Questions and Answers
What is the maximum length of a male milkfish?
At what age does a milkfish reach sexual maturity?
What type of diet do adult milkfish consume?
During what months does spawning typically occur for milkfish?
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What is the maximum weight a milkfish can reach?
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Which of the following habitats is not commonly associated with milkfish?
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How many eggs can a female milkfish produce per kilogram of body weight?
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Which marine environment do milkfish frequently enter?
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What is the term used to describe the reproductive strategy of milkfish?
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Which of the following food sources is not typically part of the milkfish diet?
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What is the maximum recorded age of a milkfish?
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Which of the following statements about milkfish habitat is true?
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What is the typical spawning behavior of milkfish regarding lunar cycles?
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What is the typical maximum length of female milkfish?
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Which of the following best describes the reproductive strategy of milkfish?
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Which type of environment do milkfish NOT typically inhabit?
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What type of trophic roles do milkfish fulfill in their feeding habits?
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What factors influence the spawning of milkfish?
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How many eggs can a milkfish female produce in relation to her body weight?
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In which of the following instances would you typically observe milkfish in freshwater environments?
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What is the initial water change percentage when the shrimp larvae reach PL 1 stage?
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How often is bacterial analysis performed on larvae starting from the PL 1 stage?
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Which step is NOT part of the process before harvesting postlarvae?
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At what stages are PCR analyses and fry quality monitoring conducted?
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What is the primary purpose of reducing the water level to 1/4 of the total volume before harvesting?
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What is the primary purpose of having a separate spawner/broodstock facility in a shrimp hatchery?
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Which action is NOT part of the recommended biosecurity measures before introducing spawners or broodstocks?
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What is the most effective way to prevent cross-contamination between spawning tanks?
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Which item is explicitly mentioned as a biosecurity measure at the entrance of the hatchery?
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Why is the use of UV-sterilized seawater recommended in the indoor culture of diatoms?
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Study Notes
Basic Biology of Milkfish
- Scientific name: Chanos chanos
- Habitat: Inhabits benthopelagic zones in freshwater, brackish, and marine environments, typically in depths of 1-30 m.
- Geographic distribution: Found in offshore marine waters, shallow coastal embayments, estuaries, and occasionally in freshwater streams.
Physical Metrics
- Maximum length: 180 cm for males, 124 cm for females.
- Maximum weight: 14 kg.
- Lifespan: Can live up to 15 years.
Feeding Habits
- Diet: Primarily herbivorous and omnivorous.
- Juveniles and adults feed on cyanobacteria, soft algae, small benthic invertebrates, and pelagic fish eggs and larvae.
Reproductive Biology
- Reproductive system: Gonochoric, meaning individuals are either male or female.
- Sexual maturity: Reached at around 5 years of age when they attain a size of approximately 70 cm.
- Spawning period: Occurs between March and November.
- Spawning behavior: Eggs are released 3-4 days before and after the full moon, with an average of 200,000 eggs per kg of female body weight.
Broodstock Development and Management
- Essential for sustainable hatchery operations, emphasizing the importance of understanding life history stages and reproductive cycles.
Basic Biology of Milkfish
- Scientific name: Chanos chanos
- Habitat: Inhabits benthopelagic zones in freshwater, brackish, and marine environments, typically in depths of 1-30 m.
- Geographic distribution: Found in offshore marine waters, shallow coastal embayments, estuaries, and occasionally in freshwater streams.
Physical Metrics
- Maximum length: 180 cm for males, 124 cm for females.
- Maximum weight: 14 kg.
- Lifespan: Can live up to 15 years.
Feeding Habits
- Diet: Primarily herbivorous and omnivorous.
- Juveniles and adults feed on cyanobacteria, soft algae, small benthic invertebrates, and pelagic fish eggs and larvae.
Reproductive Biology
- Reproductive system: Gonochoric, meaning individuals are either male or female.
- Sexual maturity: Reached at around 5 years of age when they attain a size of approximately 70 cm.
- Spawning period: Occurs between March and November.
- Spawning behavior: Eggs are released 3-4 days before and after the full moon, with an average of 200,000 eggs per kg of female body weight.
Broodstock Development and Management
- Essential for sustainable hatchery operations, emphasizing the importance of understanding life history stages and reproductive cycles.
Hatching and Harvesting Process
- Gradual water release from hatching tank to harvesting box with UV-sterilized seawater.
- Use a dipper to scoop nauplii and place in aerated pail.
- Count nauplii before transportation to ensure accurate stocking number.
- Nauplii transported in clean, covered pails from Spawner/Broodstock Facility to hatchery.
- Acclimatize nauplii for 30 minutes before transferring to tanks.
Water Management
- Water changes occur post-metamorphosis to PL stage, every other day, based on water quality.
- Initial water change begins at 10% for PL 1, increasing to 50% as they mature.
Monitoring Water and Fry Quality
- Daily larvae monitoring for disease detection.
- Bacterial analyses conducted bi-weekly starting at PL 1.
- PCR and fry quality monitoring occur at PL 5, 10, and 15.
- Sampling of shrimp larvae to estimate counts at various growth stages.
Harvesting of Postlarvae
- Prepare harvesting net inside the harvesting pit; add UV-treated seawater.
- Reduce water level in tanks to 1/4 to minimize drain pipe pressure and postlarvae stress.
- Controlled flow of tank contents into harvesting net for postlarvae collection.
- Concentrate harvested postlarvae using a clean scoop net into a basin with UV-sterilized seawater.
Packing and Transport of Shrimp Fry
- Place harvested fry in UV-sterilized seawater basins equipped with aeration.
- Strict biosecurity measures prevent disease exposure and contamination.
- Biosecurity steps include: separate spawner facility, cleaning and disinfecting tanks with 200 ppm chlorine, and soaking materials in disinfectant.
Spawner and Broodstock Management
- Acclimatization of Penaeus monodon spawners begins upon arrival using aerated, clean basins.
- Salinity levels are equalized between transport water and facility water.
- Disinfection performed with 50 ppm povidone-iodine.
- Spawners are sorted based on gonadal maturity before being placed in spawning tanks.
Eyestalk Ablation
- Eyestalk ablation is necessary for female Penaeus monodon maturation.
- Only perform ablation on hard-shelled females; mortality rate should be under 10%.
- Spawning can occur within three days following successful ablation.
Egg Disinfection and Treatment
- Clean spawning tank post-egg removal by siphoning and using a scoop net for dirt.
- Disinfect eggs with a solution of povidone-iodine mixed in seawater.
- Wash eggs through a sequence of three basins for disinfecting and rinsing.
- Eggs subsequently placed in a clean tank with UV-sterilized seawater for hatching.
Nauplii Monitoring and Stocking
- Check hatching tanks the morning after spawning to monitor nauplii emergence.
- Stock nauplii only from PCR-negative spawners to minimize pathogen transfer.
- Vertical transmission of pathogens occurs from mother to offspring; only healthy nauplii are used for stocking.
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Description
Explore the basic biology of the milkfish, including its habitat, physical metrics, feeding habits, and reproductive biology. This quiz covers essential details on the fish's lifecycle and ecological preferences. Test your knowledge about this unique species and its role in marine environments.
