Preliminary notes on the salinity preference of milkfish, Chanos chanos, fry
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Vertical 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.
Juario, J. V., & Vanstone, W. E. (1976). Preliminary notes on the salinity preference of milkfish, Chanos chanos, fry. In Proceedings of the International Milkfish Workshop Conference, May 19-22, 1976, Tigbauan, Iloilo, Philippines (pp. 43-46). Tigbauan, Iloilo, Philippines: Aquaculture Department, Southeast Asian Fisheries Development Center.
PublisherAquaculture Department, Southeast Asian Fisheries Development Center
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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 paperF Hu & IC Liao - In Proceedings of the International Milkfish Workshop Conference, May 19-22, 1976, Tigbauan, Iloilo, Philippines, 1976 - Aquaculture Department, Southeast Asian Fisheries Development CenterGrowth of young milkfish was studied at different levels of salinity over a period 68 days. Results suggested that young milkfish reared in freshwater or less saline sea water grew faster than in sea water. The increase in body weight was neither due to the increase in water content nor increase in feeding rate. The difference in growth rate might be attributed to the deviation from the original acclimating salinity. Mechanisms of the effect of salinity in retarding or accelerating milkfish growth should be investigated in the future.
Growth and production of deformed and nondeformed hatchery-bred milkfish (Chanos chanos) in brackishwater ponds NS Sumagaysay, GV Hilomen-Garcia & LMB Garcia -
The Israeli Journal of Aquaculture-Bamidgeh, 1999 - Society of Israeli Aquaculture and Marine BiotechnologyThis study evaluated the growth and survival of morphologically deformed and nondeformed hatchery-bred milkfish in brackishwater ponds. It compared the size-frequency distribution of the nondeformed fish with the deformed ones, and determined the effects of different types of deformity on growth. The deformities include the absence of an upper jaw, a folded operculum with gills exposed, a cleft branchiostegal membrane, scoliosis, etc. The results were compared with production of wild stock. Hatchery-bred and wild milkfish fry were grown separately in nursery ponds (500 m2/pond) at 10 individuals/m2. After a month, the juveniles (average weight hatchery-bred 6.0 g; wild 9.5 g) were transferred to seven rearing ponds of 1000 m2 each (stocking density 3000/ha). Three ponds were stocked with selected, nondeformed hatchery-bred fish (unmixed stock), three ponds with a combination of deformed and nondeformed hatchery-bred fish (1:2 ratio; mixed stock), and one pond with wild fish. The final weight, specific growth rate and survival of the nondeformed fish (mixed and unmixed stock) after four months of culture were significantly higher (p<0.05) than those of the deformed fish. Production, however, did not significantly differ between the unmixed nondeformed (433 kg/ha) and the mixed deformed and nondeformed (377 kg/ha) fish. Survival of the deformed stock (56%) was significantly lower (p<0.05) than that of the nondeformed stock (86-88%). Approximately 92% of the deformed stock and 17-20% of the nondeformed were below 150 g. Severe deformities such as the absence of an upper jaw and exposure of all or most of the gills hindered fish growth, while widening of the operculum or branchiostegal membrane, scoliosis, or absence of the anal fin had less effect on growth. To lower the incidence of deformities in grow-out ponds, milkfish fry should be reared to the early juvenile stage in nursery ponds for at least a month. The harsh natural conditions in the nursery ponds (e.g., presence of predators, abrupt changes in salinity, temperature and dissolved oxygen) and stress during transfer to rearing ponds may eliminate most of the weak fish and those with severe deformities.