life history broodstock –spawning and care –fertilization methods egg development and hatching...
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Life history• Broodstock
– Spawning and care– Fertilization methods
• Egg development and hatching– Stages of development– Methods of incubation
• Fry rearing• Fingerling stage• Growout stage• Harvest, transport and processing
Life history considerations
• Channel Catfish– Broodfish
• In nature may grow in excess of 20kg• Average size used in culture?
– 0.9 – 4.5 Kg» »
Channel Catfish
• Spawning– Late spring and summer– Manipulation of spawning time
••
– Sorting of sexes (Often difficult)During spawning
– Female – – Male –
»
Channel Catfish
• Use of Hormones– May use before putting in pond or pens– Human chorionic gonadotropin– Acetone-dried carp pituitary
• •
Channel Catfish
• Pond spawning (natural)– Must provide nest (Container)
• •
– Broodfish• 60-375 fish/hectare•
– Eggs (2 options)• Leave to hatch (male guards nest)•
– Nests • Inspect about 3X/wk
Channel Catfish
• Pen spawning– Used at some operations– Advantages
• • • removal of fish after spawning•
– Success is dependant on ability to select fish
Channel Catfish
• Aquarium/tank spawning– Provides greatest degree of control
• •
– Hormones required •
Channel Catfish
• Egg development and hatching– 5 to 10 days (optimum temp. – 26C)– Deposited as an adhesive mass– If removed to hatchery
• Hatch in trough (aeration – paddle wheel)
• Hatching jars -–
• survival rates (80-90%)
Channel Catfish
• Fry stocking (yolk sac absorbed at about 1 wk)– Treat ponds before stocking
• • • •
– If fry hatched in troughs• • Move to raceway or pond
– Grow to harvest•
Tilapia
• Almost all mouthbreeders– – –
• Advantages– multiple spawnings–
• Disadvantages– – female has reduced growth – reproduction
energy
Trout and Salmon
• Broodfish– Quality
• 3-5 yrs (commercial production)• 2 yrs – small eggs in most cases – low
fertilization rates: may strip eggs and return to growth cycle
– If wild caught or captured (dictates size)– – Separate male and females
• Males are more aggressive
Trout and Salmon
• Spawning methods– Handstripping
• Expel eggs by pressure to abdomen•
– Abdominal incision•
– Fish Killed– – Belly opened over container– Remaining eggs are shaken loose
Trout and Salmon
• Egg quality/ripeness– Check fish prior to spawning
• • Feel for “free” or loose eggs
– limit water, feces, dirt, or debris•
Trout and Salmon
• Fertilization methods– Dry method
• In container – ovarian fluid passes through: collected for virology
• – Wet method
• • Fertilization rates are usually lower
Trout and Salmon
• Fertilization methods– Delayed fertilization
• 4-6 females spawned• milt from multiple males
–
• “broken eggs”•
Trout and Salmon
• Egg stages– Water hardening
• increase uptake as egg contacts FW• • Disinfection can be done – decrease vertical
transmission risks• • Can be done in bucket, trays, or incubator•
Trout and Salmon
• Egg stages– Sensitive stage “Green eggs”
• •
– Eyed stage• Eyes visible to hatching• “shocking” occurs –
• • count (% eyed/fertilized)• • disease certifications
Trout and Salmon • Enumeration and sorting
– Weight method• 100 egg sample – get average weight• Drain water off eggs – lot wt.
–
– Displacement method• 50 eggs • • calculate # eggs/volume of water displaced
– Mechanical method• •
Trout and Salmon
• Egg disinfection– When received from other facilities
or at water hardening– – – Do not treat within 5 days of hatch