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General Information

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This species has now become the most important cultured species in in the USA: ... Clean harvest system: goal is to have only one year class of fish in the pond. ... – PowerPoint PPT presentation

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Title: General Information


1
Channel Catfish (Chapter 17)
  • General Information
  • Until relatively recently, channel catfish were
    not viewed favorable by the average consumer
  • This species has now become the most important
    cultured species in in the USA
  • In 2000, 50 of the commercial fish culture
    harvest was channel catfish
  • 95 of this production occurs in 4 states
    Mississippi (70), Alabama, Arkansas, Louisiana
  • Channel catfish is second only to largemouth bass
    as sports fish
  • Topics
  • Biology
  • Commercial culture
  • Culture facilities
  • Production practices
  • Water quality management
  • Harvesting and processing
  • The future of channel catfish farming

2
Channel Catfish
  • Biology
  • Order Siluriformes, family Ictaluridae (39
    species Canada to Central America)
  • Channel catfish is native to central North
    America
  • Slender and scale-less normally pigmented fish
    are white to silvery on the undersides shading to
    grayish blue or black on the back. Albinism is
    uncommon in the wild but is seen in domesticated
    strains
  • Eight barbels, 4 dorsal and 4 ventral
  • Soft-rayed fins, but spines on dorsal and
    pectoral fins
  • Rounded anal fin contains 24-30 rays used to
    distinguish channel catfish from other species
    deeply forked tail fin in younger individuals but
    not so much as they grow older (see figure)
  • Native habitat includes clear and flowing
    streams, sluggish rivers, lakes, and ponds
    bottom dweller, prefer sand and gravel
  • Omnivorous
  • Hardy fish (temp just above freezing to 34-35 C
    salinity 0-11 ppt)
  • Sexual maturity achieved at 2-12 years may live
    up to 20 years and reach up to 20 kg in nature,
    2-4 years to achieve 0.5 Kg
  • Spawning usually occurs in late spring.
    Temperature very important.
  • Males select spawning site and attract females to
    breed, and chase them away after spawning males
    care for the egg masses until hatching (5-8 days)

3
Channel Catfish
  • Commercial Culture
  • Origins
  • Channel catfish have always been a popular food
    fish in southeastern USA
  • Regional popularity of this species stimulated
    interest in pond culture in the 1950s and 1960s
  • Local markets remained the outlet for all
    production
  • Expansion
  • Rapid rate of expansion started about 1975
  • In part due to declining profits from traditional
    agriculture (cotton, soybeans) and desire to
    diversify agriculture
  • Establishment of large feed mills and fish
    processing plants also assisted in the expansion
    effort
  • 1980 15,000 ha of ponds and 35,000 mt production
  • 2000 80,000 ha of ponds and 270,000 mt
    production
  • Favorable attributes of channel catfish
  • Hardy fish broodstock relatively easy to spawn
  • Grow-out stock do not spawn in culture ponds
  • Do not require special feeds (commercial feeds
    available for all growth stages)

4
Channel Catfish
  • Culture Facilities
  • Over 98 of channel catfish in the USA are grown
    in earthen ponds because of lower production
    costs
  • Two types of ponds are used
  • Watershed ponds built in hilly areas by damming
    small streams disadvantage is that large groups
    of ponds cannot be set up (because of water
    quality problems) and large scale operations of
    scattered ponds makes management more difficult.
    This type of ponds used to some degree in
    Alabama.
  • Embankment ponds built on flat land by digging
    a pond (1-2 m depth) and using the removed soil
    to form levees or embankments. Most common type
    of catfish pond (90). Pond size is compromise
    between ease of management and operation costs
    typically 4-8 ha per pond, rectangular in shape.
    Typically, source of pumped water is needed. See
    Fig. 17.2.

