- The economics of stocking size of fingerling and
stocker catfish in foodfish production ponds
Steeve Pomerleau and Carole Engle
A two-year catfish farm model was developed using mathematical
programming techniques. The LP model focused strictly on the
modular catfish production system. The objective function was
to maximize expected net returns over a two-year period by
selecting the optimal stocker production strategy subject to
pond balance, fish balance, and other production constraints.
The model allocated approximately 30% of the farm water-area
to stocker production and the remaining 70% to growout. The
model selected stocker production from 10-cm fingerlings
stocked at 100,000/ha because this strategy resulted in the
lowest cost/kg of stocker produced because it generated the
highest yields (kg/ha). In the model, fingerlings were grown
for a year and the resulting stockers were transferred to
growout ponds at a size of 255 g. Sensitivity analysis
indicated that the model was robust to large variations in
financial variables. The profit maximizing strategy selected
by the model did not significantly change with variations in
harvest costs from 0-200% of baseline, foodfish prices from
$1.10 to $1.76/kg, fingerling prices from 50 to 150% of
baseline, feed price from $225 to $300/metric ton, feed
conversion ratios from 1.5 to 3.0, or mortality rates from 0
to 0.33%/day.
- The effect of multiple-batch channel catfish ictalurus
punctatus stocking density and feeding rate on water quality,
production characteristics and costs
Brent E. Southworth*, Carole R. Engle, Nathan Stone and
Andrew A. Goodwin
With increases in production intensity, farmers must seriously
evaluate the effects of interactions among stocking density,
feeding rate and water quality on production. Fingerlings 4-6
inches were understocked at four densities ranging from
3,500-14,000 fish/acre with 2,000 lb/ac of 0.81-0.99 lb fish
into 12 0.25-acre ponds. Fish were fed daily to apparent
satiation with (32% floating feed). Water quality measurements
included nitrite, nitrate, total ammonia-nitrogen, Secchi
disk, chlorophyll a, total nitrogen, total phosphorus,
chemical oxygen demand, total alkalinity, total hardness,
chlorides, pH, temperature and dissolved oxygen. Costs of
producing channel catfish at different stocking densities were
estimated. Feed conversion ratios ranged from 2.33 to 1.61.
Maximum daily feeding rates were 128, 108, 164 and 160 lb/ac/d
in the 3,500; 7,000; 10,500 and 14,000 fish/acre densities
respectively. Gross yields were 6,763; 5,263; 7,363 and 7,183
lb/ac in the 3,500; 7,000; 10,500 and 14,000 fish/acre
densities respectively. Water quality did not deteriorate with
increases in stocking density and showed few significant
differences at sampling periods and no differences when
averaged across the production season (P < 0.05). Total
ammonia-nitrogen levels reached a maximum of 5.1 ppm in the
10,500 fish/ac stocking density. However, un-ionized ammonia
did not reach toxic levels in any treatment.
- Reducing catfish farm losses due to dockages assessed
by processing plants
Nathaniel Wiese, Carole Engle, and Jeremy Trimpey
Dockages can have a significant effect on catfish farm
revenues. This study was conducted to quantify common
dockages, examine seasonal and yearly variations in dockages
assessed, and determine optimal production practices given
various dockage scenarios. A convenience survey of invoice
records from 30 commercial catfish farms and 10 processing
plants provided 3,686 daily catfish load records that were
used to quantify dockages. A linear programming model was
developed to examine optimal production practices given 11
alternative production scenarios with five size grading
technologies subject to 24 types and levels of dockages. The
survey revealed that 95% of catfish loads delivered to
processing plants between 1997-2002 were assessed dockages
that resulted in an average farm revenue loss of 2.45% over
the study period. The most profitable production practice,
with respect to plant discount policies is to grow catfish in
a single-batch system for the entire growing season. Net
grading was used if the value of small fish returning to the
pond was not accounted for. However, off-flavor, cash flow
constraints, disease, marketing, and other factors force
farmers to use multiple batch systems. The UAPB grader was
selected primarily when the value of fish returned to the pond
was accounted for. This study suggested that there are
combinations of management strategies and grading technologies
that can be used to minimize losses due to dockage. Larger
farm sizes and increasing minimum market sizes of fish are
conditions under which a move to either single-batch
production or intensive grading would result in higher farm
revenues. Smaller farms, with multiple-batch production
systems would have higher farm revenues with net grading at
5-10% tolerances, but with the UAPB grader at 0% tolerances.
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