Malacofaunal research in a karst ecosystem is very limited not only in the northern region of Luzon Island but in the entire Philippines amidst extensive habitat disturbance and destruction. To address this, the diversity and abundance of land snails in the karst areas of Santa Teresita, Cagayan Province were determined. A total of 25 5 x 5 m2 quadrats were randomly set in five stations in the karst landscape. A total of 1206 land snails comprising 45 species under 36 genera representing 17 families were sampled. Camaenidae was the most represented family with 10 species. Luzonocoptis antennae constituted 25.1% of the total number of samples (303 individuals) and was the most abundant species in all stations. Of the 36 genera, five are new records in the Philippines. Several karst endemics and introduced species were recorded. Diversity indices showed diverse land snail fauna with Shannon-Weiner diversity index (H’) of 2.80, with evenness (J’) of 0.36 and dominance index of (D’) of 0.11. Species accumulation curve (SAC) showed late asymptote with a completeness ratio of 0.92. The study demonstrated that land snails in Sta. Teresita, Cagayan Province are rich and diverse. It is very important to recognize Sta. Teresita as priority sites for malacofaunal conservation, and consider the further evaluation of these sites to be designated as a protected area.

The Taal Lake endemic freshwater sardine Sardinella tawilis (Herre, 1927), an important fisheries species, has been recently placed in the Endangered category by the International Union for Conservation of Nature due to its high endemicity and population declines, coupled with potential threats from natural volcanic and geologic events. We examined the survivorship of S. tawilis in short-term ex situ captivity (~ 30 d) and determined water quality parameters that influence survival. Collection, transport, and ex situ captivity trials for a total of 333 S. tawilis individuals were conducted from February–May 2021. The survival rate ranged from 2.6–26.9% after 30 d across the four trials. Principal component analyses showed that salinity, conductivity, and dissolved oxygen (DO) influenced S. tawilis survival. Generalized linear mixed models revealed that the combination of conductivity and DO have a significant effect on survival. Manifestations of handling stress observed in captive individuals include scale loss, hemorrhaging at fin base, swelling of eyes, and possible fungal infections. This study documents the first attempt at rearing S. tawilis via ex situ captivity. The findings of this study will serve as a basis to improve the survival of S. tawilis in captivity and will open possibilities of captive breeding or larval rearing for this endemic freshwater sardine.

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Reproductive biology is important in formulating management interventions for fish stocks. Limits on catch size are established based on the identified size at first sexual maturity of the target fish species, which can be accurately determined through histological analysis of gonads. The study investigated the reproductive characteristics of the endangered Sardinella tawilis and determined the size at first sexual maturity based on histological analysis. Between 2017 and 2018, 312 fish samples with different lengths were collected in Taal Lake's northern and southern basins. The length-weight relationship of S. tawilis shows that the species exhibits negative allometric growth. Female S. tawilis, characterized by larger sizes, are significantly more abundant in our catches than male individuals (mean sex ratio p<0.05) and exhibit an asynchronous oocyte development. Histological analysis of gonads showed that the size at sexual maturity for both male and female S. tawilis were at 75 to 79 mm FL, which was smaller than the reported size at sexual maturity based on morphological analysis. Smaller average and maximum lengths, as well as the size at first sexual maturity, could suggest that S. tawilis has experienced growth overfishing and a slowly degrading lake environment through time. Results highlighted the importance of ensuring that immature S. tawilis can enter sexual maturity and contribute to the population through reproduction. It is also highly recommended that the size of S. tawilis to be targeted by fisheries are individuals above 100 mm FL, which exhibited the highest proportion of spawning capable individuals.

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