Tawilis, sinarapan, other Phl fish species threatened - studies

MANILA, Philippines - Tawilis, the world’s only freshwater sardine found solely in Taal Lake.

Sinarapan, the world’s smallest commercial fish species endemic (naturally occurring) to Lake Buhi in Buhi, Camarines Sur.

Kansusuwit (half-beak fish), papalo, banguynguy, and other indigenous species that felt at home in the once clean and clear waters of Laguna de Bay.

Once upon a time, these and other prized fish species thrived in Philippine lakes—and placed the country on the global fisheries map.

Now, their populations are dangerously declining owing to a variety of anthropogenic (man-caused) factors, among them overexploitation, introduction of omnivorous (one that feeds on both animals and plants) and “invasive” fish species, and environmental problems such as pollution.

For instance, tawilis (scientific name: Sardinella tawilis) once was the most dominant and commercially important fishery of the 26,000-hectare Taal Lake in Batangas province, the country’s fourth largest inland body of water which was the site of recent “fish kills”.

“Tawilis production in the lake has declined,” attested a joint study done by Maria Theresa Mutia, Myla Muyot, and Charice Faminialagao of the National Fisheries Biological Center (NFBC) in Taal and Francisco Torres of the Department of Agriculture-Bureau of Fisheries and Aquatic Resources-National Fisheries Research and Development Institute (DA-BFAR-NFRDI).

The three presented the results of their research, titled: ”Seasonality, Abundance, and Biology of Sardinella tawilis”, at the Second National Congress on Philippine Lakes (LakeCon 2011) held recently at the Southeast Asian Regional Center for Graduate Study and Research in Agriculture (SEARCA) on the University of the Philippines Los Baños (UPLB) campus in Los Baños, Laguna.

The NFBC/NFRDI researchers noted that the highest catch of tawilis in Taal Lake was 1,120 tons in 1998. In 2009, tawilis production had precipitously dropped to only l32 tons, a reduction of 88 percent from that of 1998.

The severe depletion of tawilis catch in the now degraded Taal Lake was also confirmed in a joint study by Mudjekeewis Dalisay Santos of NFRDI and Demian Alexander Willette of the Old Dominion University in Virginia, USA.

They also presented their findings at LakeCon 2011, which was sponsored by SEARCA headed by Director Gil C. Saguiguit Jr. and the Los Baños-based Department of Science and Technology-Philippine Council for Aquatic and Marine Research and Development (DOST-PCAMRD) headed by OIC Executive Director Cesar Pagdilao.

As an offshoot of their study, Santos and Willette proposed a management strategy that demarcates a new fish sanctuary in Taal Lake to help save the tawilis.

“We suggest that a closed season be considered as an alternative strategy in managing the world’s only freshwater sardine fishery,” they stressed.

Sinarapan (scientific name: Mistichthys luzonensis) is known internationally as the world’s smallest commercial fish species. Now, this “Lilliputian” goby is in danger of extinction in view of the introduction of tilapia and the grave pollution facing the 1,707-ha lake situated about 500 kilometers southeast of Manila.

For instance, there was a time when almost 80 percent of the lake was covered by about 16,000 fish pens, which is in violation of the Philippine Fisheries Code which stipulates that only 10 percent of a lake should be devoted to fish pen production to maintain the water quality and minimize pollution problems.

As found in a SEARCA-supported study done by the Central Bicol State University of Agriculture (CBSUA), the fish cage operators used about 2,840 ton of feeds per production cycle (about four months) to maintain their fish stocks.

The unused feeds that settled in the bottom added to the lake’s already grave pollution problems brought about by the dumping of human and animal wastes into the lake by people living around it.

Thus, fish kills have become regular occurrences in the now shallow and shrinking Lake Buhi. Last year alone, two fish “drowning” incidents took place.

As the SEARCA-assisted CBSUA study warned: “The declining productivity trend and near loss of sinarapan already indicate the system’s difficulties in recovering from ecological stresses. Overcrowding of fish cages, excessive artificial feeding, and sedimentation tend to compound the problem.”

Fish kills have also become common occurrences in Laguna de Bay, the country’s largest (91,000 ha) freshwater lake.

About four decades ago, 23 fish species thrived in the lake’s then clean and clear waters, reported a research done by a certain Pruginin, as cited by a BFAR study.

Today, only about a dozen species have survived the lake’s now heavily polluted and silted waters, surmised Eduardo Manalili of PCAMRD and Eunice Villanueva and Zenaida Fontanilla of the BFAR-Freshwater Fisheries Research Station in Los Baños.

Disturbingly, too, some of the surviving species are threatened with extinction.

Milkfish and tilapia have long been commercially raised in Laguna Lake.

In the mid-1990s, Manalili reported, some 150,000 tons of tilapia were harvested annually, providing about three-fourths of Metro Manila’s freshwater fish needs. Productivity of tilapia, however, has subsequently declined.

Milkfish production in fish pens also eventually occupied much of the already choking and dying Laguna de Bay.

Villanueva and Fontanilla noted that fish species still found in the lake are mudfish (dalag)), catfish (hito), carp. eel, kanduli, ayungin, gurami, shrimp, dulong, papalo, banguynguy, and kansusuwit.

But many of the native species could hardly be seen anymore, they lamented.

Aggravating the lake’s problem is the introduction of “invasive” species. For instance, PCAMRD noted, the omnivorous janitor fish has become part of the lake ecosystem, contributing to the depopulation of the small fish species.

Another threat to the indigenous species in Laguna Lake is the African hito, which was introduced in the country years back. Rudy A. Fernandez