Piaractus brachypomus constitutes a significant component of Peruvian Amazonian aquaculture, with an annual production of 3,104 MT (Produce, 2023). This study aims to document and analyze an episode of acute mortality in P. brachypomus fingerlings cultured in a semi-intensive system, identify the etiological agents involved, and quantify the resulting economic impact.
A sample of 30 specimens was selected from a batch of 4,500 fingerlings, with an average body mass of 8.50 g and an average standard length of 6.71 cm. Clinical, parasitological (through skin and gill scrapings), microbiological (bacterial cultures), mycological (lactophenol blue staining), and histopathological (H&E staining) evaluations were performed. Daily mortality was monitored, and economic impact was quantified.
Parasitological analysis revealed a 100% prevalence of Ichthyophthirius multifiliis, with a mean intensity of 63 parasites per host. Additionally, 23.3% of the specimens presented a secondary fungal infection by Saprolegnia sp. Microbiological analyses indicated that 100% of the individuals exhibited concomitant infections by opportunistic bacteria, mainly Plesiomonas shigelloides and Aeromonas spp. Histopathological examination of the gills showed significant alterations, including congestion of the central vein (90%), detachment of the secondary lamellar epithelium (90%), and fusion of secondary lamellae (70%).
Mortality progression was rapid, reaching 20% at 10 days post-stocking and culminating in total mortality (100%) at 15 days. The economic impact was quantified at $1,986.54 USD over the 10-day culture period, of which 95.02% corresponded to non-recoverable production costs.
It is concluded that the high prevalence and intensity of I. multifiliis, along with secondary fungal and bacterial infections, were the main factors leading to mass mortality, likely exacerbated by transport stress and adaptation to the new environment. This case underscores the critical importance of implementing rigorous health management protocols in Amazonian species aquaculture.
The establishment of a minimum 15-day quarantine period for new batches is recommended, accompanied by a gradual acclimatization process and daily monitoring of stress indicators and ectoparasite presence. The application of these preventive measures could significantly reduce the susceptibility of fingerlings to infections and mitigate the consequent economic losses, contributing to the sustainability of the Amazonian aquaculture industry.