2.3 Stock management and feeding practices
Two of the main areas for technology development that have driven much of the expansion of aquaculture around the world are firstly the closing of the production cycle. This has been achieved though management and spawning of broodstock, the collection and hatching of eggs, and the rearing and weaning of offpring. Each of these stages require separate consideration of welfare needs. Furthermore, the use of hatcheries has enabled selective breeding programmes which are altering the characteristics of the farmed animals. The second area for development has been in the field of nutrition, and particularly the formulation of suitable compounded diets for many species. These potentially resolve some welfare issues, but also raise new ones.
Breeding and genetics:
Reproductive practices (broodstock selection, environmental parameters during hatching, larvae feeding, and handling during reproduction), and the consequent genetic outcomes from these practices, are crucial determining factors towards fish welfare. Selective breeding can result in both positive effects (e.g., producing less aggressive / more docile / disease-resistant offspring) and negative effects (e.g., malformations of the spine / jaw that can impact feeding, mobility, or respiration). Improper use of anaesthetics and handling of broodstock can also pose serious risks to welfare (and survival) at a time when the animal is already under significant duress. An example of improper breeding practices that can severely impair welfare is eyestalk ablation in shrimp; this method of inducing maturation and spawning can cause negative impact on shrimp such as pain and stress, physiological imbalance, reproductive exhaustion, activation/reduction of immune related genes, high broodstock mortality and compromise offspring quality (e.g. decrease robustness to environmental stress and typical diseases). It is, therefore, a priority to adopt alternative techniques for improving farmed shrimp welfare. Alternatives can include a mix of approaches of approaches such as improving some key hatchery and breeding practices (e.g. male and female sex ratio, use of high quality broodstock feeds, selective breeding), sourcing appropriate genetic strains, staff training and other welfare improvements etc. In the following video, Dr Simao Zacarias describes his research and findings in this area.
NB: This third-party video is linked for illustration only and copyright and control belong entirely to the originating organisation
For additional explanation please see the following video.
NB: This third-party video is linked for illustration only and copyright and control belong entirely to the originating organisation
Feeding practices and nutrition:
The intake of food with sufficient nutritional content is a fundamental need for growth, physiological functioning / immune-competence, and health. Outside of the ‘ultimate’ need for proper feeding practices, insufficient / poor quality feed will lead to stressed and less resilient animals, and potentially more intra-species aggression with certain individuals being outcompeted for food. Various aquatic animals have also exhibited strong anticipatory behaviours for their preferred food sources, indicating an emotional qualitative component of wanting and liking. An essential aspect of satisfying welfare needs therefore includes feeding animals to their species and life-stage specific rations. Conversely, since most aquatic animals are ectotherms, short periods of food deprivation may be of less detriment in comparison to endotherms. Water treatment systems in place must match the intensity of feeding involved; for example, supplemental feeding of natural grazing in unfertilised ponds require less maintenance whereas closed, intensive systems on full feed must be cleaned routinely with a flow of fresh water.