International Journal of Aquaculture, 2025, Vol.15, No.3, 135-148 http://www.aquapublisher.com/index.php/ija 142 spring water to carry out factory-based tilapia breeding to overcome high-altitude low-temperature environments; the middle and lower reaches of the Yangtze River achieve overwintering attempts through greenhouse heating, and introduce tilapia into the local market. This expansion of the southern and northern diversion of fish is inseparable from the localization improvement of the product. To this end, China has bred a number of new tilapia varieties to meet local needs. In addition to the large-scale application of the "Jifu" strain, "Longjiang No. 1", "Yuemin No. 1" and "Guiluo No. 1" have been successively bred: for example, "Guiluo No. 1" focuses on low-temperature resistance, improves cold resistance through hybridization and group selection, and can survive outdoors in northern Guangxi in winter; "Yuemin No. 1" aims to improve male rate and growth rate, and has become the dominant variety of large-scale all-male seedling production in South China. In the process of expanding the tilapia industry, China also attaches great importance to environmental management and by-product utilization. For example, in the Pearl River Delta region, the technology of circulating water aquaculture and pond tail water treatment is promoted, and high-level pond aquaculture and rice field wetlands are combined to reduce the discharge load of aquaculture wastewater. Some breeding companies adopt online water quality monitoring and intelligent feeding systems to improve breeding accuracy while reducing environmental pressure (Yuan et al., 2017). In addition, through the development of tilapia processing and comprehensive utilization, such as fish meat products export, fish skin leather and collagen extraction, the added value of the industrial chain has been increased and the industrial sustainability has been promoted. 6.2 Egypt: high-density aquaculture and water resource reuse strategies Egypt is the most prominent country in Africa with tilapia farming, and its industrial characteristics can be summarized as high-density intensiveness and water resource recycling. The Nile Delta region of Egypt has a flat terrain and abundant water sources, making it very suitable for tilapia pond breeding. After decades of development, Egypt has become the world's second largest tilapia producer after China, with an annual output of more than 500 000 tons. In Egypt, tilapia are usually mixed with catfish in ponds, with stocking density up to thousands of tails per acre in order to pursue maximum output (Shaalan et al., 2018). This high-density farming benefits from Egypt's good water temperature conditions (the annual water temperature is mostly above 20 ℃) and sufficient feed investment. In addition, Egypt has adopted a unique water resource recycling model: many tilapia farms take water from the Nile irrigation canals, and the pond water is not directly disposal after fish farming, but flows into farmland to irrigate crops, achieving multi-use use of one water. Studies have evaluated the environmental sustainability of Egypt's family-style tilapia farms and found that through irrigation reuse, the impact of nutrient emissions from tilapia production on the surrounding environment has been significantly reduced. The Egyptian government also encourages this "fish-agricultural combination" model to ensure efficient use of water resources and pollution reduction while promoting tilapia farming. For example, pilot projects carried out in the Fayum area show that the use of aquaculture wastewater for growing aquatic vegetables can effectively absorb nitrogen and phosphorus from the breeding tail water, purify water quality and increase farmers' income. In terms of breeding technology, Egypt has also actively adopted modern means to improve the benefits of high-density breeding. For example, large-scale cage farming was deployed in the Nile tributaries, and the cage production in 2019 reached 119 000 tons, accounting for more than 10% of the national tilapia production. Cage farming makes full use of the fluidity of open water to reduce the dissolved oxygen pressure at high density of ponds (Radwan, 2020). At the same time, Egypt has effectively solved the problem of germplasm degradation caused by retail investors' self-propagation by establishing a centralized hatchery. 6.3 Brazil: conservation of genetic diversity and ecological integration breeding As the fastest growing country in Latin America, Brazil has expanded its industrial concepts that focus on the conservation of genetic diversity and ecological integration. Brazil began introducing tilapia in the 1990s. With its abundant water resources (large large reservoirs) and warm climate, tilapia farming output has doubled several times in the past decade, exceeding 500 000 tons in 2022, making it the second largest farmed fish after Kalu (Barroso et al., 2019). In terms of strain, Brazil attaches great importance to the genetic management of introduction. Early introductions include the Chitralada series in Thailand and the GST series in the Philippines. In order to avoid inbreeding and line degeneration, Brazil has established a national-level breeding center to preserve
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