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Genetically improved tilapia to ease fish supply?

By RODEL G. OFFEMARIA

ANOTHER strain of a genetically improved tilapia may have unlocked new possibilities for the country's depleted fish resources under continuing pressure from an exploding 2.1 population growth rate. Zosipat Beniga of the Mindanao State University successfully improved the genetic composition of Nile tilapia (Oreochromis niloticus) resulting to a significantly high 96.6% and 94.2% survival rate in cultured environment.

The study was done in floating net cages measuring four-square meters wide and 2.5 meters deep off Lake Sebu in Cotabato stocked with the experimental genetically improved farmed tilapia (GIFT), genetically male tilapia (GMT), and a selected line of tilapia species including locally produced commercial strains.

Each floating cage was stocked with 120 different tilapia strains at random and fed with commercial fish feeds for 84 days. By the end of the culture period, Beniga found that the selected line of tilapia grew at a daily rate of 0.94 grams and had the highest mean weight of 82 g. Meanwhile, the GMT, GIFT, and the local strains posted final mean weights in grams of 69.3, 67.3, and 58.1 while pegging daily growth rates of 0.78, 0.76, and 0.65, respectively. The selected line of tilapia species recorded a survival rate of 85.3%.

"The differences in survival rates are statistically significant" and may become strong considerations for future investment preference, said executive director Rafael Guerrero Ill of the Philippine Council of Aquatic and Marine Research and Development, an agency of the Department of Science and Technology based in Los Baños.

"Water quality parameters like temperature and dissolved oxygen in Lake Sebu are within optimum range" which means the lake is suitable for tilapia fishfarming, Guerrero Ill added.

Beniga's study also showed production cost of GMT is lowest at only P18.50 per kilo while posting the highest net return of 35.1 percent compared to the selected tilapia strains (P19.55 and 28.1%), GIFT (P20.05 and 24.5%), and locally grown tilapia (P22.96 and 8.8%). The PCAMRD-funded study also confirmed similar earlier studies that showed genetically improved tilapia perform significantly better than widely produced commercial counterparts.

Meanwhile, Dan Baliao of the Southeast Asian Fisheries Development Center based in Iloilo said recent studies in milkfish (Chanos chanos) fry production showed an encouraging 96.5 to 99 percent survival rates in brackish water ponds for a culture span of 60 to 105 days, the highest so far on the local scene.

Under close watch, the studies mainly conducted in Western Visayas also showed that the growth of hatchery-bred milkfish fry is faster than those found in the wilds, the traditional source of local producers.

The advances in local hatchery fry production technology, Baliao said, will mean less dependence to imports and cut pressure to the declining natural population of milkfish broodstock or sabalos.

In all, 50% of the country's tilapia production is grown mainly in freshwater cages and ponds while cage system in lakes and reservoirs account for 36%, Guerrero disclosed.

Tilapia production recorded a healthy 28% increase from 1986 to 1995 with the bulk coming from traditionally strong aquaculture areas of Ilocos, Central Luzon, and Southern Tagalog regions.

In 1995, overall tilapia production dipped to 102,426 metric tons, from the previous year's 115,863 MT, and a high of 120,294 MT in 1993, data from the Bureau of Agricultural Statistics showed.

On the other hand, milkfish, which is also widely produced in Ilocos, Central Luzon, Southern Tagalog, Western Visayas and Western Mindanao, declined 14% from i986 to 1995 because of continuing fry shortage and the massive shift to shrimp production in the 80s. Milkfish production is down to a low 158,357 MT in 1995, slightly trimmer from the 161,498 MT recorded in 1994, but far below the 184,910 MT achieved in 1986, BAS data showed.

Both tilapia and milkfish are sold in local markets with minimal

volume in frozen and fillet forms shipped out to mostly Filipino

communities in the US and Canada, Guerrero said.

Tilapia and milkfish, along with shrimps, oysters and mussels, comprise 40% of the country's total aquaculture production, a sector now consistently dominated by the highly profitable seaweed (Eucheuma

Kappaphycus) which is processed into carrageenan for industrial

application.

The Philippines is the world's fifth largest aquaculture-producing country with 1996 total output of 980,857 MT, or 35% of the fishery sector's national production valued at P33.21 billion.

Aquaculture's 1996 contribution to the fishery sector, aside form

providing "direct employment and income to over 250,000 Filipinos and

their families" outpaces for the first time in history those of commercial (33%) and municipal (32%) fishing, Guerrero noted. S&T Media Service

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