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TIGBAUAN, Iloilo – Not all leaves that fall to the ground are litters, there is one – the talisay leaves, that in its drying, it is sustaining a fish life.
A recent study has shown that the leaves of the common talisay (also known as the Indian or tropical almond tree) improved the survival of the larvae of ayungin, or silver therapon (Leiopotherapon plumbeus) a freshwater fish consumed by many Filipinos.
Southeast Asian Fisheries Development Center (SEAFDEC) scientist Dr. Frolan Aya conducted a study on how the the talisay leaves can help improve the survival and health of various aquatic species. His research proved that the talisay leaves, when added and allowed to decompose in fish culture tanks, resulted in a 48 percent survival of ayungin larvae whereas those without the leaf substrate only achieved a 27 percent survival rate.
Aya’s study co-authored by Vicar Stella Nillasca, Mary Jane Sayco, and Luis Maria Garcia was published this year in the 66th volume of the journal Ichthyological Research.
Acccording to their research,“aqueous extract of tropical almond leaves are known to contain tannins that enhance water quality by reducing pH and TAN (Total Ammonia Nitrogen) levels.” Further, other studies have shown that talisay leaf extracts also possess antimicrobial and antifungal properties due to the presence of an array of beneficial organic compounds.
Talisay is a common ornamental tree in the Philippines often planted in Philippine coastal communities. Its broad leaves in shades of yellow, orange and red fall and die away in summer and during the rainy season the leaves will turn a brilliant green once more.
Aya’s study showed that by simply littering hatchery tanks with talisay leaves allowed small organisms such as zooplankton and insect larvae, to colonize the leaf surfaces and these organisms soon became food for the ayungin larvae.
It might have also been possible, according to the study, that the accumulation of leaves at the tank bottom reduced water motion and allowed the larvae to conserve their energy instead of going against the flow of current.
The research suggested that the decomposing leaves caused the water to darken thus, “the darkening of the rearing lake water may also provide a good background or contrast for the larvae to efficiently capture its prey, thus contributing to better feeding success and consequently significantly improved larval survival in the present study.”
Previous studies have shown that the mere presence of leaf litter in culture tanks presents some advantages to improve fish survival. However, other studies using only extracts of the talisay leaf without the litter have shown significant improvements in the survival of fish and even tiger shrimp (Penaeus mondon).
SEAFDEC/Aquaculture Department said that placing dried talisay leaves in culture tanks appears to provide both the physical benefit of a leaf litter substrate as well as the leaching of desirable organic chemicals to the rearing water. While the method seems simple, more study is still needed, especially on new applications.
As a result of this study, SEAFDEC can now sweep away all the talisay leaves that litter its driveway to their hatcheries and laboratories to aid the aqualcuture industry.