2025-05-30 京都大学
本研究の概要:(A)は本研究で対象とした両側回遊性魚類、(B)は海らしさの種間、種内変異に関する概念図
<関連情報>
- https://www.kyoto-u.ac.jp/ja/research-news/2025-05-30
- https://www.kyoto-u.ac.jp/sites/default/files/2025-05/web_2505_Tanaka-1f28ea159193200b36c0c568c3534172.pdf
- https://onlinelibrary.wiley.com/doi/10.1111/jfb.70084
両性魚類の海洋資源利用度における種間・種内変動 Inter- and intraspecific variation in the degree of marine-derived resources of amphidromous fishes
Ryosuke Tanaka, Taiga Kunishima, Kentarou Hirashima, Tamihisa Ohta, Chikage Yoshimizu, Ichiro Tayasu, Hiromi Uno, Takuya Sato
Journal of Fish Biology Published: 21 May 2025
DOI:https://doi.org/10.1111/jfb.70084
Abstract
Migratory animals often transport allochthonous materials, energy or organisms from donor to recipient ecosystems, thereby affecting the dynamics of consumers, communities and ecosystems in the recipient systems. The biomass of migrants is commonly assumed to be equal to that of the allochthonous materials they transport, with the inherent assumption that migrant bodies are produced purely from allochthonous resources. However, the extent to which the body composition of many migratory animals consists of allochthonous materials [e.g., the proportion of total body mass consisting of allochthonous resources, hereafter degree of allochthony (DOA)] may gradually decrease if the animals consume autochthonous resources during their migration. Ignoring this process leads to an overestimation of the magnitude and temporal features of material subsidies. In this study, we quantified the DOA of nine amphidromous fish species that migrate from marine to rivers, using the sulphur stable isotope (δ34S) analysis. The DOA varied substantially among species (11%–82%) and even within species (Sicyopterus japonicus had the highest DOA: 22%–97%). Species with larger body sizes tended to exhibit a lower DOA. This trend was also observed at the species level for six of the nine species, with five species showing an additional pattern of later migrating individuals with lower DOA. These results imply that quantifying DOA is important for accurately estimating material subsidies across ecosystems, owing to the upstream migration of amphidromous fish. Life-history studies of amphidromous fishes are crucial for elucidating the mechanisms behind inter- and intraspecific variation in DOA, which ultimately contributes to a better understanding of marine-river ecosystem linkages mediated by these fishes.
