Aplicação de drones subaquáticos no monitoramento ambiental em águas interiores: acessando a distribuição vertical dos peixes e a seletividade do método

Abstract

A new approach for visual fish survey in reservoirs using underwater drones (remotely operated vehicle- ROV) is presented. The ROV was applied to identify abiotic gradients and to compare fish assemblages on the steep slopes in a tropical reservoir. The tested hypothesis is that fish are concentrated in the littoral zone due to the better physicochemical and habitat conditions, compared to deep and hypoxic layers. Twelve species were recorded (seven native, five non-native, with all species occurring in the littoral zone (1-7 meters deep), seven species in the transition (7-15 m), and four in the profundal zone (> 15 m). A greater fish abundance and richness was found in the littoral zone corroborating the hypothesis. The littoral zone was dominated by non-native cichlids (Cichla spp., Coptodon rendalli), while native catfish (Loricariichthys castaneus, Pimelodella lateristriga) occupied deeper areas. The fish distribution seems to be driven by local factors, such as oxygen availability and habitat structure. The preference for the littoral zone by alien cichlids may have led to the extirpation/decrease of native characids and induced catfishes to occupy deep habitats. Underwater drones can be a valuable tool for the simultaneous collection of abiotic/biotic data, especially in deep reservoirs with complex habitats, resulting in advances in the environmental monitoring of inland waters.