Growth response of Nile tilapia fry to salinity stress in the presence of an ‘internal reference’ fish
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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.
CitationBasiao, Z. U., Eguia, R. V., & Doyle, R. W. (2005). Growth response of Nile tilapia fry to salinity stress in the presence of an ‘internal reference’ fish.
Biological stress; Biometrics; Brackishwater fish; Feed composition; Feeding behaviour; Fish culture; Fry; Growth rate; Inland fisheries; Salinity effects; Salinity tolerance; Stocking density; Tolerance; Genetics; Growth; Salinity; Strain; Oreochromis niloticus; Israel; Philippines, Luzon I., Nueva Ecija, Munoz; Thailand, Chacoengsao Prov., Bangkok; Internal reference
This work was made possible through financial support from the International Development Research Centre of Canada and the SEAFDEC. The authors thank A. Arago, B. Antazo and B. Banaag for their technical assistance.
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Enrichment of live food with essential fatty acids and vitamin C: effects on milkfish (Chanos chanos) larval performance The effects of essential fatty acids (EFA) and vitamin C-enriched live food on growth, survival, resistance to salinity stress and incidence of deformity in milkfish larvae reared in tanks were investigated. Larvae were either fed rotifers cultured on Chlorella sp. and newly hatched Artemia nauplii (control), highly unsaturated fatty acid (HUFA)-enriched rotifers and Artemia nauplii or HUFA+vitamin C-enriched rotifers and Artemia nauplii. Milkfish growth in outdoor nursery ponds was also assessed to compare with growth in indoor tanks. Milkfish fed rotifers/Artemia enriched with HUFA (32–48 mg dry weight, DW) or HUFA+vitamin C (33–45 mg DW) exhibited significantly (P<0.05) higher growth than those given unenriched live food (24–27 mg DW) after 40 days of culture. Growth of milkfish in nursery ponds (albeit lower in stocking density) showed similar trends as those reared in tanks. When subjected to salinity stress (Day 25), mortality of the HUFA+vitamin C-treated fish and HUFA-treated fish were significantly lower (P<0.05) than the control fish. Survival of 26-day old milkfish, however, did not differ significantly (P>0.05) among the treatment groups. Forty-day-old milkfish fed HUFA+vitamin C-enriched live food had significantly lower (P<0.05) incidence of opercular deformity (mainly cleft branchiostegal membrane) (8.4–14.7%) compared with those given HUFA-enriched (15.8–23.5%) or unenriched (27.3–33.5%) live food. Results demonstrated the effect of HUFA enrichment in enhancing milkfish larval growth and resistance to salinity stress but not overall survival. Moreover, HUFA and ascorbate supplementation decreased but did not totally eliminate incidence of opercular deformity in milkfish larvae.
Conference paperJME Almendras & P Punet - In CL Marte, GF Quinitio & AC Emata (Eds.), Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines, Tigbauan, Iloilo, Philippines, 4-5 May 1993, 1996 - SEAFDEC Aquaculture DepartmentThe first part of the study investigates the ability of ovine growth hormone (oGH) to enhance the hypo-osmoregulatory and growth performance of juvenile brown trout after exposure to sea water (SW). Three groups of fish were either intraperitoneally implanted with cholesterol pellet (sham) or with a cholesterol pellet containing 250 µg oGH (treated) or not implanted (control). While still in fresh water (FW), gill Na+/K+ATPase activity of the oGH-treated group was four times higher than that of sham and control groups. Exposure to SW resulted to dramatic increases in plasma electrolyte levels of the sham and control groups, whereas the oGH-treated group showed only minor perturbations in plasma electrolyte concentrations. Further increases in gill Na+/K+ ATPase activity were observed in the oGH-treated group after SW exposure, while in the sham and control, a lag time of seven days was needed before gill ATPase activity started to increase. Additionally, by the end of the experiment, oGH-treated fish were significantly larger than non-treated ones. The second part of the study examines the time course of changes in plasma GH levels and GH free binding sites and affinity of the organs involved in osmoregulation in juvenile brown trout kept in FW or exposed to SW. Plasma GH levels increased significantly one day after SW exposure, reaching a peak on the 14th day. Concomitantly, GH free binding sites in the gills and liver decreased significantly in trout exposed to SW but remained unchanged in trout kept in FW. Reduction in GH free binding sites in SW-exposed trout indicates occupation of the gill and liver GH receptor by GH during the course of SW adaptation which may point to a direct role of GH on gill and liver physiology during hypo-osmoregulation. The second part of the study examines the time course of changes in plasma GH levels and GH free binding sites and affinity of the organs involved in osmoregulation in juvenile brown trout kept in FW or exposed to SW. Plasma GH levels increased significantly one day after SW exposure, reaching a peak on the 14th day. Concomitantly, GH free binding sites in the gills and liver decreased significantly in trout exposed to SW but remained unchanged in trout kept in FW. Reduction in GH free binding sites in SW-exposed trout indicates occupation of the gill and liver GH receptor by GH during the course of SW adaptation which may point to a direct role of GH on gill and liver physiology during hypo-osmoregulation.
Salinity tolerance of larvae of the mangrove red snapper (Lutjanus argentimaculatus) during ontogeny Salinity tolerance and the effects of salinity on growth, condition factor and chloride cell (CC) densities were evaluated for Lutjanus argentimaculatus larvae during ontogeny. Tolerance of L. argentimaculatus larvae to abrupt changes of salinity from 32 ppt varied with age. Periods to 50% mortality (LT50) were significantly (P<0.05) longer for 0-day-old larvae than for 7-, 14- and 21-day-old larvae. Tolerance of abrupt salinity change increased remarkably, starting on day 28. Although abrupt transfer to test salinities caused substantial mortalities, L. argentimaculatus larvae, regardless of age (0-, 7-, 14-day-old), showed significantly longer LT50 when abruptly transferred to 8 and 16 ppt than for transfers to 24 and 40 ppt (P<0.05). Growth of L. argentimaculatus larvae at 16, 24, 32 (control) and 40 ppt was not significantly different either at the end of the first rearing phase (days 0–21) or second phase of rearing (days 22–50). Survival was significantly lowest at 40 ppt (4.3%) at the end of first phase of rearing (P<0.05). There were no significant differences in survival rates at the end of the second phase of rearing; however, the condition factor (K) of larvae reared at lower salinities was significantly higher than that of fish at 40 ppt (P<0.05). Gill epithelia of 42- and 50-day-old larvae showed increasing density of CC with increasing salinity.