Simple Summary: This study examined the abundance of zooplankton groups (copepods and ostracods) and their correlation with acanthocephalan parasites in fish farms across Rondônia's Vale do Jamari and Centro-Leste regions during rainy and dry seasons. Conducted in 41 fish farms from November 2021 to September 2023, it included water, zooplankton, and fish samples from 196 Colossoma macropomum. Results revealed that 95% of farms had fish infected with Neoechinorhynchus buttnerae, with higher parasite densities in municipalities like Ariquemes and Ji-Paraná. Water quality was suitable for fish farming. Zooplankton presence, particularly copepods and ostracods, correlated with parasitic infestations, suggesting their potential as ecological indicators. Monitoring these communities is critical for detecting changes in artificial ecosystems, such as fish farms, to mitigate long-term effects. This study investigated the abundance of zooplankton copepods and ostracods taxonomic groups in fish farms in Rondônia's Vale do Jamari and Centro-Leste microregions during the rainy and dry seasons. It also analyzed the correlation between zooplanktons abundance and the presence of acanthocephalan parasites. Conducted in 41 fish farms between November 2021 and September 2023, the study included water, zooplankton, and fish samples from 196 Colossoma macropomum. The results showed that 95% of the farms had fish infected with Neoechinorhynchus buttnerae, with varying parasitism levels. Georeferencing revealed higher parasite densities in the municipalities of Ariquemes, Monte Negro, Machadinho do Oeste, and Buritis (Vale do Jamari), as well as Urupá, Ji-Paraná, Ouro Preto do Oeste, and Teixeirópolis (Centro-Leste), with clusters of heat islands in the latter group. Water quality parameters were suitable for raising C. macropomum. The presence of ostracods and copepods could serve as indicators of parasitic infestations, highlighting the importance of monitoring zooplankton and parasite communities. This approach is valuable for detecting changes in artificial ecosystems, such as fish farms, which could lead to significant long-term effects. [ABSTRACT FROM AUTHOR]

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