Report on Distribution and Spawning of Small-scale Sillago, Sillago parvisquamis (family Sillaginidae), Based on Specimens from Yamaguchi Bay in Western Seto Inland Sea, Japan. <Article>

Abstract

瀬戸内海山口湾で2005 ～ 2008 年に,絶滅危惧種アオギスSillago parvisquamis 8 標本(SP-YB1 ～ 8)を採集した。全長226.5 ～ 320.1mm,体長197.7 ～ 281.0mm,いずれも雌で,年齢はSP-YB1 ～ 6 が1才,SP-YB7 が3才,およびSP-YB8 は4才で,全個体が2004年級であった。卵巣の組織学的検討より,SP-YB1 ～ 7 では,最も発達した正常な卵母細胞は第三次卵黄球期か胚胞移動期で,排卵後濾胞細胞を有し,活発な産卵活動が確認された。釣りCPUE(個体数/3時間/ 人)は,2005 ～ 2012年では,5 ～ 7月は0.2(n=24),通年では0.1(n=49)であった。2004年級を主な対象とした2005 ～ 2006年の2年間では,5 ～ 7月は0.3(n=14),通年では0.2(n=23)であった。今回,標本に基づき山口湾を生息地および繁殖地として記載した。Small-scale sillago, Sillago parvisquamis, were collected from Yamaguchi Bay, western Seto Inland Sea, Japan. This species has been evaluated as an endangered species in Japan. Eight specimens (sample no. SPYB1-8) collected in 2005-2008 were 226.5-320.1 mm TL, 197.7-281.0 mm SL and were all adult females. The ages of SPYB1-6, 7, and 8 were 1, 3, and 4 years, respectively, and all individuals were of the 2004 class. Judging from ovarian histological samples, the most developed stage of normal oocytes in SPYB1-7 was the tertiary yolk globule stage or the migratory nucleus stage. All individuals had a lot of post-ovulatory follicles. Therefore, these two evidences indicate spawning. The catch per unit effort (CPUE) (indiv. / 3 hours / person) by fishing in 2005-2012 was 0.2 for the spawning season (n=24) and 0.1 for the whole year (n=49). For the 2004 class, CPUE in 2005-2006 was 0.3 for the spawning season (n=14) and 0.2 for the whole year (n=23). This is the detailed report of the distribution and spawning of Sillago parvisquamis based on specimens from Yamaguchi Bay