Fish diversity in a human-impacted coastal lagoon in Central Peru (~10°78’ °S)

Eight fish species were recorded in a heavily impacted coastal lagoon on the central Peruvian coast. Despite anthropogenic pressures such as waste disposal and habitat fragmentation, the lagoon still supports a typical estuarine fish assemblage, reflecting the resilience of this ecosystem. A total of 2357 individuals representing eight species, seven families, and five orders were collected. The identified species were Bryconamericus peruanus, Dormitator latifrons, Lebiasina bimaculata, Poecilia reticulata, Ctenogobius sagittula, Mugil cephalus, Cichlasoma nigrofasciatum , and Aequidens rivulatus . Among these, B. peruanus and D. latifrons were dominant, comprising more than half of all captures. Most individuals were juveniles, confirming that the Totoral Lagoon functions as a nursery ground that provides favorable conditions for growth and recruitment, including abundant food, vegetation cover, and stable physicochemical parameters. Fish were concentrated in shallow, vegetated, muddy zones where freshwater and marine influences converge. These areas serve as refugia and feeding grounds, particularly for species that complete early life stages within the lagoon. Native taxa such as L. bimaculata, D. latifrons , and C. sagittula occurred in lower densities, mostly in low-salinity areas with fine sediments, indicating the persistence of localized freshwater microhabitats. Overall, the structure and composition of the ichthyofauna reveal a marked ecological gradient from freshwater to brackish zones, reinforcing the lagoon’s function as a key transitional ecosystem along the Peruvian coast.