Relationship between <i>Edwardsiella ictaluri</i> infection and vulnerability to <i>tomozuri</i> angling in ayu

Abstract

(2017 年 9 月 27 日受付，2017 年 12 月 28 日受理，2018 年 5 月 15 日 J STAGE 早期公開) 0404, 4 South-Nakagawa Fisheries Cooperation, Nasukarasuyama, Tochigi 321 0611, JapanWe studied the frequency of Edwardsiella ictaluri carriers by polymerase chain reaction-based investigation on 879 ayu Plecoglossus altivelis caught by tomozuri angling and casting net in the Naka River from July to September 2016. As a result, the E. ictaluri positive rate increased with increasing weekly mean water temperature. The maximum positive rate was recorded in the week (31 July 6 August) when the weekly mean water temperature was over 25°C. In that week, the positive rate was 20.4 (11/54 individuals) in theˆsh caught by casting net, whereas the rate was 0 (0/36 individuals) in theˆsh caught by angling. In addition, catch per unit eŠort (CPUE) of the angling decreased with increasing daily mean water temperature. These results suggest that ayu are more vulnerable to E. ictaluri infection during the high-water temperature season and E. ictaluri infection can decrease the tomozuri angling catch.