Growth comparison of three strains of red tilapia (Oreochromis spp.) in two stocking densities under intensive culture conditions

Aquaculture is a growing industry in the country and it continues to supply the rising demand for fish for the increasing population. Intensive aquaculture has started to flourish in the country and it involves the culture of freshwater fish species such as tilapia and catfish in drums and tanks of concrete, fiberglass or canvas in highly urbanized areas. Tilapia ranked third among the major species produced in aquaculture fisheries. It is considered the aquatic chicken due to its various desirable characteristics like being hardy, it can survive and tolerate stress and poor water quality, it accommodates wide salinities and adapts to a variety of rearing and culture conditions. Among the issues that need to be addressed in intensive culture systems are strain and stocking density. The study is an effort for the identification of candidate strain for rearing in intensive systems based on a comparison of growth and survival rates and the determination of ideal stocking density to maximize production. Three commercial strains of Red tilapia (Oreochromis spp.) (FAC or Freshwater Aquaculture Center of CLSU, Nueva Ecija, Singaporean strain maintained in a private farm from Calatagan, Batangas and Thailand strain maintained in a private farm in Calaca, Batangas) were reared in plastic 60-L tanks (triplicates) in two stocking densities (Low 20 test fish: 20 reference fish, High 40 test fish: 40 reference fish) for 112 days. Nile tilapia (Oreochromis niloticus) was used as the internal control for the study. The fish were fed commercial feeds (starter 1 pellet super premium floating feeds from BMEG Corporation) containing 40% crude protein twice (9:00am and 4:00pm) daily ad libitum. The feeds were given at the following rates: 5%, 5%, 3% of the total biomass in each tank, respectively for three months with the feed rations being adjusted biweekly. Water quality parameters including temperature, dissolved oxygen, pH, ammonia, nitrite and nitrate concentrations were monitored throughout the duration of the study. Specific growth rate (P = 0.013) and survival rate (P = 0.000) differed significantly among the strains where FAC grew best at 0.87%/day and survival rate of 85.83%. FAC red tilapia can be considered as the candidate strain for intensive culture conditions. There was no significant difference in specific growth rate (P = 0.305) and survival rate (P = 0.863) of red tilapia fingerlings in low and high stocking densities. Low stocking density is preferred to produce larger individual fish. If the farmer desires to produce higher yield but small individual fish, high stocking density is recommended. Red tilapia fingerlings from Calaca and Calatagan or any other available stocks can still be used for culture in the absence of FAC strain for as long as the farmer manages them properly