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UPLB study seeks to ensure tawilis survival in case of massive Taal eruption

Gaea Katreena Cabico (Philstar.com) - March 16, 2021 - 5:11pm

MANILA, Philippines — When Taal Volcano, one of the country’s most active, erupted in January 2020, it disrupted the lives of thousands. It also raised concerns that a bigger explosion would lead to the decimation of tawilis, the only freshwater sardine in the world.

To prevent that grim prospect, scientists from the University of the Philippines Los Baños-Limnological Station in Laguna embarked on a mission to keep tawilis alive away from Taal Lake in Batangas, the only home of the endemic species.

The research project, which involved rearing the freshwater sardine ex situ or away from its natural environment, has been dubbed a breakthrough.

“The mere act of collection, transporting, and initially rearing tawilis alive is a major research breakthrough due to their highly sensitive characteristic,” Dr. Ma. Vivian Camacho, station manager of the UPLB-Limnological Station, said in an interview with Philstar.com.

To date, there are two batches of live tawilis kept at the UPLB-Limnological Station in Barangay Mayondon in Los Baños. The first batch of tawilis has stayed alive for nearly a month, while the second batch has been kept for two weeks.

Endangered sardine

In 2018, the International Union for Conservation of Nature listed tawilis endangered. 

According to the assessment, the harvest of the species has been declining since 1998 due to wanton fishing, illegal use of active fishing gears, proliferation of fish cages, and deterioration of water quality in the lake.

Several measures such as closed season for tawilis fishing, prohibition on the use of illegal fishing gears, and creation of reserve areas were implemented to allow the freshwater sardine to reproduce and replenish new stocks.

But a bigger threat remains: a massive volcanic event that could lead to the possible decimation of the species.

Hence, the volcanic unrest last year prompted scientists to conduct a research project which aims to save tawilis from possible extinction should there be a huge eruption.

Last week, state volcanologists raised the status of Taal Volcano in Batangas to Alert Level 2 as it has been exhibiting “increasing unrest.” The raising of alert level means “there is probable magmatic activity that may or may not lead to an eruption.”

“This project is very timely and important since in case of a massive, abortive explosion of Taal Volcano, keeping tawilis off-site will ensure continuous survival of their lineage,” said Camacho, who is also an associate professor at the UPLB-Institute of Biological Sciences.

How to travel with tawilis

There were previous attempts to collect, transport and rear tawilis off-site but all of them failed.

So how did scientists from UPLB manage to keep tawilis alive in captivity? Camacho said they interviewed fisherfolk on methods of catching tawilis and its behavior during collection.

“According to them, tawilis immediately die as soon as they are lifted with a net and kept out of water… From there, we thought of ways of improving their survival by exploring other methods of collection (type of net) with some modifications, proper handling during collection and transport, and maintaining optimal water quality,” Camacho said.

“In addition, a suitable culture tank, good water quality management and appropriate or suitable live feed during initial rearing are necessary to keep them alive,” she added.

The research called “FISH ARK Project for Taal Lake: Direction for conservation of the endemic freshwater fish Sardinella tawilis” is funded by the Department of Science and Technology-Philippine Council for Agriculture, Aquatic and Natural Resources.

Challenges

But scientists are constantly facing challenges in rearing tawilis away from its natural environment.

Increasing the survival rate of tawilis in captivity is the major challenge.

“Decline in the number of tawilis survivors is primarily due to diseases, post-transport stress and fluctuations or abrupt changes in water quality and other environmental conditions,” Camacho said.

She added they are in the process of “refining” protocols for collection, transport and initial rearing to ensure high survival.

Camacho said the ultimate goal, although it is not one of the objectives of the project, is to breed tawilis in captivity at the UPLB Limnological Station.

“This might be a long shot, but it is worth trying given the huge impact this research will have in terms of conservation of the endemic and endangered tawilis, especially now that Alert Level 2 has been raised over Taal Volcano,” she said. 

TAAL LAKE TAAL VOLCANO TAWILIS
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