Browsing by Author "Ishimatsu, A."

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    Effects of Elevated Carbon Dioxide and Temperature on Survival and Morphology of Japanese Whiting Sillago Japonica
    (2016) Yona, G.; Madalla, Nazael; Mwandya, Augustine W.; Ishimatsu, A.; Bwathondi, Philip O. J.
    The objective of the present study was to examine the effect of elevated CO2 and temperature on survival and morphology of Sillago japonica yolk sac larvae under the Institute for East China Sea Research (ECSER) Nagasaki, Japan. In this study, we examined hatching success, survival and morphology of the larvae of Sillago japonica under four conditions: control (C), seawater pCO2 382µatm, temperature 27 °C; high CO2 (HC), 915µatm, 27 °C; high temperature (HT), 385 µatm, 31 o C; and high CO2+high temperature (HCT), 932µatm, 31 o C. Fertilized eggs were obtained from broodstock reared in natural seawater, and transferred to experimental containers in each treatment. Hatched larvae were observed until the completion of yolk sac absorptions on 3 days post hatching (dph). The experiment was repeated four times with 4 replicates for each treatment in each experiment. Also, the temperature appeared to have exerted a stronger influence on hatching success (Hs) and larval survival (Sv): Hs and Sv at 3 dph were both significantly (p>0.05) depressed in HT (Hs 52.5±1.25%, Sv 23.8±4.38%) and HCT (Hs 51.3±3.13%, Sv 20.0±0.63%) treatments than in C (Hs 98.1±0.94%, Sv 74.4±2.03%) and HC (Hs 95.0±2.5%, Sv 49.7±3.44%) treatments. In contrast, CO2 was the predominant factor responsible for morphological abnormality: percentage morphological abnormality was significantly (p>0.05) higher in HC (15.8±2.72%) and HCT (41.0±10.86%) treatments than in C (0.4±0.65%) and HT (2.4±2.40%) treatments. Most individuals in HC and HCT treatments had body axis either curved or bent, with aberrant swimming behavior. These results indicate that projected future ocean environments will have significant negative impacts on hatching success, and larval survival and morphology of S. japonica, which might have serious ramifications for recruitment of the species. Comparative studies on other teleost and elasmobranch species are critically needed.