Optimum low salinity to reduce cannibalism and improve survival of the larvae of freshwater African catfish Clarias gariepinus
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The freshwater African catfish Clarias gariepinus is carnivorous and cannibalistic even during the larval and juvenile stages and this behavior causes economic losses in aquaculture. This study examined for the first time the effect of salinity on cannibalism, survival, and growth of African catfish larvae in the hatchery. Larvae (4 days old, median 7.8 mm TL, 2.8 mg BW) of the African catfish were reared for 21 days at nominal salinity 0, 1, 2, 3, 4, 5, 6, and 7 ppt. After 21 days, they grew to 10–39 mm (median 22 mm) and 10–490 mg (median 90 mg), with no significant difference by salinity treatments. Survival ratios were similarly low (24–31%) at 0, 1, 3, and 7 ppt and significantly higher (49–55%) at 2, 4, 5, and 6 ppt. Cannibalism was significantly lower, 15–30% at 4–6 ppt, than the 40–50% at 0–3 and 7 ppt. Size variation was lower at 4–6 ppt and higher at 0–3 and 7 ppt. We recommend hatchery rearing of African catfish at the optimum low salinity of 4–6 ppt rather than in full fresh water at least up to 21 days. This rearing method fosters larval welfare and improves hatchery production.
CitationKawamura, G., Bagarinao, T., Yong, A. S. K., Sao, P. W., Lim, L. S., & Senoo, S. (2017). Optimum low salinity to reduce cannibalism and improve survival of the larvae of freshwater African catfish Clarias gariepinus.
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Growth response of Nile tilapia fry to salinity stress in the presence of an ‘internal reference’ fish Growth of three strains of Oreochromis niloticus L. fry exposed to salinity stress in the presence of an internal reference fish were compared. The Central Luzon State University (CLSU) strain was obtained from the Freshwater Aquaculture Center, CLSU, Philippines. The ISRAEL strain was acquired from the Philippine government's Bureau of Fisheries and Aquatic Resources National Freshwater Fisheries Technology Center (BFAR-NFFTC), Munoz, Nueva Ecija. The National Inland Fisheries Institute (NIFI) strain was obtained from the NIFI, Bangkok, Thailand. Eight to nine full-sib families (replicates) per strain were split into two groups. One group was grown in freshwater for 2 weeks, acclimated to 32 ppt and reared for 2 weeks and finally grown in freshwater for another 2 weeks. Another group was contemporaneously grown in freshwater polyethylene tanks for 6 weeks. Each replicate family included a size-matched internal reference population of red tilapia strain. Two-way analysis of variance (anova) revealed no significant strain differences (P=0.081; r2=0.106). However, analysis of covariance with the internal reference strain used as a covariate showed significant (P=0.049; r2=0.638) strain effects on specific growth (based on standard length measurements). The ISRAEL strain showed consistently better growth rate in both saline and freshwater environments than the NIFI and CLSU strains. We estimated the statistical power of the two-way anova (ϕ=√(k′−1)(factor MS−s2)/(k′s>2); Zar 1984) to be ∼0.30. There was a 70% probability of a Type II error and no true difference in the growth of the three strains was detected. The use of internal reference strain as a covariate improved the r2 from 0.106 to 0.638 and increased the efficiency of the test in detecting a true difference. Other strain comparison studies in our laboratory at the Southeast Asian Fisheries Development Center Aquaculture Department showed that the ISRAEL strain shows better growth than the NIFI and CLSU strains in a crowding stress tolerance experiment, when fed only with rice bran and under restrictive feeding regimes.
ArticleJRH Maquirang, RD Caturao, JH Maquirang & FL Pedroso -
IAMURE International Journal of Ecology and Conservation, 2013 - IAMURE Multidisciplinary ResearchThe study was conducted to determine the optimum salinity levels (24 ppt, 28 ppt, 32 ppt, 36 ppt and 40 ppt) for the survival and settlement rates of H. asinina in a complete randomized design with three replicates each. The experimental animals were reared in 15 glass aquaria for the first run and in plexiglass for the second run. Feeding of Navicula spp. was done once a day. Temperature and dissolved oxygen were monitored throughout the experiment. Data were analyzed using One-Way ANOVA to determine significant difference among treatments at 0.05 level of significance using Social Package for Social Science. Result of the first run showed that 32 ppt had the highest mean survival (1.50%) and mean settlement rate (1.84%). Similar result was also observed in 32 ppt with highest mean survival (9.72%) and mean settlement rate (16.42%). Significant difference existed among treatments during the second run of the experiment. Results showed that 28 ppt and 32 ppt were the optimum salinity levels for survival and settlement rate of H. asinina. Further study should be conducted to determine the tolerance and settlement rates of H. asinina larvae to lower salinities until it reaches juvenile stage with first respiratory pore appearing.
Conference paperJV Juario & WE Vanstone - In Proceedings of the International Milkfish Workshop Conference, May 19-22, 1976, Tigbauan, Iloilo, Philippines, 1976 - Aquaculture Department, Southeast Asian Fisheries Development CenterVertical salinity gradient columns were used to investigate the salinity preference of milkfish fry. Newly captured fry showed a preference for 32‰ salinity. Fry which had been in captivity for one to five days, at 12 or 22‰ salinity, had no salinity preference between waters of 12, 22 or 32‰ salinity.