Persistence and instability typify the fish assemblage structure of Rio Ubatiba, a Neotropical stream of South-east Brazil

Abstract

The objective was to explore levels of persistence and stability of a Neotropical fish assemblage in a typical Serra do Mar stream (Southeast Brazil) over 1994-2008 with 90 quantitative samples in total. All along the stream gradient, the fish assemblage was composed of small-sized, short living species including benthic and water column species. Only four species occurred at the uppermost site (i.e., S1) whereas these four species plus eight species occurred at all other sites. In regards to species presence-absence, all species were temporally persistent at all sites over the study years. Overall, all species were abundant across scales of space and time with only three out of 14 species showing consistently low densities along the stream across years. Nevertheless, as indicated by the temporal variations in the Coefficients of Variation (CV%), the fish assemblages were highly unstable at all sites over time. At all sites the CV% varied widely and increased significantly over the years. No consistent density-dependence was elucidated nor any significant correlation among environmental variables and assemblage attributes were detected. The only consistent relationship elucidated relates the CV% of assemblage variability over time and the CV% of the ratio between stream discharge in the two major seasons, May and November.

Temporal dynamics of freshwater fish assemblages, their background and methods of quantifications—A synthesis

“…Studies on long‐term fish assemblage dynamics have also been intensively studied in some tropical and subtropical areas (e.g. Brazil) (Dittrich et al., 2016; Lobon‐Cervia et al., 2016), which is critically important as many of these regions maintain a high level of biodiversity (Agostinho et al., 2005). Due to the methodological heterogeneities among the studies, it was hard to evaluate the exact role of region in determining temporal variability.…”

Predation effects on matrotrophy, superfetation and other life history traits in Phalloceros harpagos

“…Phalloceros harpagos , an abundant poeciliid previously classified as Phalloceros caudimaculatus , is found over the middle and upper Ubatiba stream (Aranha & Caramaschi, ). One of its major predators is the piscivorous wolffish Hoplias malabaricus (Bloch 1794) (mean standard length: 134 ± 62 mm), which largely feeds on poeciliid species (Lobon‐Cervia, Mazzoni, Iglesias‐Rios, & Caramaschi, ; Mazzoni & Costa, ). Hoplias malabaricus prefers to attack shoals of poeciliids over a single prey, and despite being generally regarded as a nocturnal predator, H. malabaricus is active and readily feeds on poeciliids during the day (Botham & Krause, ).…”

“…Three sites-100 m long each-were initially selected based on data on P. harpagos predation intensity from previous studies (Lobon-Cervia et al, 2015). We then estimated fish densities for each of the three selected sites with electrofishing techniques (Mazzoni, Fenerich-Verani, & Caramaschi, 2000) using the three-pass removal method (Zippin, 1958) ( Feeding studies on Phalloceros species have shown that algae are their primary food resource (e.g., Aranha & Caramaschi, 1999;Costa, 1987).…”