Full text loading...
Zoological Science
- Previous Article
- Table of Contents
- Next Article
Abstract
The Sanriku-ria coast of Japan, a homing area for chum salmon, Oncorhynchus keta, is characterized by a large number of small closed bays into which one or multiple short rivers flow. The present behavioral investigation of chum salmon in this region was designed to gain deeper insight into the migration of chum salmon to their natal rivers. Eighty-three fish caught at the middle part of Otsuchi Bay were tracked using an acoustic transmitter in the narrow inlet into which flow three rivers: the Otsuchi, Koduchi, and Unosumai. The majority of 18 fish that entered the Unosumai River, which flows into the southwest side of the bay, directly approached the river along the southern coast. More than half of fish that entered the Otsuchi and Koduchi Rivers, which flow into the northwest side, also migrated into the inner bay via the southerly route, and then entered these rivers frequently after passing the mouth of the Unosumai River. In the inner bay, the salinity of sea surface water suggested that water from the three rivers circulates in a counterclockwise direction at a depth of less than 1.0 m, flowing eastwardly along the southern coast. The observed migratory paths of homing salmon in Otsuchi Bay thus correspond well with the counterflow of surface river water in the bay. The present results suggest that homing migration of salmon in the Sanriku narrow inlet is guided by natal river flows.
We thank Shin-Otsuchi fishery guide for capturing homing chum salmon and their great support. We thank the Iwate Fisheries Technology Center and other fishery guides for recapturing the tagged fish, Drs. Syuichi Abe and Hideki Fukuda for valuable comments and support, and the staff of the International Coastal Marine Research Center and The University of Tokyo for technical support. We thank Prof. Christopher A. Loretz of State University of New York at Buffalo for critical reading of the manuscript. This study was supported in part by Tohoku Ecosystem-Associated Marine Science (TEAMS) research program of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the program ‘Bio-logging Science of The University of Tokyo (UTBLS), and a Grant-in-Aid for Challenging Exploratory Research from Japan Society for the Promotion of Science (JSPS) to S. N. (25660153).
Data & Media loading...