World Aquacluture Magazine - September 2020

WWW.WA S.ORG • WORLD AQUACULTURE • SEP TEMBER 2020 37 ( C O N T I N U E D O N P A G E 3 8 ) Challenges inCultivatingMilkfish Unlike tilapia, there is not much known about the negative effects of milkfish on ecosystems. So far, no studies have been conducted to evaluate environmental impacts. The tracking of milkfish from its introduction through its lifetime can be very challenging because the range of this species is transnational, requiring study of its behavior and movement. For instance, the adaptability of milkfish to various diets and environment is disadvantageous for some endemic species (Bagarinao 1994). Milkfish is highly resistant to parasites and diseases, although, like many fish species, they can be prone to a wide range of diseases when they are stocked at high densities or stressed for a long duration. Hence, thorough monitoring is needed in ensuring quality and carrying capacity. This can also prevent deterioration as well as other problems brought by mismanaged aquaculture (Joshi 2005). Carp In 1915, common carp Crypinis carpio was first introduced to the Philippines fromHong Kong, followed by later introductions of other carp species. Since then, it has become one of the most stable food sources of Filipinos (Guerrero 2014). Bighead carp Aristichthys nobilis is one of the most cultivated fish in the fish pens of Laguna Bay (Cuvin-Aralar 2016), where it is normally grown in polyculture with tilapia and milkfish (SEAFDEC 2019). Culture of this species has largely replaced freshwater milkfish culture in Laguna (Yap 2002). Bighead carp has a fast growth rate reaching marketable size of 2-4 kg in about 4-6 mo (SEAFDEC 2019). They are primarily filter feeders but adults generally feed on phytoplankton and zooplankton. Larvae and juveniles of this fish feed on zooplankton. Opportunities inCarpAquaculture Common carp is also very important in the local aquaculture industry, although many Filipinos find it unpalatable. Its low protein requirement in diets make it ideal for aquaculture. Bighead carp also grows fast, so harvest is usually abundant. Moreover, bighead carp have high resistance to diseases so disease control is not necessary in extensive to semi-extensive culture systems (SPC 2011). Stocking this fish in water bodies supports commercial fisheries because it increases the total biomass available for harvest (SPC 2011). Stocking of bighead carp has been used in some Pacific countries that have poor freshwater fauna (Kolar et al. 2007). It can also be used in reservoirs with high nutrient content for biological control of eutrophication. As bighead carp are highly adaptable to available food, artificial feeds are not necessary. A study made on tilapia and carp species in mainland Southeast Asia supported substantial increase in biomass fish harvest with only mild impacts on native sh communities (Arthur et al. 2010). The careful introduction of bighead carp can enhance the supply of freshwater fish, thus contributing to overall economic growth. Challenges inCultivatingCarp Carps are filter feeders and may compete with native species for the same food resources. Because of its ease in establishing a population in newly inhabited environments, its biomass can grow greater than that of native species that occupy the same niche in the ecosystem. Bighead carp can survive and establish its population in the Great Lakes even with a few adults as a starting population, competing with native fishes for food and space (Cudmore et al. 2012, Cuddington et al. 2014). Diets of native planktivorous bigmouth buffalo and gizzard shad overlap with the bighead and silver carp, resulting in decreased fecundity and deteriorated body condition in the two native species (Irons et al. 2007). In the United States, bighead carp and silver carp are considered to be highly invasive. These AIS were initially used as a biological control for plankton and to improve water quality in aquaculture and sewage treatment plants but ended up invading the Mississippi River (Kolar et al. 2007). To date, NewYork State and other cities in Canada have banned the sale of this fish. Fines were also imposed by the OntarioMinistry of Natural Resources, but despite this, underground selling of this fish persists (Toronto Breaking News 2015). The BASIL Program The BASIL program is an enhancement of the National Inland Fisheries Enhancement Program to address the deficiency in fish supply in lakes, rivers and reservoirs in upland and landlocked areas (Philippine News Agency 2017, Beñas 2018). The programwas formed to address the growing demand for fresh fish consumption in the Philippines and revitalize the Philippine aquaculture industry. It intends to provide increased fish protein to the Filipino diet and livelihood options and employment opportunities for stakeholders (Flora 2017). Tilapia and milkfish are the most popular food fish in the Philippines, although these fishes are considered invasive species (Photo: A.G. Wyson). Carps are characterized by their fast growth rate, reaching marketable size of 2-4 kg in just 4-6 months (Photo: E.V. Morata, Sr.).