CULTURE OF GREY MULLETS. Grey mullets and milkfish are one of the important group of cultured...
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![Page 1: CULTURE OF GREY MULLETS. Grey mullets and milkfish are one of the important group of cultured species in Vallis of the Mediterranean lagoons (Italy) Coastal.](https://reader036.fdocuments.in/reader036/viewer/2022082411/5697c0041a28abf838cc4323/html5/thumbnails/1.jpg)
CULTURE OF GREY MULLETS
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• Grey mullets and milkfish are one of the important group of cultured species in
• Vallis of the Mediterranean lagoons (Italy)
• Coastal harbour culture' of China
• Gangetic and Southern estuaries of India
• Coastal fish ponds of Hawaii
• The striped mullet Mugil cephalus -widely distributed -larger size and faster growth rate
• Eurythermal and highly euryhaline; tolerating salinities between 0 and 75 ppt
• Feeds on detritus, large plants, blue green algae, green algae and diatoms
• Valued not only for meat but also for roe which is a delicacy in Taiwan and Japan
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Culture systems
• The traditional and extensive culture with other euryhaline species
• They are generally raised with other species in polyculture-
• In Hong Kong with Chinese carps
• In Taiwan with Chinese carps and Tilapias
• In Israel with common carp and tilapias
• In India with shrimps, pearlspot and other fish in traditional prawn culture systems
• In the Philippines and Indonesia with milkfish.
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Fry collection
• fry obtained from natural systems
• Striped mullet breeds in the sea, fry and fingerlings enter estuaries and congregate in shoals
• Fry collection -seines and dip nets are used
• Most suitable areas for collection are marginal areas of rivers, tidal streams, creeks, swamps and inundated fields. They swim against slow currents and such areas are ideal sites for collection
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Hatchery production• 1st in Taiwan -artificial propagation of stripped mullet
• 2.5 to 3 years old spawners are obtained from the sea and stocked in cement tanks
• They are injected with 3-5 mullet pituitary glands mixed with 20-50 rabbit units of synahorin (mixture of chorionic gonadotropin and mammalian hypophyseal extract) per female or with salmon gonadotropin
• Eggs with best chances of fertilization are released 40-50 hours after hormone injection
• A soft swollen belly with excretion of calcium deposits indicates they are ready to release eggs
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• Females are stripped and eggs are mixed with milt collected from males
• Both dry and wet fertilization can be followed. 1.0 to 1.5 million eggs can be obtained per female
• Eggs are incubated in flow through systems are in aquaria with static water and aeration
• Eggs hatch in 34 to 48 hours at a temperature of 24°C. Larvae are reared in indoor tanks
• Newly hatched larvae are planktonic, they swim with heads down and bellies up
• Larvae start feeding three days after hatching. They are fed fertilized oyster eggs. From 5th day onwards they are fed with rotifers and copepods
• In 45 days fry are ready for stocking in grow-out ponds.
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Grow-out operations
• Tidal stocking - quantity and composition of stock can seldom be determined
• The aquaculturists – wild caught
• Traditional culture system - Regular water exchange, Natural food enters along with the tidal water on which mullets and other fish feed
• They also feed on benthic algal mat growing in the ponds
• Production in this system varies from 150 – 1500 kg/ha
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• In Hong Kong – stocked @ 10,000 to 15,000 fingerlings of 7.5 cm long along with 1000 to 2000
Chinese carps per ha – Thinned out 3500 per ha when the fish grow to 12 cm size– Feed - rice bran for the first two months and thereafter a mixture of rice bran
and oil cake– Production varies between 2500 to 3500 kg/ha/year.
• In Taiwan – stocking - 3000 mullet fingerlings, 2000 milkfish, 3250 Chinese carps and 500
common carp– fertilized with super-phosphate @ 60 kg/ha– Feed - mixture of rice bran, soya bean cake and peanut meal– Striped mullet -300g in one year and 1.2Kg in the second year– 3 year old -2 Kg under pond conditions
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