72 DECEMBER • WORLD AQUACULTURE • WWW.WAS.ORG organic loading in water bodies, further depleting oxygen (NyinaWamwiza et al. 2010). There are some low-cost technologies which can help alleviate these challenges. Solar-powered paddlewheel aerators, venturi systems, and gravity-fed aeration devices can remarkably improve oxygen levels. Simple water testing kits can be used to regularly monitor DO, pH, and ammonia, providing farmers with the information needed for them to take preventative action before a crisis occurs. From Diagnosis to Slaughter: Gaps in Health and Humane Treatment The disease burden in African aquaculture is varied and significantly understudied, resulting in considerable knowledge gaps regarding effective prevention and control. Bacterial pathogens are widespread, with Aeromonas hydrophila and Streptococcus spp. causing devastating haemorrhagic septicaemia and systemic infections in tilapia and catfish across East and West Africa (Walakira et al. 2014; Ferguson et al. 2014; Kembenya et al. 2021) (Figure 4). Viral diseases pose a particularly severe threat; Tilapia Lake Virus (TiLV) has caused massive mortality events in Egypt, Ghana, Tanzania, and Uganda (Ferguson et al. 2014; OIE 2023). Furthermore, a multitude of parasites—including the protozoan Ichthyophthirius multifiliis (Ich) (Walakira et al. 2014; El-Sayed 2020), various monogenean flukes like Cichlidogyrus spp. (Pariselle et al. 2011), and crustacean parasites like Lernaea spp. (anchor worm) (Fuglem and Brito 2020) cause chronic stress and secondary infections, especially in overcrowded systems. The capacity to diagnose fish diseases remains critically underdeveloped across much of Africa. Without access to local laboratories equipped for pathology or molecular diagnostics, farmers often struggle to identify the correct pathogen, leading to inappropriate treatments and significant welfare and economic losses (Walakira et al. 2014). This diagnostic vacuum fosters the misuse of antibiotics. This practice is a primary driver of antimicrobial resistance (AMR), a global “One Health” crisis that compromises the treatment of bacterial diseases in both fish and humans (Romero et al. 2012). The lack of accessible vaccines for major regional pathogens further forces a reliance on reactive, rather than proactive, health management actions. The handling and killing of fish are also obvious welfare issues in Africa. Many small-scale farms use procedures that cause a great deal of stress and suffering, like manual netting, extended air exposure during sorting and transportation, and slaughter by ice immersion or air asphyxiation. Critically, methods like asphyxiation in air or immersion in ice water without prior stunning do not cause immediate unconsciousness. Fish can remain conscious and experience distress for many minutes as they slowly suffocate or go into thermal shock. The physiological response to such handling is profound, flooding the body with cortisol and adrenaline, which in turn depletes energy stores and suppresses the immune system, making fish susceptible to secondary infections (Barton 2002). From a product quality perspective, this stress leads to a rapid drop in muscle pH, resulting in softer flesh and shorter shelf life (Poli et al. 2005). Fortunately, more humane and practical alternatives are gaining traction. Percussive stunning involves a quick, forceful blow to the head, instantly rendering the fish unconscious. It is inexpensive, requires minimal equipment, and is highly effective. Percussive stunning significantly improves fish quality by preventing the buildup of stress hormones that can cause muscle stiffness, discoloration, and poor texture. The immediate loss of consciousness reduces bruising and blood spots, resulting in clean, appealing fillets with longer freshness and shelf-life. From a welfare standpoint, this method ensures the fish becomes instantly insensible to pain, lowering stress and physical struggle. Electrical stunning, passing a controlled electrical current through water stuns, all fish at once and is ideal for large operations. This method improves fish quality by rendering them unconscious simultaneously, which reduces stress and maintains uniform flesh characteristics. Keeping fish in water minimizes handling and damage, helping preserve their firmness and flavour. It provides immediate and painless loss of consciousness, prevents panic, and lowers suffocation stress, making it effective and humane for large-scale operations while adhering to international ethical standards. Using approved anaesthetic substances before slaughter ensures the fish feel no pain. The technique enhances fish quality by keeping them calm and stress-free before death, preventing the accumulation of lactic acid that can affect taste, texture, and appearance of meat. Gentle sedation ensures that muscles remain relaxed, which minimizes gaping and maintains aesthetic appeal and freshness. From a welfare standpoint, it offers a painless and tranquil process FIGURE 4. Catfish, such as this one grown in Uganda, face a number of bacterial pathogens across Africa. Photo courtesy SARNISSA. FIGURE 5. The path toward improved welfare requires collaboration across the entire African aquaculture value chain. Photo courtesy SARNISSA. No mention of Fig. 5??
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