Underwater drones reveal different fish community structures on the steep slopes of a tropical reservoir

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 exotic), with all species occurring in the littoral zone, seven species in the transition, and four in the profundal zone. A greater fish abundance and richness was found in the littoral zone corroborating the main hypothesis. The littoral zone was dominated by exotic 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. Supplementary Information The online version contains supplementary material available at 10.1007/s10750-021-04790-9.

Unraveling trait‐based fish community assembly in tropical reservoirs

“…This FG included a mix of native species and non‐native cichlids, and visually oriented piscivores (mostly cichlid species) were favored in higher elevation, area, volume, and influence of river flow, as a primary consequence of the higher transparency and lower turbidity typical of larger reservoirs at upstream reaches in the PSR (Guedes & Araújo, 2022; Uehara et al, 2015). The littoral zone in the Lajes reservoir (isolated reservoir) is also characterized by higher temperature, oxygen concentration, and pH, and the substrate is covered by branches and leaves, environmental conditions strongly associated with its long water residence time (almost 300 days) (Franco et al, 2018; Guedes & Araújo, 2022). Therefore, the higher hydrological stability resulting from the long retention time most likely favors nest‐building fishes, which may largely explain the prevalence of non‐native species (omnivorous and piscivorous cichlids) in the group formed by the isolated and most channel reservoirs.…”

“…Other ecological traits were related to food acquisition and energy allocation for reproduction (Table 1, Table S2). Ecological information was obtained primarily from the FishBase online database (Froese & Pauly, 2022), complemented by several other sources (Costa et al, 2013; Guedes & Araújo, 2022; Luz‐Agostinho et al, 2008; Makrakis et al, 2012; Rocha et al, 2015; Santos et al, 2010) and our combined knowledge.…”

A Unified Approach to Modeling and Simulation of Underwater Vehicle Multi-Manipulator Systems

“…Angular velocity of frame O j relative to O n , denoted by ω n j/n , is calculated by the derivative of Equation (2), which lends to Equation (3):…”

“…In the last five years, Unmanned Underwater Drones (UUD) have become a standard tool for researching marine life, some examples of which include the monitoring, tracking, and imaging of a randomly moving shark [1] and the study of a school of fish in an altered environment, as carried out in the tropical reservoir (oligo-mesotrophic and warm monomictic) located in southeastern Brazil [2]. However, although underwater drones are a valuable tool for data collection and are becoming less expensive, they still have limitations due to possible equipment effects, such as different light intensities and the artificial noise, speed, size, and depth of the vehicle, resulting in the alteration of the behavior of the species to be studied.…”

Finding navigation cues near fishways

“…Aerial drones have been used in mapping the migration of naked carp ( Gymnocypris przewalskii ) (Zhang et al ., 2022) and to map flow velocities around fishways or migration barriers (Timm et al ., 2019; Strelnikova et al ., 2020). Underwater drones have been used to assess fish communities along depth gradients (Guedes & Araújo, 2022). One advantage of the use of cameras over tagging is that invasive tagging procedures are not needed.…”