Ayu Plecoglossus altivelis is one of the most popular fish species not only as food, but also as fishing target in Japan. “Tomozuri” is popular capture method of Ayu. “Tomozuri” is the method to catch Ayu used decoy, and this method also use the aggression of territory formed Ayu. This territory formed Ayut is required as artificial seed population for release. It is assumed that two genetic and environmental factors are affecting to the formation of territory in Ayu. But, the details of genetic control of territory formation in Ayu are unknown. In this study, genetic characteristics of recaptured Ayu by fishing and cast net were compared.
Two Ayu strains were used in this study. One is originated from Tsuruta Lake in Kagoshima Prefecture (Southern part of Japan), and the other is originated from Ani River in Akita Prefecture (Northern part of Japan). These strains have been maintained 4 to 5 generations in private farms and the seeds for release were produced at autumn in 2017, released to Oda River in Fukushima Prefecture at May, and recaptured at August in 2018. Tomoduri (Fish) and cast (Cast) were used for recapture. The individuals caught by Fish were assumed as the territory formed type, and the individuals caught by cast net were assumed as the non-territory type. Fifteen microsatellite DNA markers were used in this study. Genetic variability was measured by average heterozygosity, and population differences were compered by FST and PCA analysis.
Average heterozygosity in the Cast groups indicated higher value compared with the Fish groups in both Akita and Kagoshima strain. Cast group was indicated similar genetic characteristics between Akita and Kagoshima, and same phenomenon was observed in Fish group. PCA analysis represented it clearly (Fig.). These results suggest that the genetic convergence in Fish group and existence of genetic factors for the formation of territory in Ayu.