Endangered Tawilis: The Population Trend of Sardinella tawilis and its Relation to Changes in Water Quality and Weather Patterns from 2010 to 2020
The Bachelor of Science in Environmental Science Program of the Department of Environmental Science invites all the members of the Loyola Schools community to the Thesis Defense of Mr. Miko Noel P. Mercado, Ms. Katreen Claire T. Paderes, and Ms. Danielle Theris C. Ravena on 2 May 2022 at 5:00 in the afternoon (online).
Mr. Mercado, Ms. Paderes, and Ms. Ravena's thesis entitled, “Endangered Tawilis: The Population Trend of Sardinella tawilis and its Relation to Changes in Water Quality and Weather Patterns from 2010 to 2020" will be presented to Ms. Sophia Angeli S.N. Dayrit, Mr. Raymond S. Rodolfo, and Dr. Rey Donne S. Papa. Their advisers are Dr. Milette U. Mendoza and Dr. Ma. Theresa Mutia.
Abstract
In the past 20 years Sardinella tawilis, an endemic and commercial fish in Lake Taal, is estimated to have a population decline of up to 50%, putting it on the IUCN Red List in 2018 as an endangered species. With this, we see a need to further look at the population data of S. tawilis to better gauge their state and develop more effective mitigation for the endemic species. ANOVA and Tukey HSD/Kramer Test was used to distinguish differences between the aquaculture sites and the open-fishing areas. With paired difference p-values (i.e., 0.032, 0.022, 0,732, and 0.882) we observed that the water temperature at the first 20 m of depth, pH, and nitrogen concentration levels were significantly different between aquaculture and open fishing sites from 2010 to 2020. A separate Principal Component Analysis (PCA) was performed to determine which of the water quality, and weather parameters most drive changes in the lake. PC1 was dominated by water transparency, followed by water temperature at 10 to 20 m and 0 to 10 m of depth, with eigenvalues of 0.46, -0.40, -0.39, respectively. Meanwhile, only wind speed (0.54), cloud visibility (0.54), and rainfall (-0.48) were significant in terms of weather patterns. From the correlation matrix, S. tawilis larvae were found to be positively correlated to dissolved oxygen (0.70), wind speed (0.34), and cloud visibility (0.23), while negatively correlated to water temperature at 10 to 20-meter depth (-0.52), water temperature at 0 to 10-meter depth (-0.42), rainfall (-0.51), and sulfide concentration (-0.42). To provide more accurate trends on the population of S. tawilis, we recommend continuous stock assessment, water quality monitoring to the various open-fishing sites, and look into how weather parameters can affect S. tawilis aside from water quality. Further studies may also look at the status of other species in connection to S. tawilis population trends to have a better understanding of the overall dynamics of this endemic species in the lake.
Keywords: water quality, weather, PCA, correlation matrix, S. tawilis behavior
For those who wish to join the oral presentation and defense, kindly get in touch with Dr. Milette U. Mendoza at mumendoza@ateneo.edu for the official Zoom link.
Thank you.