DEVELOPING FEEDING TABLES FOR AQUACULTURE: USING CHANNEL CATFISH ICTALURUS PUNCTATUS AND RED DRUM SCIAENOPS OCELLATUS AS MODELS
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William A. Wurts
Kentucky State University Cooperative Extension Program
Research and Education Center
P. O. Box 469
Princeton, KY 42445-0469 USA
Cultured aquatic species are often fed on a percent of body weight basis or with feeding tables. When using the % body weight method, cultured species are weighed at routine intervals – biweekly and one month periods are common – and the daily feed rate is adjusted accordingly. Tables list changes in animal weight and feed fed over periods of time (days or weeks). These tables are frequently calculated using linear growth predictions. A common growth pattern for aquatic organisms is sigmoidal, an S-shaped curve. Early growth of juvenile aquatic animals is typically exponential (rapid); it then slows, becoming more linear. An opportunity to capitalize on a significant rapid growth phase is lost if the feeding of juvenile animals is calculated from infrequent weighings or tables based on linear growth. The end result is a longer period of time required to reach market or harvest size, which may necessitate a double growing season rather than a single season.
The use of tables based on exponential juvenile (and overall sigmoidal) growth patterns can improve feeding efficiency and water quality while significantly reducing the time required to produce a harvest size animal. The critical rapid growth phase for species like channel catfish and red drum occurs when fish are between 35-250 g each. These species can grow from 35 to 250 g in approximately 50-60 days and up to 560-680 g each after 175-180 days when fed in accordance with natural growth patterns. Using traditional feeding methods, weights of 340-450 g each are common after 175-180 days.
The data needed to generate a feeding table based on exponential/sigmoidal
growth are: an initial weight, a final weight, growth period in days and an
estimate of daily feed consumption as a % of body weight. Daily feed
consumption, as % body weight, can be estimated from the Food Conversion Ratio (FCR).
Using the equation ln(Wt)=ln(Wo) + kt and the data mentioned above, it is
relatively simple to create (with an inexpensive calculator) an accurate feeding
table that closely matches natural growth. The values Wo and
initial weight and weight at time t, respectively; t is time in days; k is a
rate constant; and ln is the natural logarithm. For example, red drum growth from 35 to 258 g in 61 days yields the equation ln(258) – ln(35) = 61 k (i.e. k = 0.033). Feeding tables developed for channel catfish which assumed the rate constant, k, to be 0.03 for fish from 45 to 240 g each (and growth to be linear from 240-685 g) produced fish with an average individual weight of 590 g within 175 days. The techniques presented here can be used to easily calculate reliable feeding tables for almost any cultured species (e.g. marine or freshwater shrimp).
For related information click on the topics below:
FEEDING TABLES FOR RED DRUM AND CHANNEL CATFISH.
(PowerPoint slide show) Presented as: Developing feeding tables for aquaculture: using channel catfish Ictalurus punctatus and red drum Sciaenops ocellatus as models. Aquaculture '98; Las Vegas, NV -- The international triennial conference and exposition of the World Aquaculture Society, the National Shellfisheries Association and the Fish Culture Section of the American Fisheries Society. Book of Abstracts, p. 589.
(pdf) GROWTH RATES OF JUVENILE RED DRUM (SCIAENOPS OCELLATUS) REARED ON COMMERCIAL SALMON FEED IN FRESH AND SALT WATER.
1993. Journal of the World Aquaculture Society, 24(3): 422-424.
FEEDING CHANNEL CATFISH.
(view also as PDF) As: Review of feeding practices for channel catfish production. World Aquaculture, 32(4): 16-17 & 68.
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