Fish Assemblages in Pampean Streams (Buenos Aires, Argentina): Relationship to Abiotic and Anthropic Variables

Abstract

The present study reported the effect of natural and anthropic environmental variables on the fish assemblages in the pampean streams, in the coastal strip along the Río de la Plata, Buenos Aires province, Argentina. Five streams were sampled at 12 sites surrounded by land devoted to different uses. A correspondence analysis sorted the streams into two groups: a less impacted group formed by sites surrounded by livestock-raising pastures and a more impacted one passing through urban sites and including a stream adjacent to a modest rural urbanization with a dairy in the stream's basin. The nutrient concentrations were significantly higher in the more impacted group; with species richness, diversity, abundance, and biomass being significantly lower. A canonical-correspondence analysis linked the more impacted sites to high concentrations of soluble reactive phosphorus and impoverished fish assemblages, composed of species tolerant to environmental pollution. On the other hand, sites with higher oxygen concentrations and pH were related to richer assemblages pointing to good environmental conditions at the sites surrounded by livestock-raising pastures. The downstream sites on the less impacted streams contained fish assemblages in which the juvenile stages of species corresponding to the Río de la Plata were dominant.

Fish assemblage structure in a Neotropical urbanised prairie stream exposed to multiple natural and anthropic factors

“…These changes are strongly associated with the drastic impacts that cities and industries impose on different aspects of the ecological integrity of these vulnerable fluvial ecosystems. This is a global pattern (Boët et al, 1999; Gagny et al, 2000; Jackson et al, 2001) also observed in Neotropical urban streams (Alexandre et al, 2010; Cunico et al, 2006; Daga et al, 2012) and, recently, in Pampa streams (Paracampo et al, 2020). Worldwide, the total urban land use occupies low extensions, but still have disproportionately large effects on the biota (Paul & Meyer, 2001) and particularly in the fish community (Fausch et al, 1990).…”

“…In fact, the abundance of this species was one of the most important metrics characterising the differences between fish assemblages from contrasting environmental conditions. Similarly, this species was also dominant in regional urban ecosystems, the Suquía River near Córdoba city (Hued & Bistoni, 2005) and Pampa streams from the populated coastal drainages of the Río de la Plata (Paracampo et al, 2020). The relative abundance of tolerant species increases with urbanisation (Paul & Meyer, 2001).…”

“…Particularly, this species is highly tolerant to hypoxia because the use of the caudal portion of the intestine as an accessory air‐breathing organ (Plaul et al, 2016). Among water quality variables, dissolved oxygen is perhaps the most influential aspect for fish assemblages in impacted ecosystems (Boët et al, 1999; Daga et al, 2012; Paracampo et al, 2020). Fish species tolerant to hypoxia became abundant in oxygen‐poor waters by means of their special behaviours or physiologic adaptations (Ferreira & Casatti, 2006).…”

“…In the Neotropical region, changes in water conductivity, concentrations of dissolved oxygen and total phosphorus affected the composition and structure of stream fish assemblages of urban streams from the upper Paraná River (Daga et al, 2012). Most impacted streams of the Pampa Plain, with high concentrations of phosphorus, showed impoverished fish assemblages, composed of species tolerant to environmental pollution (Paracampo et al, 2020). Similarly, increasing land use intensity produced that oligotrophic streams of Uruguay were characterised by a higher evenness, larger individuals and at least 40% of sensitive species, while eutrophic reaches showed the opposite community features with less than 20% of sensitive species (Chalar et al, 2013).…”

Longitudinal and temporal variation in fish assemblage structure along lowland prairie Neotropical streams and their relationship with environmental variables

“…The species were identi ed following Azpelicueta and Braga (1991), Braga (1993) In order to evaluate the temporal persistence of longitudinal variation patterns in the sh assemblage structure, we compare sh data obtained during the present study (period 2019-2020) with historical data obtained ten years ago (period 2009-2010) at El Pescado stream (P1, P2 and P3), hereafter referred to as decadal analysis. During both periods the data were obtained employing similar shing efforts (Paracampo 2015;Paracampo et al 2020). Since during the 2009-2010 period a single sample was available per site, the three samples of each site taken during the 2019-2020 period were averaged before performing the decadal analysis.…”