In the present study, some limnological factors of earthponds of monosex and mixed tilapia culture were investigated during the breeding season of 2016. Comparison of the length and weight of the cultured tilapia and FCR between two treatments in the earthponds indicate a more favorable growth performance in monosex tilapias, as expected.
Tilapias are the world’s second largest farmed fish and their production in the world has sharply increased, especially in recent decades. Nile tilapia, Oreochromis niloticus production consisted more than 70% of total farmed tilapia in the last decade. Tilapia farming is now done in more than 135 countries and its’ global production has exeed than 5.6 million tons (Fitzsimmons, 2016; FAO, 2014).
Nile tilapia O. niloticus samples were entered to Iran for research purposes at December 2008 for the first time. Studies about the feasibility of introduction of tilapia to inland aquaculture in Iran were begun in National Research Center of Saline Water Aquatics in Yazd province at the center of Iran (Rajabipour, 2013). Different aspects of reproduction, culture, feeding, monosex production, processing are studied (Bitaraf, 2012; Mashaii et al., 2016; Mohammadi et al., 2014; Morady et al., 2012; Rajabipour, 2013 & 2016; Sarsangi et al., 2012).
In the present study, some limnological factors of earthponds of monosex and mixed tilapia culture were investigated during the breeding season of 2016. The minimum and maximum of water temperature ranges were 16.6-27.5°C and 20.5-31°C, air temperature 2-27°C and 30-48°C, dissolved oxygen in the morning and afternoon 2.11-10.19mg/l and 7.06-14.64mg/l, pH in the morning and afternoon 8.97-10.9 and 9.04-13, the depth of transparency 40-105cm, salinity 7.94-8.82ppt and ammonium density less than 0.05mg/l to 0.4mg/l. The most abundant phytoplankton and zooplankton were Chlorophytes, diatoms and rotifers, and dominant macrobenthos were chironomids. There was significant positive correlation between pH value with ammonium density and body length and weight, water temperature with total length, and negative correlation between dissolved oxygen and temperature and pH (p<0.05). Tilapia culture in earthponds has advantages especially for using water biomass by fish and lower costs of the structures. Comparison of the length and weight of the cultured tilapia and FCR between two treatments in the earthponds indicate a more favorable growth performance in monosex tilapias, as expected.