Population estimation of Kunimasu <i>Oncorhynchus kawamurae</i> in Lake Saiko

Abstract

In Lake Saiko, Kunimasu Oncorhynchus kawamurae was discovered and has been caught by recreational angling indistinguishable from a related species Himemasu Oncorhynchus nerka. From 2012 to 2014, we conducted a creel survey for two days just after the start of the angling season, aging by scale, and species identiˆcation by DNA analysis. The total length composition was transformed into the age composition using age-length keys. Under the assumption of an equilibrium condition, total mortality Z was roughly estimated from the age composition.Fishing mortality F was estimated from Z by subtracting natural mortality empirically estimated from longevity (four to seven years). The populations of Kunimasu and Himemasu were estimated by the number of total catch C, F, and Z. Multiplying N and the ratio of the number of Kunimasu in the recreational catch, the population of Kunimasu was roughly estimated to be 4,300 11,000 individuals.