Bacterial community in African catfish (Clarias gariepinus) recirculating aquaculture systems under different stocking densities

Abstract

Fish farming in Recirculating Aquaculture Systems (RAS) is a sustainable and efficient practice to produce fish. Knowledge of microbial communities, particularly harmful pathogens on fish, is required to better understand microbiological processes occurring at different RAS compartments and to optimize the overall RAS management. In this study, we assessed the influence of different Clarias gariepinus stocking densities in RAS on the water microbiome composition. Molecular targeting the V3-V4 16S rRNA hypervariable region was used to infer Amplicon Sequence Variants (ASV), identify microbes, and assess their abundance and diversity. We identified bacterial pathogens in the rearing environment associated with common fish farming practices. Our findings show that microbiomes differ across all systems (high, medium and low stocking densities) and within sampling points (water inflow, outflow and sedimentation tank). The medium-density system had the most fish biomass, resulting in high ASVs cumulative abundance. In water samples from high- and low-density systems, we discovered a wide range of phyla, with Mycobacterium sp. being the most common potentially pathogenic group. We discuss the effects of fish biomass and water physicochemical properties on the microbiome.

Aquaponics nomenclature matters: It is about principles and technologies and not as much about coupling

“…Likewise, the bacterial community of the RAS process water changes with stocking density. 48 This will make process modelling of single nutrient fluxes under real commercial conditions truly challenging. Consequently, any threshold must apply to the total plant growth independent of the deficient nutrients and/or their proportions that are responsible for the reduced growth compared with the possible optimum under regular farming conditions.…”

“…The resulting process waters arriving at the plant units changed drastically, preventing a constant and foreseeable macro‐nutrient composition. Likewise, the bacterial community of the RAS process water changes with stocking density 48 . This will make process modelling of single nutrient fluxes under real commercial conditions truly challenging.…”

Haplotype-resolved assembly of the African catfish (Clarias gariepinus) provides insights for semi-terrestrial adaptation of airbreathing catfishes

“…This omnivorous fish is quite resilient due to its ability to cope with extreme environmental conditions, tolerate various land-based farming practices and a large diets spectrum 8 – 11 . In addition to its rapid growth, extreme robustness 11,12 , and relatively high fecundity, C. gariepinus can withstand high levels of ultraviolet B (UV-B) radiation and dramatic temperature fluctuations in non-aquatic environments 13,14 . This ecological flexibility could explain its hardiness and wide geographical distribution.…”

“…garipinus is found primarily throughout Africa, where it was first introduced in aquaculture around mid 1970s. This omnivorous fish is quite resilient due to its ability to cope with extreme environmental conditions, tolerate various land-based farming practices and a large diets spectrum [8][9][10][11] . In addition to its rapid growth, extreme robustness 11,12 , and relatively high fecundity, C. gariepinus can withstand high levels of ultraviolet B (UV-B) radiation and dramatic temperature fluctuations in non-aquatic environments 13,14 .…”

“…This omnivorous fish is quite resilient due to its ability to cope with extreme environmental conditions, tolerate various land-based farming practices and a large diets spectrum [8][9][10][11] . In addition to its rapid growth, extreme robustness 11,12 , and relatively high fecundity, C. gariepinus can withstand high levels of ultraviolet B (UV-B) radiation and dramatic temperature fluctuations in non-aquatic environments 13,14 . This ecological flexibility could explain its hardiness and wide geographical distribution.Interspecies hybridization with closely related clariids has been shown to improve C. gariepinus environmental tolerance, manipulate sex ratios, and eventually increase growth performance, making it a highly efficient aquaculture fish 15 .…”