Gender Determination, Care, Water Quality Management, and Nutrition.
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Transcript of Gender Determination, Care, Water Quality Management, and Nutrition.
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Broodfish ManagementGender Determination, Care, Water Quality
Management, and Nutrition
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Gender DeterminationSex of broodfish
should be determined so that females and males can be stocked into brood ponds at the desired ratios
The urogenital area is located ventrally, posterior to the anus and anterior to the anal fin
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Gender DeterminationThe male releases sperm through an opening
called the urogenital poreThe female has two separate openings – an
anterior genital pore for expulsion of eggs and a posterior urinary pore for release of urinary products
The two openings on the female are located in a groove with surrounding tissue forming a distinguishable slit just below the anus
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Gender Determination
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Gender DeterminationMature fish have secondary sexual
characteristics that are also useful for selection
These characteristics are most evident near spawning time
The male hasA broad, muscular head wider than the bodyThickened lipsOften a grayish mottling on the underside of
the jaw and abdomen
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Gender DeterminationThe female has
A narrower than the bodyShe usually lacks the muscularization and
pigmentation common in malesA well-rounded abdomen that extends past the
pelvic fin region into the genital area during the spawning season A hard to the touch abdomen is probably filled with
feed A soft, palpable abdomen indicates that the ovaries
are well developed
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Gender Determination
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Gender DeterminationBroodfish usually eat much less during the
spawning seasonIt is not difficult to tell if a female has well
developed ovaries or a belly full of food
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CareA common management practice among
fingerling producers is to have separate ponds for holding and spawning
Stocking densities in holding ponds are usually 2,000 to 3,000 lbs/acre
Spawning ponds need to be new pondsThey should be newly renovated ponds or
former fingerling ponds that have been thoroughly dried out and exposed to air for several months after the sale of fingerlings in the winter and spring
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CareStocking densities in spawning ponds is
usually 800 to 1,200 lbs/acreMale-to-female sex ratio should be
approximately 2:3Broodfish are kept in the spawning pond until
spawning ceases and then removed with a large-mesh seine and returned to holding ponds
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Water Quality ManagementWater quality must be
maintained in broodfish ponds to ensure the survival of the broodfish and the production of large numbers of good quality eggs
Excess nutrients from feed is the main reason for a decline in water quality
Poor water quality stresses the fish, making them more vulnerable to diseases and parasites Poor water quality contains low
dissolved oxygen levels and high levels of ammonia, nitrites, and carbon dioxide
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Water Quality ManagementAdding feed to the water also adds nitrogen
and phosphate, nutrients that can increase phytoplankton production
The phytoplankton use oxygen at night, creating an even greater oxygen demand than a pond with fish alone
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Water Quality ManagementPoor water quality should be
corrected before the fish become diseased and die
Options include: Temporarily reducing feeding
to limit the nutrients in the water
Aerating to increase the amount of oxygen in the water The most popular aerators are
large, paddlewheel aerators Fountain aerators are also used
Flushing the pond with water from a well or reservoir Often void of oxygen and
requires emergency aeration
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Water Quality ManagementProducers should have emergency aeration
equipment availableGenerally, the first sign of poor water quality
is that the fish stop feeding or reduce the amount of feed they consume
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NutritionIn broodfish, the reproductive
performance is more important than the growth rate
Adequate food should be supplied especially during egg formation and development
Underfed catfish have low reproductive success and poor egg quality
A pond with both sexes with insufficient food supply can result in poor quality female broodfish because the larger, more aggressive males will consume most of the limited ration
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NutritionBroodfish are usually fed the same feed used for food
fish grow outA sinking feed can be used for broodfish that are
more hesitant to feed at the surfaceA nutritionally complete feed of at least 32 percent
crude protein is fed at about 2 percent of body weight daily in water temperatures above 70F
A ration consisting of about 1 percent of the body weight is fed on alternate days in water temperatures of 55 to 70F
About 0.5 percent of the body weight is fed once a week in water temperatures below 55F
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NutritionForage fish can be stocked into broodfish
ponds to ensure that ample food is consistently available during the egg production period
The most common forage fish is the fathead minnow
They are stocked in the late winter or early spring at 5 to 10 pounds per acreSome structure can be added to the ponds to
enhance minnow reproduction