38 JUNE 2019 • WORLD AQUACULTURE • WWW.WAS.ORG area in 2002 (Ferrera et al. 2016). Eutrophication was largely the result of the over-abundance of fish farm structures, at twice the allowable number set by the local government. Impacts on biodiversity remain a concern, particularly where there is potential for invasive species being involved in disruption of ecosystem functions. Aquaculture sites in Laguna de Bay, the largest inland freshwater body in the Philippines, have significantly lower species richness, species evenness and relative dominance of native species (Cuvin-Aralar 2016). The SEAFDEC/AQD (2016) has four research and development programs related to biodiversity, including one that investigates the impact of aquaculture on the biodiversity of aquatic fauna near the Binangonan Freshwater Station. The three other programs involve ranching of seahorses and sea cucumbers, two of the most heavily exploited animal taxa in the illegal wildlife trade. Wildlife farming, which is the legal commercial domestication and breeding of traded organisms, has become popular in recent years among conservationists because of its potential to reduce pressure on wild populations of exploited fauna and flora (Tensen 2016). Seahorse and sea cucumber ranching done in the Philippines for purposes of supplying the trade, which is mostly for traditional Chinese medicine (Domínguez-Godino et al. 2015, Yasue et al. 2015), are examples of wildlife farming, although the term has not been used locally to describe such operations. The country has been recognized for large-scale rearing of the seahorse species Hippocampus kuda and H. trimaculatus, with novel set-ups involving floating bamboo and nylon mesh cages for grow-out of juveniles (Koldewey and Martin-Smith 2010). Ursua and Azuma (2016) report seahorse farming operations run by SEAFDEC/AQD have seen improvements in broodstock reproduction as well as in survival and growth of newborn and juvenile seahorses through ultraviolet sterilization of water and formalin treatment of feeds. The aquaculture industry may lend itself well to the wildlife farming model and contribute to a reduction of pressure on coral reefs from wild harvest of marine ornamentals. This is because of the existing capability for closed cycle systems for cultured species, general feasibility, and its being incentive driven; fisherfolk’s success in aquaculture will reduce their reliance on wild stocks. A financial feasibility analysis has shown that an integrated, fullcycle aquaculture system for the common clownfish Amphiprion ocellaris, a staple of the marine ornamental trade, can be profitable, although small-scale fisherfolk would need subsidies to meet the high initial capital investment and subsequent operating costs (Pomeroy and Balboa 2004). Disease Risks and Mitigation Diseases have long plagued aquaculture all over the world. In 2013, diseases were considered the most important challenge in global shrimp aquaculture (Anderson and Valderrama 2013). Tropical shrimp aquaculture may be in a crisis of lost production induced by diseases, with the major threats being white spot syndrome virus (WSSV), infectious hypodermal and hematopoietic necrosis virus, and early mortality syndrome, also known as acute hepatopancreatic necrosis disease (AHPND). Contrary to traditional views, Doyle (2015) has suggested that inbreeding among farmed shrimps has caused significant depression in their resistance to disease and climate stress and so biosecurity and genetic enhancement programs should be promoted. There are also reports of emerging diseases in local shrimp aquaculture, such as the abdominal segment deformity disease, that had previously been known only among cultured white shrimp Litopenaeus vannamei in Thailand (Santander-Avancena et al. 2017). Such problems are not limited to shrimps, of course. A study in Taal Lake by Hallare et al. (2016) showed significantly more micronuclei and nuclear abnormalities in Nile tilapia Oreochromis niloticus in aquaculture sites compared to non-aquaculture sites, perhaps due to un-ionized ammonia and copper in bottom sediments where tilapia feed. The concern over diseases in aquaculture persists, even as improvements to biosecurity continue to develop. In 2015, there were at least ten research and development programs by SEAFDEC/ AQD on monitoring, diagnosis, investigation, reduction and treatment of diseases across different finfish and shellfish species (SEAFDEC 2016; Table 2). In May 2015, the FAO began to fund a local project meant to raise awareness on and control of AHPND in farmed shrimp (FAO 2017; Table 3). Another project began in January 2017 with the objective of strengthening capacities, policies, and national action plans concerning aquatic antimicrobial resistance. Molecular Techniques for Improving Aquaculture Practices With the rise in ubiquity of molecular techniques in biological disciplines, aquaculture has also been increasingly turning to these tools to improve practices. DNA-based markers have been used to determine stock characteristics and monitor stock quality, including determining rates of inbreeding, identifying specific markers correlated with fitness and comparing wild and hatchery stocks (Romana-Eguia et al. 2015). In milkfish, microsatellite markers were developed from 24 loci (Santos et al. 2015). Of the 72 markers developed, nine showed high success rate in amplification and polymorphism. These markers can be used for genetic stock discrimination and monitoring. Molecular techniques also are used in the fight against diseases. Next-generation sequencing and suppression subtractive hybridization was used to find genes associated with higher survival rates against WSSV in shrimp (Maralit et al. 2014). Hemocyanin, Tilapia production tops all other freshwater systems in the country, making up more than 95 percent of the freshwater fish ponds. This photo shows a breeding pond for the improved Excel tilapia in BFAR, Nueva Ecija, Philippines (Photo: J.A. Ragaza).
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