70 DECEMBER • WORLD AQUACULTURE • WWW.WAS.ORG This article explores the complex connections between common aquaculture practices and fish welfare across Africa. Here, we highlight practical, actionable solutions that can protect animal wellbeing, promote the sector’s sustainability, and maintain its economic viability. The Squeeze: How Overcrowding Stunts Growth and Spreads Disease In the pursuit of higher yields, overcrowding has become a widespread problem in African aquaculture. Stocking density is a key factor in fish welfare, with financial pressures often leading farmers to stock ponds, tanks, and cages with too many fish, causing a chain of negative effects. The science behind this is clear. High stocking densities activate the fish’s primary stress response system, leading to a sustained release of cortisol into the bloodstream (Barton 2002). While this hormone is useful for short-term survival, its chronic elevation is devastating: it suppresses the immune system, making fish easy targets for bacteria and parasites (Figure 1), and redirects energy away from growth and reproduction (Odhiambo et al. 2020). Research on African catfish suggests that optimal densities should be around 7 fish/m²; beyond this, farmers see reduced growth rates, increased aggression leading to fin damage, and higher mortality (Ojonugwa and Solomon 2017; van de Nieuwegiessen 2009). Juvenile catfish are especially vulnerable, showing reduced feeding efficiency and heightened stress responses when crowded (van de Nieuwegiessen et al. 2008). Nile tilapia, a species with complex social hierarchies, also suffers profoundly from overcrowding. Overcrowding disrupts their natural behaviour, leading to increased aggression, suppressed reproductive performance, and chronic stress (Rodriguez-Barreto et al. 2019; Sapkota et al. 2022). Overstocking often leads to a suite of additional challenges. Waste accumulation, which degrades water quality, can further stress the fish and make the negative effects of density even worse. The solution requires a shift in mindset from maximum stocking to optimal stocking. Key management strategies include implementing species-specific density guidelines, training farmers to recognize behavioural signs of stress, and adjusting stocking levels seasonally to account for temperature and water quality fluctuations. African aquaculture is a powerhouse of potential. Contributing approximately USD 24 billion to the continent’s economy, it also serves as a vital solution to food security challenges (Akegbejo-Samsons, 2022; de Graaf and Garibaldi, 2014). The sector is highly diverse, ranging from extensive rural ponds that rely on natural productivity to intensive, capital-intensive systems in commercial set-ups. Each of these production types presents its own unique welfare challenges influenced by management practices, environmental factors, and available resources (Amponsah et al., 2025). However, as the sector progresses from traditional methods to more intensive production, it encounters a complex obstacle: ensuring the health and welfare of the fish themselves. This intensification, driven by rising demand for protein, has exposed critical gaps in how we manage fish wellbeing. Highdensity systems, while productive, can become hotbeds for stress and disease, creating ideal conditions for pathogens to thrive (van de Vis et al. 2020). These challenges are especially pronounced in Africa’s tropical climates, where warm temperatures accelerate pathogen development and metabolic processes. The industry’s dependence on a limited number of key species, mainly the resilient Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus), results in vulnerability, as diseases can spread quickly through monocultures. Compounding this are inconsistent farming practices, variable knowledge levels, and a critical shortage of veterinary and diagnostic services (Opiyo et al. 2018; Brummett et al. 2008). In light of these challenges, understanding the intersections between cultural practices and fish health outcomes becomes essential for developing sustainable management strategies that balance productivity with animal welfare. This goes beyond simple survival; it encompasses the physical and psychological well-being of fish under human care. Scientists and progressive farmers evaluate animal welfare using various practical indicators, typically structured around five key areas: nutrition, environment, health, behaviour, and emotional state. These indicators range from simple observations of fish behaviour and physical condition to more specific production metrics, such as growth rates and survival statistics. By analysing these factors, farmers gain valuable insights into the farming process and the animals’ condition. This information enables them to make informed management decisions, transforming abstract concepts of welfare into tangible practices on the farm. A Review of Fish Health and Welfare Challenges in African Aquaculture: Implications of Cultural Practices Tafadzwa Maredza and Alice Namata FIGURE 1. High stocking densities can activate stress responses that suppress the immune response. Photo courtesy SARNISSA.
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