The maturity and breeding season of the bellybarred pipefish, <Emphasis Type="Italic">Hippichthys spicifer</Emphasis>, in Okinawa-jima Island rivers |
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Authors: | Taiki Ishihara Katsunori Tachihara |
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Institution: | (1) Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara-cho, Nakagami-gun Okinawa, 903-0213, Japan;(2) Laboratory of Fisheries Biology and Coral Reef Studies, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara-cho, Nakagami-gun Okinawa, 903-0213, Japan |
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Abstract: | We investigated the breeding season and size at maturation and described the morphology of newly released Hippichthys spicifer larvae collected from the estuaries of four rivers on northern Okinawa-jima Island, southern Japan. The minimum size of brooding
males was 108 mm standard length (SL). The smallest mature female, as estimated from gonadosomatic index (GSI) analysis and
histological observations of gonads, was about 100 mm SL. Histological observations showed the gonad of H. spicifer to be a cylindrical tube with a sequential pattern of follicle development and a single germinal ridge. We surmised that
the breeding season is year-round, as shown by monthly changes in female GSI, gonad histology, and monthly changes in the
occurrence of brooding males. The monthly changes in female GSI and proportions of brooding males were small in winter. The
number of eggs in the male brood pouch ranged from 114 to 1,764 (604.4 ± 322.8, mean ± standard deviation; n = 25). The SL of the released larvae was 9.9 mm. All fins except the pectoral fins were formed, the body was elongated, and
the developmental stage was similar to that of other Urophori species. The smallest individual present in the mangrove areas
of estuaries was 78.0 mm SL. |
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