Abundance and distribution of Sardinella tawilis (Herre, 1927) larvae in Lake Taal, Philippines

Abstract

As part of the conservation efforts to address the declining population of the only freshwater Sardinella (Family Clupeidae) endemic to Lake Taal, a two-year study was conducted to determine the possible spawning grounds of Sardinella tawilis (Herre, 1927) by identifying the spatial and temporal distribution of its larvae. Fish larval samples were sorted from ichthyoplankton samples collected monthly in selected sampling stations in the lake. The morphologically identified Clupeidae larvae were determined to be S. tawilis genetically. They appeared only during March to May, with maximum abundance reaching from 700 to 1,700 ind 100m-3 during April 2015. Among the 10 water, 5 weather, and 11 biological parameters analyzed using Redundancy Analysis (RDA), temperature and other weather parameters largely influenced the temporal distribution of tawilis larvae. In terms of spatial distribution, the stations on the eastern bay of the lake showed an abundant and consistent presence of tawilis larvae for two years. Other stations which showed the presence of tawilis larvae include the southern portion of the lake, as well as in stations south to southwest area of Volcano Island. The seasonal and site-specific occurrence of tawilis larvae confirmed its spawning season and potential spawning grounds, which can serve as a scientific basis in the establishment of a Tawilis Reserve Area, as stipulated in the Unified Rules and Regulations for Fisheries in the Taal Volcano Protected Landscape Management Plan (TVPL-MP 2011).

Supply and Value Chain Analysis of Freshwater Sardine, Sardinella tawilis (Herre 1927), in Taal Lake, Batangas, Philippines

“…Sixty-eight percent (68%) of the respondents do not have other sources of income except fishing. Peak fishing season is during March, April, and May, which coincides with the spawning season of tawilis (Mutia et al 2018b). The majority of the head of the family (father) are the respondents.…”

“…ardinella tawilis is the only freshwater species under the genus Sardinella endemic to Taal Lake, Batangas, Philippines (Wongratana 1980;Whitehead 1985;Mutia 2011;Mutia et al 2018a;Mutia et al 2018b). It is locally known as tawilis that belongs to the family Clupeidae and one of the most commercially important fish species in Taal Lake's inland fisheries (Almazan et al 2011;Mutia et al 2011, Mutia et al 2018b. S. tawilis was identified as a sister species of the Taiwanese marine sardinella, Sardinella hualiensis, due to morphological similarity (Willette et al 2014).…”

“…However, its production declined from 744 MT in 1996 to 71 MT in 2011 with a high exploitation rate from 0.52 to 0.65, indicating unsustainable fishing practices. This is mainly due to several factors such as illegal use of active fishing gear, proliferation of alien fish species, and increasing pollution load contributed by improper aquaculture practices (Mutia et al 2011;Mutia et al 2018a;Mutia et al 2018b). The International Union for Conservation of Nature (IUCN) has assessed the Sardinella tawilis as an "endangered" species due to the continuing decline in the number of mature individuals and the estimated harvest declined by 49% over the past 10 years (Santos et al 2018).…”

“…The International Union for Conservation of Nature (IUCN) has assessed the Sardinella tawilis as an "endangered" species due to the continuing decline in the number of mature individuals and the estimated harvest declined by 49% over the past 10 years (Santos et al 2018). Several biological studies have been conducted by researchers (Magsino 2012;Mutia et al 2018a;Mutia et al 2018b;Papa et al 2008;Quilang et al 2011) to conserve and manage this species. Almazan did the potential impact of contracts on the sustainability of the bottled tawilis supply chain in 2011.…”

First Successful Transport and Short-term Rearing of the Endangered Sardinella tawilis (Herre, 1927) in Ex Situ Captivity

“…tawilis is one of the most economically important freshwater resources in Taal Lake sought after by both locals and tourists. The fish is traditionally caught with beach seines and gillnets, although illegal fishing gear such as trawl nets, motorized push nets, and the use of "superlight" have also been used (Mutia et al 2004(Mutia et al , 2018. Due to its endemicity and popularity to tourists as local cuisine, S. tawilis are in high demand and sold at a higher price than their marine counterparts.…”