200 mm (M-sized) and 100-120 mm (S-sized) fish selected deep areas of high velocity current adjacent to LW structures; [less than or equal to]80 mm fish (SS-sized) were most common in the lower depth layers throughout all LW habitats, including shallow areas with moderate currents where LW structures blocked the fast currents. Some SS-sized fish used cover areas provided by branches and leaves. Masu salmon abundance in all size classes combined was greater in habitats with LW structures than in habitats without them. Our study suggests that the natural recruitment of whole trees from the riparian zone or artificial placement of whole trees will have a profound effect on creating salmonid habitats in large rivers. Les differentes classes de taille de saumons masou (Oncorhynchus masou) se repartissent dans l'espace tridimensionnel des habitats crees par l'installation d'importantes structures de bois (LW) dans une grande riviere. Les poissons >300 mm (de taille L) qui reviennent de l'ocean se retrouvent de facon caracteristique dans les zones protegees pres du lit de la riviere qui possedent un courant moyen et de gros amas de racines ou des troncs d'arbres. Les poissons de 140-200 mm (de taille M) et de 100-120 mm (de taille S) choisissent les zones profondes a courant rapide adjacentes aux structures LW. Les poissons [less than or equal to] 80 mm (de taille SS) sont plus communs dans les couches les plus profondes dans tous les habitats de LW, mais aussi dans les zones peu profondes a courant modere ou les structures LW bloquent les courants rapides. Quelques poissons de taille SS utilisent les zones de couvert formees par les branches et les feuilles. L'abondance des saumons masou, toutes classes de taille combinees, est plus importante dans les habitats contenant des structures de LW que dans ceux qui n'en ont pas. Notre etude laisse croire que l'apport naturel d'arbres entiers provenant du rivage ou l'addition artificielle d'arbres entiers a un effet profond en creant des habitats a salmonides dans les grandes rivieres. [Traduit par la Redaction], Introduction Large wood (LW), which originates in forests and is transported into rivers, can have a significant influence on channel form (Nakamura and Swanson 1993, 1994; Montgomery et al. 2003), [...]

Published
2009

23. Time Series Changes in Fish Assemblages and Habitat Structures Caused by Partial Check Dam Removal

Author

Nagayama, Shigeya, Ishiyama, Nobuo, Seno, Taro, Kawai, Hideyuki, Kawaguchi, Yoichi, Nakano, Daisuke, Nakamura, Futoshi, Nagayama, Shigeya, Ishiyama, Nobuo, Seno, Taro, Kawai, Hideyuki, Kawaguchi, Yoichi, Nakano, Daisuke, and Nakamura, Futoshi

Abstract

Despite a steep increase in dam removal projects, there are few studies on the biophysical responses to dam removal. In this study, we evaluated the short-term (1.5 years) and long-term (5.5 years) effects of partial check dam removal on fish assemblages and their habitats. First, the habitat preferences of fish were examined at a channel unit scale: pools, rapids, and side channels satisfied the seasonal habitat requirements of the fish assemblages. Partial check dam removal increased the abundance of these habitats and diversified the habitat structures owing to the sediment release from the dam; in contrast, the bedrock distinctly decreased 1.5 years after dam removal. However, 5.5 years after dam removal, the bedrock proportion increased, and the habitat structures were simplified again owing to the re-transportation of sediments. Similar temporal changes were also determined through a reach-scale analysis with a change in the bed materials. Anadromous Oncorhynchus masou began to spawn and recolonize in the upstream section of the dam after the dam removal, causing similar assemblage compositions between the downstream and upstream sections. The abundance of Salvelinus malma and Noemacheilus barbatulus toni in the upstream reaches decreased over time after the dam removal. The temporal changes in the biophysical responses suggest that long-term monitoring is indispensable for the reliable evaluation of dam removal effects.

Published
2020

39. Ecology and Civil Engineering

Author

BABASAKI, Masahiro, primary, TAKAHIRA, Koji, additional, KAWAGUCHI, Yoichi, additional, SIMATANI, Yukihiro, additional, and ONO, Yuichi, additional

Published
2011
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42. Ecology and Civil Engineering

Author

TANAKA, Wataru, primary, KANO, Yuichi, additional, YAMASITA, Tomomi, additional, SAITOU, Kei, additional, KAWAGUCHI, Yoichi, additional, and SHIMATANI, Yukihiro, additional

Published
2011
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