Recruitment of amphidromous sleepers Eleotris acanthopoma, Eleotris melanosoma, and Eleotris fusca into the Teima River, Okinawa Island |
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Authors: | Ken Maeda 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 & 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: | Recruitment courses of three amphidromous sleeper species, Eleotris acanthopoma, E. melanosoma, and E. fusca, were investigated at the surf zone adjacent to the river mouth and at five stations in the Teima River on Okinawa Island,
Japan. All three species occurred at the surf zone as pelagic larvae with transparent and compressed body, a conspicuous air
bladder, and an emarginated caudal fin. Eleotris fusca (16.0–19.6 mm in standard length: SL) sometimes possessed a vestige of the larval chin barbel and were larger than E. acanthopoma (9.7–13.2 mm SL) and E. melanosoma (11.2–12.8 mm SL). The pelagic larvae were also collected during full tide from the lower reaches of the tidally influenced
area of the river. The pelagic larvae may be carried in and out of the estuary with some tidal fluxes, and they may settle
when they reach the upper tidally influenced area where the salinity becomes extremely low. Body width and pigmentation of
newly settled larvae increased. E. fusca was considered to migrate upstream to the freshwater area against the flow of the river just after reaching the settled stage.
After settlement, all three species became completely pigmented, the caudal fin became round in shape, and the fin ray counts
became complete with growth. Also, E. acanthopoma dispersed widely to the lower part of the tidally influenced area or to the lower reaches of the freshwater area, E. melanosoma dispersed to the lower part of the tidally influenced area, and E. fusca dispersed upstream. |
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Keywords: | Eleotris Larva Recruitment Surf zone Amphidromy |
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