Extreme drought events and the sustainability of fish farming in net cages in reservoirs of the semi-arid northeastern region in Brazil

Abstract

Reservoirs play important roles in local socioeconomic development and are particularly relevant in developing countries. The rearing of Nile tilapia (Oreochromis niloticus) in cages is one of the fastest growing activities carried out in reservoirs since it is a strategy to sustain the growing demand for food fish. Most reservoirs are in eutrophic or hypereutrophic conditions in the semi-arid northeast region of Brazil and thus, the expansion of aquaculture endangers the ecological functions of the reservoirs by increasing the eutrophication potential. On the other hand, aquaculture contributes to economic development by generating jobs and income for the population and being an important alternative in the production sector for riverine populations. In this context, we present in this article our opinion about the sustainability of fish farming activities in net cages in reservoirs of the Brazilian semiarid, especially when subjected to extreme drought events.

Abiotic factors driving cyanobacterial biomass and composition under perennial bloom conditions in tropical latitudes

“…Finally, our results raise a public health concern regarding the use of the studied lakes for fish cage production as intended. The introduction of fish food in the systems increases nutrient input, which will likely increase the risk of eutrophication in the lower trophic state lakes (Gorlach-Lira et al, 2013;Henry-Silva et al, 2019). While we did not measure cyanobacterial toxicity here, microcystins from Microcystis and saxitoxins from Raphidiopsis are widely reported from other lakes within the same semiarid region of the state of Rio Grande do Norte where the study lakes are, and also from Brazilian Semiarid lakes in general (Molica et al, 2005;Bittencourt-Oliveira et al, 2014;Fonseca et al, 2015;Lorenzi et al, 2018;Moura et al, 2018).…”

Impacts of the Residual Trace Metals of Aquaculture in Net Cages on the Quality of Sediment

“…Henry-Silva, Melo-Júnior and Attayde [ 82 ] reported that in the Umari Reservoir, RN, Brazil, a heavy summer rain event cooled the water temperature, breaking the thermal stratification and causing turbulent vertical circulation. This event triggered sediment suspension and the complete mixing of the water column.…”

“…According to Henry-Silva, Melo-Júnior and Attayde [ 82 ], Melo-Júnior and Campeche [ 69 ] and Melo-Júnior and Sampaio [ 83 ], vertical circulation processes are common in semiarid reservoirs. Circulation events allow the oxygenation of the sediment which contributes to the dispersion of trace metals in the environment.…”

Editorial: Freshwater sustainability and aquatic ecology in a fast-changing world

“…In addition to concerns about the introduction of species, Garcia et al (2019) discuss the deleterious effects of introducing fish parasites, which would not occur under natural conditions, and how this introduction can directly affect native fish fauna. Likewise, it is worrisome how the production of exotic fish species can cause environmental damage such as eutrophication (Henry-Silva et al, 2019;Camargo & Amorim, 2020). In two related opinion pieces, Camargo & Amorim (2020) contend that fish farming in cages should be restricted in Brazil, whereas Henry-Silva et al (2019) discuss practices and conditions that can affect the sustainability of fish farming in cages of reservoirs in Brazil's semiarid region.…”