28 JUNE 2023 • WORLD AQUACULTURE • WWW.WAS.ORG tilapia stocked in in-pond raceway systems (IPRS) at a commercial farm in Colombia. The objective was to identify the key aspects that allow the realization of greater profitability in Nile tilapia aquaculture. Materials and Methods Facilities This study was carried out in five earthen ponds located on a commercial tilapia farm in the Department of Huila, Colombia (Fig. 1). Two ponds of 1.90 and 3.12 ha were stocked at a density of 5.5 fish/m² (HD), two ponds of 1.83 and 2.55 ha were stocked at 3.9 fish/m² (LD) and one pond with IPRS technology (Fig. 2) of 1.15 ha were stocked at a rate equivalent to 13.3 fish/m² (Table 1). All fingerlings were obtained from tilapia nursery farms located in the area that are certified as biosecure establishments. The ponds with HD and LD treatments included mechanical aeration with vertical pump (splash-type) aerators at approximately 8 hp/ha. The pond with the IPRS consists of four fish production cells (raceway channels), four blower motors of 2 hp each and two paddlewheel aerators of 2 hp each (~10 hp/ha), all to oxygenate the water and generate water movement in a circuit around the pond. At the end of the production cells there is a quiescent zone for sedimentation of solids that are removed regularly by a pump. Feeding Fish were fed with a commercial feed with an initial protein level of 45 percent, which was gradually reduced to 38, 34, 32 and 30 percent according to the body weight of tilapia during the production cycle. The amount and type of feed was adjusted biweekly using a feeding rate table. For the first-stage phase, five daily rations of feed were supplied manually and for the second, grow-out phase, two rations per day were supplied with a tractor towing a feed hopper and a blower for feed distribution. Fish in the pond with the IPRS were fed manually, distributing the daily feed allotment in four rations. Average Introduction Global production of tilapia in 2020 was almost 7 million t. Currently, a wide variety of tilapia species are cultivated, but Nile tilapia is the most commercialized worldwide, ranking third among farmed finfish with 8.3 percent (FAO 2020). Tilapia farming has evolved and is currently carried out in earthen ponds, floating cages, concrete tanks and framed tanks with plastic liners. Tilapia were introduced to Colombia in the 1960s. The country experienced an increase in production in 2020, driven by the optimization of agricultural areas and improvements in technology and feeds, unlike what occurred in China, Indonesia and the Philippines, where the effects of the COVID-19 pandemic had a negative impact. Latin America and the Caribbean play an important role in the world production of aquatic animals, with growth prospects of 33 percent in the next ten years (Souto Cavalli et al. 2021). Stocking density is an important parameter in tilapia aquaculture as it has a direct effect on growth, mortality and production (Sharmin Aktar et al. 2016). High loading rates affect fish growth, health and survival (Procarione et al. 1999). The increase in stocking density, in addition to causing a negative effect on growth, strongly influences the dispersion of sizes, suppressing the growth of some individuals (Irwin et al. 1999, Schram et al. 2006). Crowding and/or competition for feed also can be the main causes of size variation (Yousif 2002). Fish at high densities are exposed to chronic stress, which in turn results in decreased feed intake, growth and survival. Therefore, a greater number of cultured animals does not always represent greater harvested biomass. Production technology and the requirements of each species must be taken into account. The objective of any fish farm is to produce the maximum biomass in the most efficient way possible. This article describes a study that evaluated the effect of stocking density on tilapia production. Production performance of tilapia in traditional earthen ponds stocked at high and low densities was compared with that of Production of Nile Tilapia in Traditional Ponds Stocked at High and Low Density Compared to IPRS Esau Arana, Mildred Avila, Oscar Botero and Jesse Chappell FIGURE 1. Botero tilapia farm in Huila, Colombia. FIGURE 2. IPRS made of low-cost materials at Botero tilapia farm.