| Summary: | 碩士 === 國立中山大學 === 海洋生物研究所 === 101 === The teleost family Sciaenidae is well known for vocalization during the spawning season. Most of them live in marine and esturies, but some are restricted to freshwater environment. The difference of sound between marine and freshwater species has seldom been discussed. In this study, Boesmania microlepis, the only freshwater species occurs in Indo-west Pacific was chosen to analyze its sound characteristics, diel vocal activity and to the former compare with that of marine species. According to local people in Thailand, there is a sympatric with B. microlepis sciaenid that seemed to be different species from B. microlepis with golden hue on its body. The genetic difference between the two species was deciphered. The sounds of captive B. microlepis vocalization in cement tanks were recorded for three evenings. The sounds in the field were also recorded and analyzed. The sonic muscle and swimbladder structure of the two “species” were examined. The recordings showed a clear diel activity with a peak after the sunset. The average length of sound in B. microlepis was 125.7ms and comprised a train of pulses with a mean of 15 pulses. The dominant frequency is 1610.6 Hz, which is higher than the big-snout croaker and other marine species. The phylogenetic tree inferred from COI gene showed B. microlepis and the golden sciaenid are different species with nearly 10% of genetic variation. The dissection showed sexual dimorphism of the sonic muscle of B. microlepis with only the male possessing it. Some soniferous features were considered adaptive to freshwater environment.
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