Tawilis

Tawilis is a popular delicacy offered in many restaurants in Tagaytay City. What is a Tawilis? It is a freshwater sardine.

From Wikipedia:

Sardinella tawilis (sometimes obscurely referred to as the freshwater sardinella) is a freshwater sardine found exclusively in the Philippines. It is unique in that it is the only member of the family Clupeidae that is known to exist entirely in freshwater. Locally, they are known in Filipino as tawilis.

Tawilis populations are found only in a single lake on the island of Luzon in the Philippines. Taal Lake, a large body of water in the province of Batangas that used to be the caldera of an ancient volcano. Before recent history, the lake was but an extension of the entirely-marine Balayan Bay. A major eruption in the 16th century essentially sealed the lake from the sea, eventually leading to its waters becoming non-saline. Sardinella tawilis is believed to be one of a few formerly-marine species trapped within the lake that have evolved into purely freshwater species.