Tawilis: Only in Taal Lake and nowhere else in the world
BY: ERROL A. GATUMBATO
TAAL VOLCANO PROTECTED LANDSCAPE, Batangas — The Taal Lake and Taal Volcano, both located in the province of Batangas and not in Tagaytay City, as commonly perceived, are two of the most popular landmarks in the Philippines. The active Taal Volcano is surrounded by the third largest lake in the country, and these two sites and adjoining areas have been declared as the Taal Volcano Protected Landscape. The TVPL has remarkable and unique features, its entire landscape is picturesque, and comparable to some of the world’s famous protected areas.
Taal Lake has an oval outline and measures 24,356 hectares, with a circumference of 120 kilometers, and a maximum depth of 198 meters. Its center is the 23.8 square kilometers Volcano Island, where at the middle of it lies the 1.9 kilometers crater lake, also known as the lake within the lake. More than its awesome and refreshing view, Taal Lake is a very important ecosystem, because it supports a good number of diverse fauna, comprised of both freshwater and marine species that are commercially important. But more than its economic relevance, Taal Lake is a biologically important site, since it is the only known area in the world for the freshwater sardine, locally known as “Tawilis” or scientifically described as Sardinella tawilis.
The entire biology of Tawilis is hardly known, but so far there are no available records attesting that this species is also occurring in
other freshwater ecosystems in the Philippines. However, the biological importance and conservation values of this endemic fish are not given full attention, since it is being commercially harvested in the area. A lot of fishers and many residents of Batangas, in general, are probably not aware that this species is only known to occur in Taal Lake and how valuable Tawilis is in the global biodiversity context.
The maximum size of Tawilis is only 15.2 centimeters and its maximum weight is 27.3 grams. According to the Bureau of Fisheries and Aquatic Resources Region IV-A, Tawilis is believed to have migrated from Balayan Bay to Taal Lake when the latter was formed by several volcanic eruptions hundreds of years ago. A freshwater fish expert named as a certain, Herre, described the species as Harengula tawilis, in 1927, but another expert known only as Wongratana re-described it in 1980 as Sardinella tawilis and listed Tawilis as one of 18 species of Sardinella in the Indo-Pacific Region. On the other hand, Whitehead in 1985 listed Tawilis as one of the 21 species of Sardinella worldwide and considered it as the only freshwater Sardinella, the BFAR report said.
Tawilis is the most commercially dominant fish catch in Taal Lake. It is mainly caught by gill net, beach seine, ring net and motorized push net. Reports of the BFAR claim the highest production of Tawilis was recorded in 1984, estimated at 29,000 metric tons followed by 8,798 metric tons in 1988. However, Tawilis production slowly declined from 744 metric tons in 1996 to 294 metric tons in 2000. The BFAR attributed the declining production of Tawilis to illegal operation of active fishing gear, like the motorized push net and ring net, overfishing, proliferation of fish cages and deterioration of water quality in the lake. The BFAR noted the issues affecting the declining production of Tawilis are serious, and may pose a grave threat not only to Tawilis production, but to the very existence of this Taal endemic fish.
Professor Gordon McGregor-Reid, Global chair of the IUCN-World Conservation Union Freshwater Fish Specialist Group, and at the same time the chief operating officer of the North of England Zoological Society or
Chester Zoo, who visited Taal Lake last week, opined the existence of Tawilis is seriously threatened. This is due to the presence of numerous introduced exotic species in Taal Lake, some which may likely predators of this species. He also said that other environmental factors, like the water quality and pollution from fish feeds in fish cages, are also noticeable. McGregor-Reid underscored the endemic status of Tawilis, being known to occur only in Taal Lake, and the issues facing its existence merit the designation of the species as conservation important, and possibly be listed in the threatened species of the world. However, the commercial importance of Tawilis may likely be a constraint for its classification as a threatened species.
(This Article also appeared at the Visayan Daily Star, 22 February 2010 issue, Bacolod City, Philippines)
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