Flucatuating asymetry and blood biochemistry as stress biomarkers in openwater and aquaculture populations of Oreochromis niloticus (Nile tilapia) in Taal Lake, Batangas.

Abstract

Aquaculture is the method of breeding, rearing, and harvesting both marine and freshwater species and can range from land-based to open-ocean production. The concern of feeding the rapid-growing world population and contention of insuring food security has brought focus on aquaculture as one of the means to increase seafood yield and consequently, food production outputs. The industry has grown at a strong and steady 8-10% over the past three decades (WWF, 2011). World aquaculture is heavily dominated by the Asia–Pacific region, which accounts for 89% of production in terms of quantity and 77% in terms of value (FAO, 2011). The Philippines places 12th, globally, in aquaculture production (FAO, 2011).

The practice of aquaculture is vital to the country‟s economy in providing substantial employment and income, contributing export earnings and meeting demand for the food security of the populace. While there is a positive growth rate in production, the sector still needs to maintain a delicate balance between the requirements of increased production, contributing to food security, against the need to conserve and protect the aquaculture resource for long-term economic stability and environmental sustainability. Increased demand for tilapia has shifted many tilapia producers from subsistence growers to larger, export-driven producers, and this has been shown to create various environmental stresses.

Currently, unsustainable aquaculture practice is suspected of being the cause behind multiple fish kill events in the country, extending from Zamboanga, South Cotabato, Pangasinan and Batangas. According to the Department of Environment and Natural Resources (DENR) and the Bureau of Fisheries and Aquatic Resources (BFAR), 700 metric tons of milkfish and tilapia, worth approximately P57.226 million, have been killed in the different fish cages surrounding Taal Lake (Purificacion, 2011). Aquaculture development is faced with challenges relating to improving production efficiency whilst maintaining environmental integrity, as well as adapting to and mitigating the impacts of changes in climatic and environmental conditions. Moreover, as environmental and health concerns are constantly raised, there is a preeminent need for an efficient, reliable and economical means of biomonitoring stress levels of biota in aquaculture systems.