Abstract
A spawning redd of the salmonid fish was found in the Nigorimizu-sawa of the Oirase River system (40° 41'N, 139°58'E), which flows into the Japan Sea in Aomori Prefecture (Figs.2, 3).More than 1, 700 eyed eggs were obtained on November 21, 1960, from this redd.These eggs measured 5.3-5.9mm in diameter.They began to hatch on November 24.The alevins and fry are described and illustrated in this paper (Fig. 4).The fry, liberated in a small pond (ca.4 m2, 50-80 cm deep), took mainly small crustacea and aquatic larvae of insects and attained 38 43 mm in total length by the next April.These fry are considered as members of either of the genera Salvelinus or Hucho for their characteristic arrangement of the vomer and palatine in the roof of the mouth (Fig.5).Because the fish of Hucho is a vernal spawner in Japan, the present fry must belong to Salvelinus.
In the Nigorimizu-sawa, there are two types of char Salvelinus leucomaenis (Pallas), i.e., an anadaomous form and a fluvial dwarf form of the same species.Generally, the former grows up 40 cm or more in total length, however, the latter attains 30 cmat largest and rarely deposits eggs exceeding 300 in number at a single spawning redd.Therefore, the present spawning redd, eggs, alevins, and fry are thought to be of theanadromous char called“Amemasu”in Japanese (Fig.1).The parr marks appear inthe alevins of S.malma (Walbaum) (Blackett, 1968), but not visible in the presentalevins throughout their yolk consuming stage (Fig.4).So, there is no reason toidentify these alevins as S.malma.
