Riparian integrity affects diet and intestinal length of a generalist fish species

Abstract

Human activities in the riparian zone can affect the feeding of stream fish because they alter autochthonous production (periphyton, macrophytes and aquatic insects) and allochthonous inputs (terrestrial insects, leaves, seeds and fruits). In the present study we investigated how the diet and intestinal length of a persistent and generalist fish species (Bryconamericus iheringii, Characidae) responds to riparian modifications in 31 subtropical streams in southern Brazil. We hypothesised that intestinal length would be longer in populations inhabiting streams with converted riparian vegetation as a consequence of greater consumption of an indigestible and low-protein diet. Populations of B. iheringii from streams with a degraded riparian zone and reduced canopy cover had longer intestinal length (after accounting for body size), which was associated with decreased consumption of terrestrial plants and invertebrates and increased ingestion of filamentous algae, macrophytes and detritus. These results indicate that anthropic alteration of riparian zones and increased canopy openness trigger shifts in the diet and intestinal length of B. iheringii. The findings suggest that plasticity in intestinal length is an important characteristic to determine whether fish populations can persist in a variety of habitat conditions and cope with the digestion of a greater proportion of low-quality and low-protein food items in human-altered environments.

Morphological traits correlated with resource partitioning among small characin fish species coexisting in a Neotropical river

“…When correlated with dietary variables (PLS‐CA), these morphological traits were linked with its greater consumption of detritus and aquatic insects. It is important to note that similar feeding mechanisms were previously reported for other species of the same genus (Brandão‐Gonçalves, Lima‐Junior, & Suarez, 2009; Dala‐Corte et al, 2017; Oricolli & Bennemann, 2006; Russo et al, 2008). However, the presence of rudimentary gill rakers in this species and its having the smallest intestinal coefficient of all the species studied are strongly indicative that this species exhibits a comparatively greater tendency towards a carnivorous diet.…”

“…Nevertheless, these traits are not restrictive for the use of varied resources as they become available by co‐occurring species, so long as interspecific interactions do not interfere with them. This explains the previous reports of high trophic plasticity in species of the same genera in other Neotropical environments (Silva et al, 2014, 2017), as well as the success of these species in altered environments (Dala‐Corte et al, 2017; Delariva et al, 2013; Kokubun et al, 2018).…”

“…In all species examined, versatility in locomotory patterns permitted them to use both generalised and specialised feeding modes on a fairly wide variety of resources (from invertebrates to vegetal materials). Within the limits of their habitat, characins seem to be able to exploit all types of available resources, giving these fish exceedingly generalist trophic ranks (Dala‐Corte, Becker, & Melo, 2017; Delariva et al, 2013; Manna, Rezende, & Mazzoni, 2012; Pini et al, 2019; Portella et al, 2017; Silva et al, 2017). However, under conditions of species coexistence we found that resource partitioning occurred on finer scales.…”

Diet and body shape among populations of Bryconamericus iheringii (Otophysi: Characidae) across the Campos Sulinos ecosystem

“…Accordingly, in environments where macrophytes and algae were abundant, the species had a higher consumption of aquatic plants. Thereby, B. iheringii is considered a species that adapts to environmental alterations caused by anthropic impacts, since in the absence of items as insects, it forages on a high volume of detritus and algae (Dala-Corte et al, 2016b).…”

“…This broad area of riparian forest is what most contributed to a large comsumption of allochthonous plants by B. iheringii. However, if land exploration for livestock and soy production keeps rising, bigger morphological and dietary differences may become relevant (Allan, 2004;Dala-Corte et al, 2016b).…”