Phytoplankton : Combination of Cost Reduction and Productivity Enhancement Technology Possible
“The natural food present in ponds produced through fertilization is enough to sustain needs of the fishes during the early stage of culture period
After its separate introduction of 45-days delayed feeding and polyculture technologies in various parts of Cagayan Valley, the fisheries bureau in the region has shown that both can be combined following successful result of its demo project here. The demo project was established in the fish farm of Marcia! Balmores in Barangay Catarawan this town.
Following recommended stocking rate on polyculture, the 1,520 square meter fishpond owned Balmores was stocked with 6,080 pieces size 22 tilapia (80%), and 380 common carp (5%) March 20 this year. The 1,14o pieces hito fingerlings were stocked two months later, or exactly halfway in the culture period to avoid possible predation.
Stocking rate is 5 pieces fingerlings per square meter.
Likewise, following protocol on 45-days delayed feeding technology, introduction of commercial or artificial feeds came one-and-a-half-month into the 4-month culture period as measure to save on feed cost.
“A key to delayed feeding is the propagation of plankton to serve as natural food for the fingerlings. This is done by applying chicken manure at rate of 1 to 2 tons per hectare and maintenance of water fertility using 16-20-0 inorganic fertilizer at rate of 100 kilograms per hectare thru tea bag method,” Hermogenes Tambalque, BFAR R02 Extension Chief said.
“The natural food (phytoplankton) present in the pond produced through fertilization is enough to sustain needs of the fishes during the early stage of culture period,” Tambalque said.
Polyculture meanwhile takes advantage of stratified feeding habit of the stocks being cultured such that direct feed competition is eliminated and maximum utilization of pond resources is ensured.
“A key to the success of this project is the symbiotic relationship of the cultured species. The carp, being pond bottom feeders and dwellers helped maintain water quality by eating excess feeds and other detritus. The hito meanwhile, prevented overcrowding and unnecessary feed and oxygen competition by feeding on fry or offspring of the tilapia,” Tambalque explained.
The aquaculture expert however emphasized proper stocking combination and composition on any polyculture project. “We can not stock 50% tilapia and 50% hito, knowing that hito are voracious feeders. This would result to undersized tilapia,” Tambalque explained.
As per result of final sampling shown during the Harvest Field Day last July 30, the hito reached an average body weight of 150 grams, carp at 180 grams, and the tilapia, being main culture species, at 240 grams. Survival rate were assumed at 85% to go% for the various species. Total production given this assumption is 1,453 kilos.
The carp were a little bit off target as the fingerlings stocked were small and of mixed size.
With retail price of 80 pesos per kilo for carp, 85 for tilapia, and 120 for hito, projected net income is 81,087.00 pesos from production expense of 47,460.00.
Total feeds consumed is 47 bags – significantly lower than current rule of thumb on tilapia culture which is 10 bags per thousand pieces.
Tambalque said that secondary species (carp and hito) are not taken into consideration when computingfor the daily feed ration in polyculture technology.
Balmores observed that fish grows well when there is natural food, presence of which can be determined through the greenish color of the water. Balmores also said that it is best to feed fish when the sun is up and before sundown as dissolved oxygen level is still high during those times.
“Avoid feeding at night as it might result to suffocation and mortality. Also pre-empt negative effect of afternoon downpour after a hot day by immediately freshening the pond to neutralize abrupt change in water temperature.
“Rarely can we reduce production cost and still have higher income and production, but this project has shown us precisely how. Polyculture and delayed feeding technology can ensure sustainability in the long term through reduced organic load in the pond system,” BFAR RO2 Regional Director Jovita Ayson said.
By Max Prudencio