Study on the protection for the endangered freshwater goby, Rhinogobius sp. BI from the Bonin Islands
2009
Yokoi, K.(Kinki Univ., Nara (Japan). School of Agriculture)
An undescribed species of the genus Rhinogobius, 'Ogasawara-Yoshinobori' (Rhinogobius sp. BI), is the only endemic species of freshwater fish in the Bonin Islands of the northwestern Pacfic Ocean. This goby is listed as an endangered species on the Red List of Japan, because there are potentially few suitable habitats for it on a limited spatial scale as a result of habitat disappearance due to river improvement, the introduction of exotic species and the decline of precipitation. Urgent practical measures to protect the natural populations of this goby are needed, but there is extremely limited biological information available of the type needed to develop effective protective measures for this fish. In this study, biological background data on this goby were accumulated, focusing on morphological, ecological, physiological and genetic information. External features and early development were studied to obtain morphological information; distribution, habitat circumstance, breeding and migration to obtain ecological information; salinity tolerance, sperm motility and cryopreservation of spermatozoa to obtain physiological information: and genetic diversity and population structure to obtain genetic information. In each chapter, I compare the biological traits of this goby, which has adapted to the oceanic island environment to those of congeners. Based on findings, I discuss two major protective approaches for this endangered goby, 'in situ conservation' and 'ex situ preservation'.
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