Trophic and limnological changes in highly fragmented rivers predict the decreasing abundance of detritivorous fish. (March 2020)

• Record Type: Journal Article
• Authors: Santos, Natália Carneiro Lacerda dos; Dias, Rosa Maria; Alves, Diego Corrêa; Melo, Brian Alvarez Ribeiro de; Ganassin, Maria Julia Mileo; Gomes, Luiz Carlos; Severi, William; Agostinho, Angelo Antonio
• Is Part Of: Ecological indicators. Volume 110(2020)
• Publication Date: 2020-03
• Subjects: Oligotrophication -- Serial dams -- Nutrient cycling -- Habitat fragmentation -- Bioperturbation -- Freshwater fish; Environmental monitoring -- Periodicals; Environmental management -- Periodicals; Environmental impact analysis -- Periodicals; Environmental risk assessment -- Periodicals; Sustainable development -- Periodicals; 333.71405
• DOI: 10.1016/j.ecolind.2019.105933
• Languages: English
• ISSNs: 1470-160X

Abstract

Highlights: Correlation between detritivorous fish and oligotrophication process was evaluated. There was a negative impact of the indicators on the oligotrophication process. Chlorophyll- a was the most negatively related indicator. Water residence time accumulated had a positive effect on oligotrophication process. Oligotrophication had a negative effect on detritivorous fish abundance. Abstract: The number of dams has had a significant increase in the last six decades, altering the physiography of rivers and creating systems of reservoirs in series. Therefore, it is expected that in a cascade of reservoirs, detritivorous fish will be especially affected due to the loss of nutritional quality in these regions, resulted from the high sedimentation of nutrients and organic matter. The objective of this study was to evaluate whether changes in the abundance of detritivorous fish, throughout a reservoir cascade in Brazil, resulted from trophic and limnological variations associated with sediment and nutrient retention. We used the Structural Equation Models approach (SEM) to test hypotheses. The six reservoirs studied are located in the São Francisco River, in the Northeast Brazil. The variables used to index latent variable oligotrophication were divided into trophic (total phosphate, nitrate and chlorophyll- a ) and limnological variables (turbidity and water residence time accumulated), and the abundance of the detritivore guild was indexed by the catch per unit effort (CPUE). Our results indicate a significant negative impact of the both trophic (total phosphate, chlorophyll- a and nitrate) and limnological indicators (turbidity) on the oligotrophication process. The longer residence times of the water accumulated along the reservoir cascade augment the oligotrophication process, consequently affecting negatively all the trophic and limnological indicators analysed. Finally, the latent variable oligotrophication had a significant negative effect on the latent variable detritivorous fish abundance throughout the cascade. The Curimatidae family was the most affected by oligotrophication along the cascade, followed by Prochilodontidae. These different responses to the detritivorous fish families reflect different patterns in the morphology of the oral apparatus and forms of food apprehension. Our findings are of particular importance for the management of fish species in highly fragmented rivers.