Nagaremon-charr, a rare morphotype of Salvelinus leucomaenis characterized by wavy parr markings (Nagaremon type) instead of typical parr marks (normal type), inhabit a tributary of the Ane River basin (Lake Biwa system). However, the frequency of the Nagaremon type has decreased from the 1970s. To explain this reduction, mating trials were conducted between the Nagaremon and normal morphotypes. One trial yielded populations that approximated a 1:1 segregation ratio for the two phenotypes, suggesting that the Nagaremon type is a recessive trait and that the parent with a normal phenotype (collected from the tributary) was a heterozygous carrier for the Nagaremon trait. Therefore, conservation of Nagaremon-charr should involve management of the entire tributary, thereby including normal type charr.
