Tambac fishkill, a case of greed
OVERSTOCKING, OVERFEEDING
IT seems some fishpond operators never learn. They continue to defy established parameters in a bid to double profits.
The fishkill in a two-hectare fishpond in Barangay Tambac in Dagupan last Thursday that killed 25,000 milkfish was due to overstocking and overfeeding, not from the natural phenomenon neap tide.
Field investigation conducted by technicians of the National Integrated Fisheries Technology Development Center (NIFTDC) indicate the fishpond was stocked with 35,000 milkfish, more than the suitable capacity.
Dr. Westly Rosario, NIFTDC chief, said at this time of the year, it is unwise to overstock when the water in rivers and ponds are hardly flowing, which results in the depletion of dissolved oxygen (DO) in the water.
The DO level at the Tambac fishpond, located at the back of the Dagupan City Water District, was 0.8, much lower than the critical DO level of two to three.
Rosario, speaking during the KBP Forum on Thursday, said the ideal stocking rate per hectare of fishpond at this time of the year is from 5,000 to 10,000 pieces.
Fishkill usually occurs early in the morning when the DO level goes down because of lack of sunlight.
To increase DO level, operators can put a motorboat at the edge of the fishpond and keep its rudder running for a few minutes to stimulate water circulation and give enough DO to the fish.
OVERFEEDING
At the same time, Rosario called on farmers to feed their fish sparingly nowadays as fish eat less during cold weather.
In the Philippines, he added, the cold weather is considered from September to December and could extend to January.
The excess feeds thrown to the fish drop to the bottom of the pond and rot.
This was another contributing factor to the fishkill in Tambac as technicians found that the 35,000 fish stock was being given at least 11 bags of feeds per day.
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