How Limnological Variables Influence the Occurrence and Abundance of a Visual Predator in an Invaded River-Floodplain System

Abstract

Environmental characteristics of an invaded environment can predict the invasion success of a species, depending on its habits and life strategies. Cichla kelberi is a visual and voracious predator introduced in the upper Paraná River floodplain, an area that suffers with several upstream dams that caused many environmental changes over the years (e.g. increased water transparency). As this species is a pre-adapted species to environments that presents high water transparency, our main goal was to test the hypothesis that variables related to the underwater visibility would be important drivers of the successful invasion of C. kelberi in the upper Paraná River floodplain. We predict that turbidity (proxy of water transparency) is one of the major limnological determinants of occurrence and abundance of C. kelberi. Individuals of the invasive species and seven limnological variables were sampled quarterly between February 2000 and November 2018. This long-term data is part of the sixth site of the Brazilian Long Term Ecological Program (PELD). We fitted two regression models to all occurrence and abundance data (response variables) against the limnological variables (explanatory variables). For occurrence data, we fitted a Generalized Linear Mixed Model and for abundance data, we fitted a Linear Mixed Effects Model. The occurrence data of C. kelberi showed that turbidity and dissolved oxygen were the variables that most influenced the presence of this species, negatively and positively, respectively. The abundance data showed that dissolved oxygen and concentration of chlorophyll-a were the ones that most influenced the abundance of this species, negatively and positively, respectively. Our findings showed that besides turbidity, other limnological variables were also determinants for the occurrence and abundance of C. kelberi. Therefore, our results provided important

Fish on Fire: Shifts in Amazonian fish communities after floodplain forest fires

“…In addition, higher light penetration in the aquatic environment of fire scars could increase visibility and hunting success of diurnal, visually oriented predatory fishes, such as S. gouldingi , which in turn could influence local fish assemblages (Rodríguez & Lewis Jr, 1997). Higher visibility has also been suggested as an explanation for the increased abundance of predatory fish in natural habitats and in newly created reservoirs after hydropower dam constructions (Melo et al, 2009; Rodrigues et al, 2020). Lower food availability and higher predation risk may thus reduce the abundance of smaller‐size fishes in fire scars compared to unburnt forests.…”

Environment–ichthyofauna relations in a neotropical reservoir through a joint remote sensing/field sampling approach

“…For example, the results demonstrated that the abundance of piscivores decreased with higher turbidity values in the fluvial zone, and increased by the increment of this variable in the lacustrine zone. In the fluvial zone, turbidity may have acted directly reducing the success of prey capture, since most species of this guild rely on sight to capture food (Guthrie, 1986; Ranaker et al, 2012; Rodrigues et al, 2020). In the lacustrine zone, however, greater flow may have resulted in a process of water fertilisation, which in turn may have increased prey availability for piscivores, apparently in a bottom‐up process (Medeiros et al, 2014; Pinto et al, 2011; Thomas et al, 2007).…”