The First Record of the Spawning Run of Masu Salmon Oncorhynchus masou Introduced into the Patagonian Lake General Carrera, Southern Chile

Abstract

Masu salmon fry Oncorhynchus mason of two different origins, Chilean stock (MC) of 7.0g size parr and Japanese stock (MJ) of 4.9g size parr, were released in February 1987 and in October 1987, respectively, into a tributary of Lake General Carrera in Chilean Patagonia. The spawning run of the salmon (299 females and 276 males) was observed in the river from March to April 1989. The sex ratio (males per female) was regarded as nearly 1.0, and this suggested that river-resident precocious males were very scarce in the river. Mean fork lengths and weights of spawners were 56.3cm and 1, 715g, respectively. The rate of return was estimated as 1.07% for MC and 0.95 for MJ. No difference between either rate was observed though they were released at different sizes and times. Eyed-stage eggs and alevins were found in the river after the spawning season. These indicated that there is a high possibility of population establishment in the lake by the small parr release of masu salmon.