Supplemental Feeding of Tilapia in Fertilized Ponds
James S. Diana
School of Natural Resources and Environment
University of Michigan
Ann Arbor, Michigan, USA
C. Kwei Lin
Agricultural and Food Engineering Program
Asian Institute of Technology
Bangkok, Thailand
Kitjar Jaiyen
Department of Fisheries
Ministry of Agriculture and Cooperatives
Kasetsart University Campus
Bangken, Bangkok, Thailand
Abstract
(Printed as submitted)
The addition of feed to fertilized fish ponds was evaluated by adding feed
alone, feed plus fertilizer, or fertilizer alone to nine ponds stocked with
Nile tilapia Oreochromis niloticus. Two experiments were conducted. The
first had 500 fish per 250 m2 pond in 3-treatments: ad-libitum
feeding; fertilizer only; or fertilizer and ad-libitum feeding. The second
experiment had 5 treatments with 750 fish per pond: ad-libitum feed only;
fertilizer only; or 0.25, 0.50, and 0.75 satiation ration plus fertilizer.
Ponds in Thailand were maintained for 155-162 d, during which chemical and
physical properties were monitored. In experiment 1 tilapia growth was highest
in feed only ponds, and lowest in fertilizer only ponds. Net yield did not
differ significantly among treatments, due to variation in survival. In
experiment 2, tilapia growth was lowest in fertilizer only ponds, intermediate
in 0.25 ration ponds, and highest in 0.50, 0.75, and ad-libitum ponds. The
latter treatments were not significantly different. Multiple regressions for
each experiment indicated only 47-87% of the variance in growth was explained
by feed and fertilizer input, while 52-89% of the variance in yield was
explained by those factors. For both experiments combined, 90.3% of the
variance in growth was explained by feed input, fertilizer input, alkalinity,
and total inorganic nitrogen concentration. For yield, R2 was
0.888 and the regression included feed input, pH, and number of low dissolved
oxygen events. Experiment 1 appeared to approach carrying capacity near the
end, while no reduction in growth occurred in experiment 2 at higher fish
density and biomass. Reductions in growth in experiment 1 were not correlated
with declining water quality late in the grow out. Combinations of feed and
fertilizer were most efficient in growing tilapia to large size (500 g)
compared to complete feeding or fertilizing alone.
Appeared in Journal of the World Aquaculture Society 25(4).
PD/A CRSP
