Comparative study of the occurrence and distribution of parasites in pond and cage-cultured Nile tilapia (Oreochromis niloticus) in the Lake Victoria Crescent, Uganda

Abstract

Despite ongoing biosecurity and control efforts, aquaculture intensification in the Lake Victoria Crescent has led to a persistent increase in parasitic disease occurrence in cultured Nile tilapia. Notably, different culture systems provide different habitats and environmental conditions for parasites and understanding these dynamics may provide better management strategies. We compared parasitic infection/infestation rates of cultured Nile tilapia in pond-based and cage-based farming systems and identified associations between parasite dynamics and management in the Crescent. Trichodina spp. (most prevalent and abundant) and Cichlidogyrus spp. were found in all systems. Pond systems contained ≥11 parasitic genera while ≤5 were found in cage systems. Parasite dynamics were modelled using generalised linear models with zero-inflated Poisson or zero-inflated negative binomial distributions. Surprisingly, in pond systems, adequate stocking densities and feeding were associated with an increase in Cichlidogyrus spp. abundance, while sourcing seed from fellow fish farmers was associated with a decrease in Trichodina spp abundance. For cage systems, adequate stocking densities and feeding were associated with an increase in Trichodina spp. abundance. Wild fish entry was associated with an increase in Cichlidogyrus spp. abundance while optimal stocking density was associated with a decrease in Cichlidogyrus spp. abundance. These findings highlight the interactions between seasonality and farm management in the control of parasites.