Tilapia studies in Iran were begun since 2008. Now, various rearing systems are used for semi-intensive and intensive tilapia culture. In the present study, limnologic factors of indoor and outdoor tilapia culture ponds, also growth performance of the cultured tilapia were investigated. Both systems have advantages and disadvantages.
Growth performance and limnologic factors of indoor and outdoor tilapia culture ponds were investigated. In the earth ponds, the ranges of minimum and maximum of water temperature were 16.6-27.5°C and 20.5-31°C, dissolved oxygen was 2.11-10.19mg/l in the morning and 7.06-14.64mg/l in the afternoon. PH was recorded 8.97-10.9 in the morning and 9.04-11.00 in the afternoon. The depth of the water transparency was 40-105 cm. Water salinity was 7.94-8.82 ppt. The concentration of NH4+ was less than 0.05 to 0.4 mg/l. The frequency of phytoplankton and zooplankton was 2050-2848 and 269-101 per liter, respectively, macrobenthos was 3467-558/m2. The dominant phytoplankton, zooplankton and macrobenthos were chlorophytes and diatoms, rotifers and chironomids, respectively. Pearson 2-tailed correlation between the amounts of temperature, salinity, dissolved oxygen, pH, NH4+, length and weight of farmed fish in earth ponds showed a direct significant correlation between pH value against ammonium concentration, and total length against body weight of the fish, also between pH against water temperature and total length of the fish.
In indoor tanks, the range of water temperature was 29-24°C, dissolved oxygen 1.65-8.38mg/l, pH 9.37-7.25, water salinity 7.12-7.7ppt, and ammonium 0.16-0.5 mg/l.
Pearson 2-tailed correlation between the amounts of temperature, salinity, dissolved oxygen, pH and ammonium with length and weight of fish showed a direct significant correlation between the length and weight of the fish body with each other, the amount of salinity against pH, salinity against total length and body weight. Also, there was a reversed significant correlation between the amount of dissolved oxygen against water temperature, pH and the total length of fish.
Both in earthen pools and indoor ponds, there has been a significant increase in the average size of the length and weight of the reared fish in the last months of the breeding period, that is expected.
Raising tilapia in earthen ponds is a common method of raising this fish because the cost of infrastructure is relatively low. Also, it is possible to provide the nutrients based on fertilization, leading to reducing the cost of fish production. However, it should be noted that high temperature and wind cause water evaporation, which is not recommended, especially in dry areas.
In indoor ponds, as well as other closed systems such as greenhouses and aquaponics, it is possible to breed tilapia twice a year, in addition to conserving water and higher densities fish production, while they are more compatible with environmental considerations.