5
Channel Catfish
  • Production Practices
  • Spawning and breeding
  • Production sequence begins with spawning of
    broodstock
  • Spawning begins in spring when water temperatures
    reach gt 20 C (25-27 C seems optimal)
  • Sexual maturity can be observed at 2-y-old fish
    weighing 0.3 kg. However, 3-y-old fish weighing
    1.5 Kg are needed for reliable spawning. Prime
    spawners 4-6-y-old fish at 2-4 Kg produce
    6500-9000 eggs (relative fecundity decreases with
    age beyond this age bracket)
  • Broodstock that are held in ponds will spawn in
    spawning containers, such as buckets egg
    masses are then moved to the hatchery. Placement
    of the spawning containers can be used to control
    the timing of spawning. They are checked every 2
    or 3 days for the presence of eggs. See Figs.
    17.3-17.4
  • Normally, there is no need for artificial
    induction of spawning (by hormone injections) and
    artificial fertilization, unless planned crosses
    are desired
  • Brood fish are maintained at low standing crops
    (lt 2500 Kg fish/ha)
  • Optimal sex ratios in brood ponds 2 males for 3
    females (see figure)
  • Females only spawn once a year, but males can
    spawn 2-3 times
  • At temperatures gt20 C, brood fish are fed daily
    1-2 of their body weight (prepared diet) at
    13-20 C, less feed every other day at lt13 C,
    they dont feed much

6
Channel Catfish
  • Production Practices
  • Spawning and breeding (continued)
  • Before 1986, no planned breeding was conducted
    other than selection of broodstock for general
    performance traits
  • In 1986, the USDA began research to improve the
    genetic potential of channel catfish. The first
    general release occurred in 2001 NWAC-103 line.
    This line has excellent growth compared with
    other strains available to the industry

7
Channel Catfish
  • Production Practices
  • Hatchery practices
  • Channel catfish hatcheries are simple facilities
    that use single-pass, flow-through tanks for egg
    incubation and fry rearing
  • Good water quality is required temperature may
    be most important single factor (Table 17.1)
  • Shallow rectangular tanks are used for eggs and
    fry
  • Eggs are placed in baskets along the length of
    the tank, which is equipped with a series of
    paddles attached to a shaft running the length of
    the tank to simulate the fanning of males
    guarding the nests. Incubation varies according
    to water temperature (5-8 days at 25-28 C). See
    figure
  • At hatching, sac-fry fall through the mesh of the
    basket and congregate in the corners of the tank
  • MacDonald jars are also used in some hatcheries
    after separation of eggs from the egg mass by
    treatment with sodium sulfite (see figure)
  • Fry are transferred to similar tanks, but without
    the paddles. They are fed after they begin
    swimming (6-12 times daily)
  • They are transferred to nursery ponds after 2-10
    days of feeding in the hatchery tanks

8
Channel Catfish
  • Production Practices
  • Nursery pond management
  • Fry stocking density determines the average size
    of fingerlings after one season of growth
    (150-180 days). To produce 20 g fingerlings,
    stocking rate should be 200000-300000 fry/ha
  • Nursery ponds should be fertilized (inorganic N
    and P) 3-4 weeks prior to stocking zooplankton
    will support fry for several weeks after stocking
  • Fingerlings are then fed prepared diet 1-2 times
    daily to satiation about one month after stocking
  • After 5-9 months fingerlings are harvested and
    transferred to grow-out ponds
  • Size grading is usually necessary (by seine) to
    obtain a uniform population size for stocking
  • Nursery ponds are drained and dried after harvest
    is completed

9
Channel Catfish
  • Production Practices
  • Grow out
  • Management of grow out varies considerable from
    farm to farm
  • Clean harvest system goal is to have only one
    year class of fish in the pond. Fingerlings are
    stocked, grown to a desired size (0.4-0.5 Kg) and
    completely harvested either all at once or over
    2-4 seinings over several months. This system
    still used by some farmers using watershed ponds
  • Understocking system provides year-round supply
    of food size fish. Initially, a single cohort of
    fingerlings are stocked. The faster-growing fish
    are harvested using a large-mesh seine and new
    fingerlings are added to replace those taken out.
    This process continues for years without
    draining the pond. This is by far the most
    widely used system
  • Advantages of clean-harvest system fish tend to
    be more uniform in size easier to maintain
    inventory (zeroed out after complete harvest)
    food conversion efficiencies tend to be better
    also, at least in theory, better disease
    management
  • Advantages of understocking system fish of
    marketable size available for most of the year
    can manage to avoid off-flavor (more ponds to
    chose from) this is most important reason for
    this system being more commonly used than
    clean-harvest system.

