World Aquaculture December 2020

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2020 61 Tilapia Research and Development in the Philippines There has been constant improvement in different aspects of tilapia aquaculture in response to meeting local and global demands and maintaining profitability. Monosex production leads to better fish yield (El-Sayed 2006, Chakraborty and Samir 2009, Karim et al. 2017). Gamete production and behavioral interactions are monitored, leading to better growth performance. Several approaches have been used to produce monosex tilapia, especially hormonal sex reversal and production of genetically male tilapia (GMT) with YY genotypes. In 1997, farm trials compared the fish yield of GMT cultures with normal mixed-sex tilapia (MST) and hormonally sex-reversed tilapia (SRT) (Mair et al . 1997). GMT, MST, SRT and normal tilapia were cultured in tanks, ponds and cages. All fish were matched for age and size before acclimation to farm conditions. At harvest, the survival rate, harvest weight, food conversion ratio and yield of GMT was superior to those of MST and SRT (Mair et al . 1997). The YY male technology was then cascaded into different accredited local hatcheries and state universities for livelihood development and research. Most of these hatcheries were able to produce a good yield of tilapia; however, some resulted in an undesirable outcome due to contamination of their hatcheries (Mair et al . 1997). Farmed fishes may be genetically inferior compared to fish captured from the wild due to genetic erosion and farmmanagement issues (Ansah et al . 2014, Ordoñez et al . 2014). Inbred fish have become slow-growing and less fit (Romana-Eguia et al . 2019). To mitigate this predicament, fish strains have been genetically improved. Breeding and genetically modifying terrestrial and land animals can lead to increase in viability and agriculture productivity (Farias et al. 2017). The Philippines is a pioneer in genetic enhancement programs for tropical fishes. The initial focus in the generation of tilapia strains was on improving growth performance. In recent years, the production of tilapia strains that are tolerant to different culture conditions has been undertaken (Eknath et al . 1993, Eguia and Romana-Eguia 2016, Romana-Eguia et al . 2019). Some of the genetically improved tilapia strains are: • Genetically improved farmed tilapia (GIFT), • GenoMar supreme tilapia (GST), • Freshwater Aquaculture Center selected tilapia (FaST), • SaltUno tilapia strain, • Brackish water enhanced tilapia (BEST) and • Genetically enhanced tilapia-excellent strain (GET-EXCEL). GIFT Strain Tilapia from the GIFT project were the first produced for improved growth performance (Ordoneñez et al . 2014, Acosta and Gupta 2004). This genetic improvement project began in 1988 as a collaborative effort among public and private institutions, including the Freshwater Aquaculture Center of Central Luzon State University, ( C O N T I N U E D O N P A G E 6 2 ) Passive integrated transponder tags are used to identify broodstock used for selective breeding programs (Photo: J.A. Ragaza). A pond with groups of hapas (net cages) designated for the GET-EXCEL tilapia broodstock development program of the Bureau of Fisheries and Aquatic Resources National Freshwater Fisheries Technology Center (BFAR- NFFTC) in Muñoz City, Nueva Ecija, Philippines (Photo: J.A. Ragaza). The BFAR-NFFTC houses the Tilapia Germplasm Reference Collection Center for tilapia and other freshwater species from all over the world for broodstock development (Photo: J.A. Ragaza). Cryopreservation dewars for storage of frozen tilapia sperm in liquid nitrogen (Photo: by J.A. Ragaza).