By Dr Mustapha ABA. Scientific Expert in Aquaculture. Fish Nutrition. Rabat. Morocco
The welfare of fish and other aquatic organisms is not only a question of ethics, it is also a crucial factor in the quality and safety of aquatic products. Stressed or poorly cared for aquatic animals are more susceptible to disease, which can lead to significant economic losses and risks to public health. In addition, the quality of aquaculture products is strongly influenced by animal welfare. Fish and other aquatic organisms reared under ideal welfare conditions tend to have better quality meat, with superior texture, flavour and nutritional value. This meets consumer expectations for healthier, higher-quality products, which increases competitiveness in the marketplace. However, the effective management and welfare of aquatic organisms are fundamental to ensuring the sustainability and productivity of this sector.
In Africa, concern for the welfare of fish during production processes is at an early stage. The main objective of this article is to highlight the importance of fish feeding in terms of welfare in the development and implementation of sustainable aquaculture.
Introduction
The growing importance of fish welfare in aquaculture stems from ethical considerations as well as the prospect of improving standards and quality of fish production technologies and aquaculture products (Segner et al., 2019).
Aquaculture is not only a massive industrial activity that integrates human food with high quality food, but also contributes to the recovery of fish populations for commercial and conservation purposes (Brown and Day, 2002, Toni et al., 2019). Farmed fish must be maintained not only painlessly for ethical and practical reasons, but also in conditions similar to those of their wild counterparts to ensure the success of restocking schemes (Huntingford et al., 2006).
The welfare of fish in aquaculture can be assessed using the freedoms proposed by the UK Farm Animal Welfare Council (1992), which set out the five well-known animal freedoms:
(1) freedom from hunger or thirst ;
(2) freedom from discomfort;
(3) freedom from pain, injury or disease;
(4) freedom to express normal behaviour ;
and (5) freedom from fear or distress.
These requirements have led to changes in technical regulations and aquaculture standards, which now consider animal welfare to be a prerequisite for production (Branson, 2008; Medaas et al., 2021; Seibel et al., 2020). The World Organisation for Animal Health, formerly known as the OIE (Office International des Epizooties), has set standards for the welfare of aquatic animals, including farmed fish (OIE, 2021), but there is still no directive specifically targeting fish welfare (Giménez-Candela et al, 2020), and strategies to improve fish welfare have only recently begun, in the last two decades (Grimsrud et al., 2013, Keliber et al., 2023).
However, aquaculture farming practices also involve unpredictable events such as cleaning, transfers, sorting, oocyte collection, sudden lighting, weighing and vaccinations, which make farming conditions unpredictable and uncontrollable and therefore potentially stressful for fish (Colson et al., 2019; D’orbcastel et al., 2009; Karakatsouli et al., 2007).
Feed is one of the biggest production costs in an aquaculture farm and can be one of the main factors in fish welfare (López-Olmeda et al., 2012).
Welfare promotes the quality of life and survival of fish, which has become a subject of interest in the aquaculture sector since it began using indicators of good aquaculture practice. Due to its complex definition, a multitude of physiological and behavioural indicators or indices have been developed which, only when analysed together, provide information on the state of animal welfare (Tort et al., 2011; Dara et al., 2023). Some of the most commonly used indicators in fish are changes in colour (Kittilsen et al., 2009) or behaviour (Morton, 1990), reduced consumption (Upton & Riley, 2013), morphological abnormalities (Boglione et al., 2001) and lesions (Turnbull et al., 1998). Feeding control and water quality monitoring are fundamental to balancing fish productivity and shaping the fish growth process, reducing operating costs and fish losses and increasing the efficiency of growth production, resulting in fish welfare and health (Aljehani et al., 2023). Aquatic animals that are not chronically stressed have better growth rates, are less prone to disease and the end product retains high quality characteristics (Sneddon et al., 2016).
- Adequate nutrition and feeding are fundamental to maintaining fish health and welfare, improving performance and disease resistance and reducing sensitivity to environmental impacts (Alfaro et al., 2016; Martin and Król; 2017; Oliveira et al., 2024. Thus, with the increase in aquaculture production, studies on how nutrients and feed ingredients affect these parameters are becoming increasingly important, especially as the composition of ingredients and nutrients in new diets can be highly variable and, although they often do not impact growth, their effect on fish health, stress and disease susceptibility is receiving more and more attention (Oliveira et al., 2024). Appropriate dietary intake is important for good welfare, as poor diets can lead to high mortality and disease susceptibility or indicate the presence of disease (Barreto et al., 2021). In addition, food competition is a common challenge in fish management that can lead to agonistic behaviour between fish or restricted access to food for subordinate individuals. As a result, the monitoring of feeding behaviour is useful for welfare as well as production purposes in aquaculture (e.g. Montero et al., 2009; Okonomidou et al., 2019). However, feeding behaviour is complex and cannot be used as a welfare indicator on its own. In addition to welfare status and homeostatic control, feeding behaviour is also influenced by a range of environmental factors such as temperature, breeding season and the presence of predators. (Volkof and Peter, 2006). Consequently, feeding behaviour must be measured in conjunction with other indicators of well-being and should not be considered as a single indicator (Barreto et al., 2022).
- Appetite-led feeding may also be beneficial for welfare, as intensively cultured fish have little control over what they eat and when, despite known fluctuations in appetite with time of day and environmental conditions (Juell et al. 1993, Mallekh et al 1998, Macaulay et al., 2022).
- Feeding time: fish have distinct feeding rhythms, and feeding time influences the stress responses (physiological and behavioural) of fish, depending on the species-specific daily feeding behaviour. In addition, this time factor can have an interactive and additive effect on other welfare indicators, such as the effect of meal timing on aggression and the additional role that aggression plays in increasing injury and mortality (López-Olmeda et al., 2011).
- Poor distribution or excessive quantities of aquaculture feed, can lead to degradation of water quality (Boyd and Tucker, 2019).
- Feeding rate: Providing inadequate amounts of feed can lead to increased aggression in fish, causing injury and promoting the spread of disease (Liang and Chien, 2013; López-Olmeda et al., 2012; Pedrazzani et al., 2022). In aquaculture, if fish do not have sufficient access to food, this leads to slower growth and longer production times (Imsland and Methúsalemsson, 2024).
- Feeding frequency should be a priority as it affects both the growth and survival of fish, especially during their early life stages (Villarroel et al., 2011). Optimum feeding frequency results in the best growth rate for fish due to improved food consumption, linked to gastric evacuation, which increases fish appetite (Riche et al., 2014). On the other hand, a higher feeding frequency increases fish rearing costs and increases waste accumulation, which negatively affects water quality (decrease in dissolved oxygen and increase in ammonia content) (Tian et al., 2015, Ayisi et al., 2021).
Good management and the promotion of the well-being of aquatic organisms are fundamental pillars of sustainable aquaculture. Fish feed must be balanced and adapted to the specific needs of each species. Inadequate feed can lead to nutritional deficiencies, stunted growth and increased susceptibility to disease. Implementing effective management practices and innovative strategies to promote animal welfare not only improves fish health and productivity, but also contributes to environmental sustainability and food security. Awareness and continued commitment to these practices are essential for the future of aquaculture in Africa.
