Unauthorized Stocking of an Endangered Bitterling Acheilognathus typus in an Irrigation Pond Detected and Substantiated by Biological and Human Lines of Evidence

Abstract

Acheilognathus typus, an endangered bitterling, was captured in an irrigation pond in the northern part of Niigata prefecture, Japan, in 2019. This bitterling species had once occupied that region. Its absence for years indicated the possible extinction of the bitterling there. We expected that the recently captured individuals are an unknown remnant stock of that endangered species found through an extensive survey. Mitochondrial genotyping, however, revealed that the recently captured individuals had a common haplotype with those from Kashimadai, Miyagi prefecture, Japan. The uniqueness of the haplotype to these two ponds indicates a stock identity between them. In the pond in Kashimadai, the illegal activity of catching the bitterlings by a person from the northern Niigata prefecture was detected in 2015. We conclude that the bitterling from the northern Niigata prefecture was stocked from a pond in Kashimadai. Our report is the first example of unauthorized bitterling stocking substantiated from both biological and human lines of evidence.