Mutilation on gill filaments of Piaractus brachypomus (Characiformes: Serrasalmidae) caused by Braga patagonica (Crustacea: Cymothoidae), in the Brazilian Amazon.

Fish aquaculture is one of the main food production sectors for the growing global human population and is currently one of the most profitable production activities. However, parasitic infestations have emerged as a significant factor influencing fish aquaculture production, negatively impacting the profitability of this food production activity. This study aimed to report the mutilation of pirapitinga Piaractus brachypomus gill filaments caused by a Cymothoidae parasite. In April 2022, Piaractus brachypomus were examined at a fish farm in Macapá, state of Amapá, Brazil. The host fish were analyzed, and the parasite found was preserved in 70% ethyl alcohol for taxonomic identification. Of the 31 fish examined, one had its gills infested with a crustacean parasite identified as Braga patagonica. A female parasite caused macroscopic mutilation of the filaments on the four right gill arches of P. brachypomus and severe damage at the attachment site. This is the first record of B. patagonica infestation in P. brachypomus. The fish farming water supply allowed the isopod ectoparasite to pass from wild fish to the pond, where it consequently found favorable conditions in the host fish.