10
Channel Catfish
  • Water Quality Management
  • Because of high stocking densities and feeding
    rates at catfish farms, large amounts of
    metabolic waste are generated. Since water is not
    replaced during the culture period, this waste
    can lead to environmental deterioration. Three
    factors are of primary concern
  • Dissolved oxygen
  • Ammonia and nitrite
  • Off-flavors

11
Channel Catfish
  • Water Quality Management
  • Dissolved oxygen
  • Phytoplankton metabolism is most important factor
    affecting DO in catfish ponds. Dense
    phytoplankton blooms can cause DO to fall to
    critical levels (3-4 mg/L) at night.
  • Aeration is thus needed, usually starting at
    night and continuing during the daytime until
    levels have recovered.
  • Metabolism is affected by temperature. Thus,
    fluctuations in DO levels are not as wide when
    temperatures cool down during the cool/cold
    season. At temperature lt15 C, problems of DO are
    uncommon.
  • Paddlewheel aerators are most common device used

12
Channel Catfish
  • Water Quality Management
  • Ammonia and nitrite
  • Ammonia excretion by fish is proportional to
    amount of feed consumed about 0.03 Kg of ammonia
    per Kg of feed consumed
  • Ammonia accumulation is usually not a problem in
    catfish ponds
  • However, nitrite has been known to occasionally
    accumulate in catfish ponds, especially in spring
    and fall when environmental conditions are
    rapidly changing.
  • Nitrite combines with hemoglobin in blood to form
    methemoglobin and impairs oxygen transport and
    respiration (nitrite toxicosis)
  • Nitrite toxicosis can be prevented by making sure
    that adequate levels of chloride (salinity) are
    present in water. Chloride competes with nitrite
    for intake by the gill. A ratio of 10mg/L of
    chloride for every 1 mg/L of nitrite-nitrogen is
    sufficient.

13
Channel Catfish
  • Water Quality Management
  • Off-flavors
  • Off-favors can be caused by
  • Feed ingredients
  • Post-mortem rancidity
  • Odorous compounds absorbed from the environment -
    this is the most common reason
  • Geosmin and 2-methylisoborneol, odorous
    metabolites produced by certain blue-green algae
    (cyanobacteria), are most commonly responsible
    for off-favors in farm-raised channel catfish
  • It is standard practice to taste-test fish
    before scheduling pond harvests
  • Reasons for the occurrence of odor-producing
    cyanobacteria are not fully understood, and thus
    at the present time it is not possible to
    reliable manage catfish ponds to prevent
    off-flavors.
  • Fish with off-flavors are simply left in the pond
    until the cyanobacteria disappear and the
    off-flavor goes away. Alternatively, fish may be
    moved to clean pond, but this process is labor
    intensive and stresses the fish.

14
Channel Catfish
  • Harvesting and Processing
  • Harvesting is usually accomplished using
    tractor-pulled seines with mesh sizes selected to
    capture the desired fish size normally, a square
    mesh size of about 4 cm is used to capture fish
    greater than about 0.4 Kg.
  • See Figs. 17.5-17.7
  • A variety of products are marketed fillets,
    nuggets, steaks, and whole dressed fish. About
    53 of the fish carcass can be processed into
    saleable product. Frozen fillets account for the
    largest portion of total sales (about 40).

15
Channel Catfish
  • Future of Channel Catfish farming
  • Channel catfish culture expanded at a remarkable
    rate from 1980 to 2000
  • Future growth may be constrained by large capital
    investment needed to enter the industry and
    increasingly strict government regulations
    concerning environmental issues.
  • Annual yields average about 4000 Kg/ha, which is
    half of what can be achieved under controlled,
    experimental conditions. Thus, technological
    improvements at the farm may be able to lead to
    higher yields.
  • Better understanding and management of
    off-flavors, improved strains of fish and
    improvements in feeding practices may also help
    the industry
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