Cur­rents

CALAUAN is a sec­ond-class mu­nic­i­pal­ity in the prov­ince of La­guna about 75 kilo­me­ters south of Manila. It has a pop­u­la­tion of more than 80,000 peo­ple and el­e­va­tion of 65 me­ters above sea level. While it is known as “The Home of the Sweet­est Pineap­ple in La

Agriculture - - Contents - >BY DR. RAFAEL D. GUER­RERO III

We vis­ited the tilapia hatch­eries in Barangay San Isidro in Calauan re­cently to as­sess their set­ups. The hatch­eries con­sist of earthen ponds that were de­vel­oped from once ir­ri­gated rice fields. Wa­ter is mainly from an ir­ri­ga­tion source. Rang­ing in size from 1 to 6 hectares per hatch­ery, the hatch­ery ar­eas are leased by fi­nanciers from their own­ers who may also be em­ployed in the op­er­a­tions.

The tilapia breed­ing and nurs­ery ponds in the Calauan hatch­eries mea­sure 300-600 m2 each or larger with wa­ter depths of 0.6-1 me­ter. Nile tilapia breed­ers (ma­ture male and fe­male fish) with body weights of 50-80 grams a piece (3-4 months old) are ini­tially stocked in the ponds at a den­sity of 4-5/m2 and sex ra­tio of 5 fe­males to a male. With feed­ing of com­mer­cial pel­lets, 500 of the breed­ers can pro­duce 100,000 fry in a month dur­ing the good weather months of June to Novem­ber. Fry re­leased by the mouth-brood­ing fe­male breed­ers are col­lected 2-4 times a day along the edges of the breed­ing ponds at about 10 days from stock­ing of the breed­ers for 2-3 weeks us­ing fine-mesh dip nets.

After a month of breed­ing, the ponds are drained and the breed­ers are trans­ferred to net cages in nearby ponds for con­di­tion­ing (rest and re­cu­per­a­tion) pe­riod of 3-7 days. The breed­ers are then re­stocked in the ponds for the next breed­ing cy­cle. The breed­ers are uti­lized by the hatch­eries un­til they at­tain weights of more than 300 grams each in about 18 months when their pro­duc­tive­ness de­clines.

Most of the 1-2-day old fry (from the time they are re­leased by the fe­males) pro­duced in the Calauan hatch­eries are bought by buy­ers who sup­ply the nurs­ery op­er­a­tors in Lau­rel, Batan­gas. Rear­ing of the fry to fin­ger­ling-sizes (more than 1 inch long) is done in nurs­ery ponds for 5-6 weeks be­fore be­ing brought to the lake for fur­ther growth in float­ing nurs­ery cages and stock­ing in the grow-out cages. The fry are sold at R4,000 per thou­sand ( R0.04 each) in Calauan and trans­ported in closed plas­tic bags with wa­ter and pres­sur­ized oxy­gen.

Some hatch­eries in Calauan like the MGB Aqua­farm treat the newly-col­lected fry for sex re­ver­sal by feed­ing a com­mer­cial male hor­mone-feed for three weeks in nurs­ery ponds at a stock­ing den­sity of 500/m2.The treat­ment en­hances the growth of the fry and re­sults in their be­ing 95-99% males which

makes them yield more in the grow-out cages be­cause of the male’s growth ad­van­tage over that of the fe­male in the species. After the sex re­ver­sal treat­ment pe­riod, the fin­ger­lings are fur­ther reared to larger sizes in the ponds for an­other 2-3 weeks be­fore be­ing brought to Taal Lake for stock­ing in float­ing nurs­ery and grow-out cages. Trans­port of the fin­ger­lings from La­guna to Batan­gas is also done us­ing oxy­genated plas­tic bags with wa­ter. The sex-re­versed fin­ger­lings sell for R0.45-R0.50 each.

The ma­jor prob­lems en­coun­tered by the tilapia hatch­ery op­er­a­tors in Calauan are mainly re­lated to weather con­di­tions. Dur­ing the hot months (April-May), wa­ter tem­per­a­ture in the ponds (higher than 32OC) can cause mor­tal­i­ties par­tic­u­larly for the fry/fin­ger­ling due to heat stress. On the other hand, dur­ing the cool sea­son (De­cem­ber-Fe­bru­ary) when wa­ter tem­per­a­tures can be 24-26OC, fry pro­duc­tion goes down by as much as 50% be­cause of the re­duced breed­ing ca­pac­ity. Breed­ers tend to be in­ac­tive and take in less feed at lower wa­ter tem­per­a­tures com­pared to their nor­mal tem­per­a­tures of 28-32OC.

The hatch­ery op­er­a­tors of Calauan also said that they need gov­ern­ment as­sis­tance in the form of tech­ni­cal ser­vices (ex­ten­sion), improve­ment in the qual­ity of tilapia breed­ers and fi­nanc­ing with low in­ter­est rates for in­creas­ing their pro­duc­tiv­ity and eco­nomic re­turns.

Feed­ing of Nile tilapia breed­ers for con­di­tion­ing in a Calauan hatch­ery.

Hold­ing of Nile tilapia fin­ger­lings in net cages at a Calauan hatch­ery be­fore be­ing trans­ported to Batan­gas.

Har­vest­ing of sex-re­versed Nile tilapia fin­ger­lings at the MGB Aqua­farm.

Breed­ing ponds for Nile tilapia in a Calauan hatch­ery.

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