Assessment of changes in the ichthyofauna in a tropical reservoir in south‐eastern Brazil: Consequences of global warming?

Abstract

Increases in temperatures over the last century, more intensively after the eighties, were recorded in several databases for the south‐eastern Brazil. These increases are likely to change fish communities in aquatic systems by decreasing abundances, biomass and sizes of some species more sensitive to climate change. Reservoirs may be particularly susceptible to the effects of climate change, as they isolate previously connected areas limiting fish dispersal and migration, as well as increasing water temperature and thermal stratification. We assessed temporal changes in the abundance and biomass of the ichthyofauna in an isolate reservoir (inflowing waters from small tributaries in a highland region) aiming to associate changes with climate effects over three decades (1990, 2000, 2010). Two abundant native species, a loricariid Loricariichthys castaneus (Castelnau, 1855) and a cichlid Geophagus brasiliensis (Quoy & Gaimard, 1824), were selected to assess eventual response to climate changes in their geographical distribution in the Southeast Atlantic Hydrographic Region, considering different carbon emission scenarios using ecological niche models. A decrease in the densities and biomass of the ichthyofauna and of the two selected species were observed in both summer and winter over the three decades, coinciding with increases in temperatures. These decreases were correlated with increases in positive anomalies of temperature, which may be an indicator of climatic changes, although with low explanation of the data variation. The mean size of L. castaneus decreased between the nineties and 2010, whereas no significant trend was found for the size of G. brasiliensis. Our predictions of new area for future adequacy indicated a loss in the distribution area for both species (mainly for G. brasiliensis), considering the most pessimistic scenario for 2050 and 2070, possibly due to climatic changes. Both hydroelectric dams and global warming pose threats to freshwater fish diversity, and both will interact. Changes observed in the fish assemblage over the last decades were essential for an assessment of the consequences of global warming in this type of reservoir combining larger scale studies with future projections.

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

“…The structure of the fish assemblages observed with ROV was substantially different from those previously observed with gillnets in the Lajes Reservoir. Catches with gillnets (deployed at the margins during the night period) showed L. castaneus as the most abundant species, followed by the cichlids C. rendalli and C. lacustris, with relatively intermediate abundance, and P. lateristriga as a low frequent/rare species (Araújo & Santos, 2001 ; Guedes et al, 2020 ; Araújo et al, 2021 ). However, the aforementioned estimates are invariably skewed for different reasons.…”

“…The water retention time (− 300 days) and water transparency (euphotic zone = 9.2 m) are high, with predominance of oligo-mesotrophic conditions (Soares et al, 2008 ; Klippel et al, 2020 ). Lentic conditions predominate in the longitudinal extent of the reservoir associated with the high retention time (Araújo et al, 2021 ). The water column presents thermal stratification typical of warm monomictic water bodies, with a stratified warm period, and mixing (complete or partial) during the cold period (Branco et al, 2009 ).…”

Capacity Assessment Spatialization to Disaster Risk Reduction in Semarang Coastal Area

“…Global warming has been serious issue and problem to human civilization nowadays and has to be considerations in environment management [1][2][3]. IPCC (Intergovernmental Panel Climate Change) estimates that earth average temperature will be increasing by 1,5 ˚C in 2030-2050 [4].…”