Influence of the rearing system on phagocytic indexes and weight gain of the silver catfish (Rhamdia quelen, Quoy & Gaimard, 1824)

Abstract

Fish consumption has been growing since 1961. Indeed, the fisheries sector is essential to prevent hunger and malnutrition. However, this sector has its challenges. Fish stocks are being depleted beyond biological sustainability, with diseases and biosecurity risks to production and harm to the environment and ecosystems. There is a clear need to improve fish farming with minimum occupation and environmental impact. Heterotrophic and aquaponics systems are being utilized and modified to address these needs. However, environmental factors can affect the innate immunity of fish raised in these systems. Understanding how these systems affect fish’s immunity is critical to prevent potential hazards and the breakdown of these production methods. The goal of this research was to evaluate the performance, growth, and phagocytic indexes of silver catfish (Rhamdia quelen) juveniles reared in water recirculation, biofloc, and aquaponics systems in consortium with watercress seedlings (Nasturtium officinale). In each system, 12 juveniles weighing 15.2 g±7,6 were randomly divided into three replicates, fed with commercial feed. The following physical-chemical parameters - temperature, total and toxic ammonia, nitrite, and water pH - were daily assessed. Fishes were weighed monthly for six months. It was observed that R. quelen juveniles reared in the aquaponic system achieved higher average weight, but no statistical significance was detected (p>0.05) when compared to those reared in the recirculated and biofloc systems. At the end of the experiment, the phagocytic index was lower only in the recirculating system. The phagocytic capacity was lower in all systems. Although the aquaponic system presented low average weight gain/animal the performance of this system was effective in reducing the concentrations of total ammonia and nitrite in the water, in consortium with the production of vegetables.

Keywords

• phagocytic indexes
• aquaponic
• heterotrophic
• watercress
• rhamdia quelen
• índices fagocíticos
• acuaponia
• biofloc
• berro