Lake Taal's freshwater sardines Sardinella tawilis (Herre): Evolutionary insights based on morphological, molecular, and geological data
Share
Abstract
Sardines (family Clupeidae or herrings) are mostly marine species. In the Philippines, Lake Taal is the habitat of Sardinella tawilis (local name tawilis ), the only local endemic sardine species known to be fully adapted to a freshwater environment. Its evolutionary history is thus of great interest. So far, analyses of morphometric, meristic, isozyme, and mtDNA data point to the marine species Sardinella albella as the closest marine relative. Furthermore, mitochondrial DNA data revealed restricted substitution that may indicate either the beginning of a genetic differentiation of two tawilis sub-populations or the ghost of polymorphism past strengthened by genetic drift. Sardinella tawilis is believed to have emigrated from Balayan Bay to Lake Taal when it was formed in the course of volcanic eruptions some 240 years ago. The data do not, so far, support this contention. An alternative explanation on the speciation of this species is presented here.
Suggested Citation
Pagulayan, R. C. (2005). Lake Taal's freshwater sardines Sardinella tawilis (Herre): Evolutionary insights based on morphological, molecular, and geological data. In M. L. Cuvin-Aralar, R. S. Punongbayan, A. Santos-Borja, L. V. Castillo, E. V. Manalili, & M. M. Mendoza (Eds.), Proceedings of the First National Congress on Philippine Lakes (pp. 40-43). Southeast Asian Regional Center for Graduate Study and Research in Agriculture (SEARCA).
Type
Conference paperISSN
1656-8099Collections
- LakeCon2003 [49]
Related items
Showing items related by title, author, creator and subject.
-
Series: Summary of Proceedings No. 1/2013;
Seasonality, abundance and biology of tawilis (Sardinella tawilis) in Taal Lake, Batangas
(PCAARRD-DOST, 2013)A landed fish catch survey was conducted in ten landing centers around Taal Lake from June 2008 to May 2009. Fish catch and unit effort were recorded at 2 days interval for 10 days a month in the established sampling stations. Inventory of fisherfolk, boats, and gear was also conducted. A total of 300 'tawilis' samples per month were measured and dissected to determine the biological and population parameters. Results showed that there were 2,488 fisherfolk, 2,250 fishing boats, and 15,947 units of fishing gear recorded in Taal Lake. Tawilis production in the lake has declined. In 2009, tawilis production was 132 mt, a reduction of 82 % from the average production from 1996 to 2000. However, tawilis remained to be the most dominant fish in the open waters with about 36% of the total fish catch. The major gear used to catch tawilis were gill net and beach seine with catch per unit effort (CPUE) of 6 kg/day and 35 kg/day, respectively. There were 4,646 fish samples analyzed with an average fork length of 9.8 cm, average total length of 11.1 cm and an average weight of 13.2 g. The sex ratio obtained was 1 male to 0.85 female. Spawning of tawilis is all year round with highest gravid samples from March to May and November to December. Tawilis with an average fork length (FL) of 9.9 cm and weighs about 13.9 g has an estimated 4,848 eggs. The analysis of length frequency data has an estimated L8 of 16.8; K value of 0.59; total mortality (Z), 3.46; fishing mortality (F), 1.93; natural mortality (M), 1.54; and exploitation rate (E), 0.56. The fishing mortality was higher than the natural mortality and the exploitation rate exceeded the optimum 0.3-0.5 which implies that there is overfishing of tawilis in the lake. -
Translocation of the clupeid Sardinella tawilis to another lake in the Philippines: A proposal and ecological considerations
(Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources, 2001)The dwindling commercial catch of Sardinella tawilis (Clupeidae), locally known as 'tawilis', reported in recent years by local fisher folk in Lake Taal, Batangas, Philippines, could be a result of the interaction of factors such as over fishing, destructive fish-capture techniques, changes in water quality, and others. Like the rest of the handful of endemic freshwater fish species in the Philippines, S. tawilis is threatened with depletion of its stocks, if not with extinction in the near future. A conservation strategy that could be considered is the translocation of 'tawilis' to another lake in the Philippines, whose ecological features closely resemble those of Lake Taal and where 'tawilis' would receive socio-economic and cultural acceptability. Cases of clupeid introductions - natural and man-made, successes and failures - are presented from published literature. Special attention is given to the case of a well-planned trans-country (Thailand-to-Indonesia) attempt to introduce a clupeid fish. The broader questions of biodiversity, endemicity, conservation, and fish community structure in Lake Taal (and elsewhere) must be underpinned by sound basic taxonomy and ecology. -
Zooplankton diversity in Philippine Lakes
(Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development (PCAMRD), Department of Science and Technology; Bureau of Fisheries and Aquatic Resources, 2001)Sustainable fisheries development partly depends on the availability of adequate zooplankton as principal food items of early life history stages of economically important fish species as well as of the adults of some species such as clupeids (e.g., Sardinella tawilis of Lake Taal in Batangas). The broad characteristics of the composition of freshwater zooplankton (Rotifera, Cladocera and Copepoda) of natural and man-made lakes in the Philippines are compared with those of the Oriental Region, in particular, and other tropical regions, in general. Two species of calanoid copepods are endemic, a somewhat remarkable occurrence considering that calanoids are represented by only five known species in the Philippines and absent in many large tropical lakes. Daphnia, which almost invariably influences food-web interactions and structures of plankton communities in temperate lakes, still has to be recorded.
