Sardinella tawilis

Sardinella tawilis (the freshwater sardinella, freshwater herring, or bombon sardine), is a freshwater sardine found exclusively in the Philippines. It is the only member of the genus Sardinella known to exist entirely in fresh water.[1] Locally, they are known in Filipino as tawilis.[1]

Freshwater sardinella
Sardinella tawilis being sold in a market.
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Actinopterygii
Order:
Clupeiformes
Family:
Clupeidae
Genus:
Sardinella
Species:
S. tawilis
Binomial name
Sardinella tawilis
(Herre, 1927)
Synonyms

Harengula tawilis Herre, 1927

S. tawilis is listed in the Ark of Taste international catalogue of endangered heritage foods of the Philippines by the Slow Food movement.[2]

In January 2019, the International Union for Conservation of Nature declared S. tawilis an endangered species.[3][4][5]

Description

S. tawilis is a small fish reaching up to 15 cm and weighing less than 30 g. Like other members of their family, they have laterally compressed bodies with bellies covered in tough, scale-like scutes. They have a single, triangular dorsal fin and a forked caudal fin. They possess long, slender gill rakers in their mouths.[1]

Range and distribution

S. tawilis populations are only found in Taal Lake in Batangas province on the island of Luzon in the Philippines. The third-largest lake in the Philippines is in the caldera of an ancient volcano.[6] Before recent history, the lake was but an extension of the entirely marine Balayan Bay. Major eruptions in the 18th century essentially sealed the lake from the sea, eventually leading its waters to become fresh water. S. tawilis is believed to be one of a few former marine species trapped within the lake that have evolved into purely freshwater species.[1]

Ecology

S. tawilis, like members of its family, is an epipelagic filter feeder, using its gill rakers to strain plankton from the water while it swims with its mouth open. They roam the lake in large schools, just below the surface as the volcanic (and thus sedimentary) nature of the lake limits their plankton food to the surface.

The freshwater sardinella prefers to ingest larger prey, such as adult copepods, supplemented with rotifers and water fleas. During the summer months when the density of smaller copepods were much higher, their stomach contents consisted primarily of calanoid copepods, which are larger than the copepods blooming during this time. This suggests some partial control over prey selection exhibited by the fish, as opposed to simple filter-feeding.[7]

Little is known about their reproduction.[8] It is known that the Taal population spawns during the months of April to July, when surface temperatures are highest.[7]

Etymology and taxonomic history

Sardinella is the diminutive of the Greek sarda, meaning literally "little sardine".

The species was originally identified and named in 1927 as Harengula tawilis by Albert William Herre, the Chief of the Fisheries Division of the Bureau of Science in Manila. The species was later moved to the more appropriate and taxonomically accurate genus, Sardinella.[1]

Importance to humans
Bins of S. tawilis for sale at a Metro Manila supermarket

Despite its threatened status,[9] stocks in Lake Taal have been commercially fished for several decades. The fish is a widely popular food fish in the Philippines, and tons are shipped to most of the major cities in the country. Local supermarkets and wet markets usually have a tray or pile dedicated solely to the species.

The species is commonly referred to as tawilis in the local language of Tagalog. On the island of Cebu, one of the many places where tawilis is shipped, the native Cebuano name for the fish is tunsoy.[1]

In addition to raw consumption, tawilis is also processed into various food products. It is one of the many fish species dried, salted, and sold as daing in the country. They are also smoked and bottled in oil, and sold commercially.

In literature, Jose Rizal used three dried tawilis in his novel Noli Me Tangere to symbolize the Three Martyred Priests of Bagumbayan (Jose Burgos, Jacinto Zamora and Mariano Gómez).

Conservation

Because of several factors, the species is threatened by overfishing. As with all species consisting of a single population in one location, a local extinction event will lead to species extinction. As the population of the Philippines grows, the demand will be greater for tawilis, possibly overfishing the lake's stock population. According to the IUCN Red List report which conducted last February 28, 2017 and published in 2018, the catch of the tawilis started to decline since 1998 due to overfishing, illegal use of active fishing gears, increasing use of fish cages, and the deterioration of the water quality in Taal Lake. The harvest of the tawilis has said to declined by at least 50 percent over the past 10 years. Because of this, the IUCN listed the tawilis as endangered.[3][4][5]

References
  • "Sardinella tawilis". Integrated Taxonomic Information System. Retrieved 7 January 2007.
  • Whitehead, Peter J.P. (1985). "FAO species catalogue. Vol. 7. Clupeoid fishes of the world (suborder Clupeioidei). An annotated and illustrated catalogue of the herrings, sardines, pilchards, sprats, shads, anchovies and wolf-herrings. Part 1 - Chirocentridae, Clupeidae and Pristigasteridae". FAO Fisheries Synopsis. Rome, Italy: Food and Agriculture Organization of the United Nations. 125 (7/1): 1–303. ISBN 92-5-102340-9.
  1. Froese, Rainer, and Daniel Pauly, eds. (2010). Sardinella tawilis in FishBase. November 2010 version.
  2. "Tawilis". Slow Food Foundation for Biodiversity. Retrieved 19 December 2018.
  3. Jazul, Noreen (24 January 2019). "'Tawilis' now an endangered species". Manila Bulletin. Retrieved 24 January 2019.
  4. "Taal Lake's Tawilis now on list of endangered species". CNN Philippines. 24 January 2019. Retrieved 24 January 2019.
  5. "Isdang tawilis, endangered species na" (in Filipino). ABS-CBN News. 23 January 2019. Retrieved 24 January 2019.
  6. "A Decade Volcano". A Homepage for Taal Volcano. Retrieved on 2011-02-10.
  7. Papa, Rey Donne S.; Roberto C. Pagulayan; Alicia Ely J. Pagulayan (2008). "Zooplanktivory in the Endemic Freshwater Sardine, Sardinella tawilis (Herre 1927) of Taal Lake, the Philippines" (PDF). Zoological Studies. Taipei, Taiwan: Academia Sinica. 47 (5): 535–543. Retrieved 26 December 2008.
  8. Castillo, B.B.; A.S. Castillo; C.L. Gonzales (1975). "Tawilis fishery resources investigation of Taal Lake.". Philippine Council for Agriculture and Resources Research Fisheries Forum. Los Baños, Laguna, Philippines: Philippine Council for Agriculture and Resources Research. pp. 75–98.
  9. (2010_11). "Sardinella Tawilis, Philippine Information". FishBase. Retrieved on 2011-02-10.
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