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    Effects of pH and salinity on growth and survival of juvenile sea cucumber Holothuria scabra (Jaeger, 1833)
    Abagat, Christian M. (Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, 2012-03)
    Sea cucumber aquaculture could provide a solution to both enhance declining wild sea cucumber populations through restocking and provide sufficient beche-de-mer product to satisfy the increasing Asian market demand. The growth and survival of hatchery-reared Holothuria scabra juveniles at different pH-salinity levels were investigated. Juveniles were exposed for 14 days in six pH-salinity levels: Trt 1 (pH 6.5 — 6.7, 26-28 %o), Trt 2 (pH 6.5 - 6.7, normal salinity), Trt 3 (pH 7.0 - 7.2, 26-28 %o), Trt 4 (pH 7.0 — 7.2, normal salinity), Trt 5 (normal pH, 26-28 %o) and Trt 6 (normal pH, normal salinity) as the control. Multivariate analysis of variance (MANOVA) with repeated measurements revealed that pH and salinity had a significant effect on growth (length, width, and weight) and survival of H. scabra juveniles. Slight seawater desalination combined with high acidification (pH: 6.5-6.7) had lethal effects on H. scabra juveniles. While H. scabra juveniles could be reared in seawater with pH ≥ 7.0- 7.2 and salinity ≥ 26-28 %o, ambient seawater conditions remained the most suitable in rearing H. scabra juveniles for optimum growth and survival.
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    The response of Sandfish Holothuria scabra (Jaeger) juveniles to salinity and temperature changes
    Caber, Dieyna B. (University of the Philippines Visayas, 2016-02)
    Sandfish Holothuria scabra is one of the most economically valuable species of sea cucumbers. Despite being the subject of many research projects and is currently cultured commercially, many of its basic physiological aspects are not yet known or established. This study was conducted to determine the effect of salinity and temperature on the oxygen consumption rate (OCR) of sandfish juveniles. Initially, acclimation to lower salinity was compared to direct transfer. ANOVA showed that the OCR of sandfish juveniles acclimated for 30 and 120 min to 30 and 25 ppt from ambient salinity (35 ppt) were not significantly different (P>0.05) to that of sandfish directly transferred. At 8 h, the OCR values at 30 min acclimation were 0.012 ± 0.002 mgO2/L/h/g at 35 ppt, 0.019 ± 0.004 mgO2/L/h/g at 30 ppt (direct transfer), 0.015 ± 0.001 mgO2/L/h/g at 30 ppt (acclimated), 0.019 ± 0.002 mgO2/L/h/g at 25 ppt (direct transfer) and 0.013 ± 0.002 mgO2/L/h/g at 25 ppt (acclimated). At 120 min acclimation, the OCR were 0.012 ± 0.002,0.019 ± 0.004, 0.015 ± 0.000,0.019 ± 0.002, and 0.013 ± 0.001 mgO2/L/h/g, respectively. In the second part of the study, when sandfish juveniles were exposed to salinities of 35 (ambient salinity) 30 and 25 ppt and temperatures of 34,29 (ambient temperature) and 24 °C over 8 h, their OCR values fluctuated at the highest temperature and even more so at the lowest temperature. Because the experiments at different temperatures were conducted separately, the results could not be compared statistically. However, due to the degree of OCR fluctuation it appears that the sandfish juveniles were stressed at 34 °C and more stressed at 24 °C. This is supported by stress indicators observed visually during the experiment. The absence of OCR fluctuation at ambient temperature (29 °C) indicates that this is the more appropriate temperature for sandfish culture. Based on the results of the study, salinity has no effect on sandfish OCR up to 10 ppt below ambient. These results may be useful for selecting optimal conditions for growth and survival, as well as selecting optimal locations for stock enhancement purposes.