Secondary data from the LLDA and the LGUs showed that 5,768 fisherfolks were affected by the knifefish infestation. The BFAR-National Inland Fisheries Technology Center conducted baseline survey to verify the extent of infestation in the lake.
The baseline survey conducted in key landing areas in Laguna de Bay covering 2,519 fishermen representing 43.67% of the affected fishermen showed that 4 municipalities in Rizal, 2 cities in NCR and 12 municipalities and 1 city in Laguna were affected by knifefish infestation. Result of the baseline survey on landed catch showed that knifefish comprised 40.34% of the catch in the open water at an average combined catch of 3,151.45 kg/day of the eight major fishing gears namely: gill net, long line, fish corral, fish shelter/manual seine, fyke net, fish trap, motorized drive in net and motorized push net.
The following morphological and biological characteristics were obtained in the Laboratory examination on the collected specimen:
1. The mouth of the knifefish is equipped with a razor sharp teeth, bony tongue and equally sharp gill rakers. It is an indication that the knifefish is highly carnivorous.
2. Analysis of the gut content showed remnants of heads/tails of small fishes equivalent to 32.29% of the food items present in the stomach ; scales and eyes of other fishes particularly Arius manilensis (kanduli) is 29.41% ; Shrimps is 17.65% and shell is 17.65%.
3. Relative fecundity is 20,000 pcs. of eggs in every kilogram of fish.
4. At 300 grams the fish starts to mature based on the observation of the ovary.
5. To grow to 1 kg, the fish consumes 7kgs of indigenous fishes and crustaceans in the lake.
Hence economic valuation indicates that a fisherman is losing Php 1,030.00 per kilo of knifefish produced.
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