Abstract
Southern Asian Dolly Varden Charr, Salvelinus curilus (syn. S. malma krascheninnikovi), is a salmonid fish and distributed in northeastern Asia. Rishiri Island represents the northern edge of the distribution range for the charr in Japan, and several studies have reported their presence. However, no basic ecological information, such as body size distribution and population densities, have been reported for the charr population of Rishiri Island.
In this paper, Genki Sahashi and Kentaro Morita report the body size distribution and populatiuon density of the Southern Asian Dolly varden charr in the Higashi-Nodottomari River on Rishiri Island and review previous reports regarding the charr on Rishiri Island. In the Higashi-Nodottomari River, 76 immature individuals, 12 mature males, and 5 mature females were collected. The fork length distribution showed a multi-modal distribution, and the smallest size group (ranging from 40-70 m) is considered to represent age 0+ years. The estimated population density was 0.37 ind./m2.
Based on the literature survey, collection records reporting the charr were confirmed in five rivers on Rishiri Island. In the Higashi-Nodottomari River, colletcion records of the charr dated back to 1947, before the hatchery transplantation of salmonid. in addition, Yamamoto et al. (2020) reported that the Southern Asian Dolly Vardan charr collected from the Higashi-Nodottomari River had a unique haplotype that was not found in the fish collected from rivers om Hokkaido or Skhalin islands. These findings suggested that the Higashi-Nodottomari River represents a natural distribution area for this species.
Read full article.