From forests to cattail: how does the riparian zone influence stream fish?

Abstract

The aim of this study was to verify whether taxonomic and functional composition of stream fishes vary under three different preservation conditions of riparian zone: preserved (PRE), intermediate condition (INT), and degraded (DEG). Five stream stretches representing each condition were selected. Samples were taken from each stream in three occasions during the dry seasons from 2004 to 2007. Electro fishing (PRE and INT), sieves, dip nets, and hand seines (DEG) were used according to the characteristics of each sampled site. Overall, 46 species were registered. Differences in the taxonomic and functional species composition among groups were found, following the condition of riparian zones. The ichthyofauna recorded in the PRE was typical to pristine environments, consisting of species with specialized habits, notably benthic insectivores, intolerant, and rheophilics. In the INT group, replacement of riparian forest with shrubs and/or grasses created environmental conditions which favor the occurrence of tolerant species but also harbor a residual fauna of sensitive species. DEG streams presented mostly detritivores, tolerant, small sized fishes which occupy the surface and preferred slow water flux. Changes in the species composition were represented by the occurrence and dominance of tolerant species in detriment of the more sensitive and specialist species, following the gradient of degradation in the riparian zone. Forested streams act as unique habitats to many specialized species and it can be presumable that the degradation of riparian vegetation can generate biotic homogenization which may reduce species diversity and ecosystem services.O presente estudo verificou se a composição taxonômica e funcional de peixes de riachos varia ao longo de três condições de preservação da zona ripária: preservada (PRE), preservação intermediária (INT) e degradada (DEG). Cinco riachos de cada grupo foram selecionados e amostras foram obtidas em cada riacho em três ocasiões em períodos secos de 2004 a 2007. Pesca elétrica (PRE e INT), peneiras, puçás e redes de arrasto (DEG) foram usados de acordo com as características de cada local de coleta. No geral, 46 espécies foram registradas. Foram registradas diferenças na composição taxonômica e funcional de espécies entre os grupos, seguindo o gradiente de degradação da zona ripária. A ictiofauna encontrada em PRE foi típica de ambientes prístinos, consistindo em espécies de hábitos especializados, notavelmente bentônicas, insetívoras, intolerantes e reofílicas. No grupo INT, a substituição da floresta ripária por herbáceas ou gramíneas cria condições ambientais que favorecem a ocorrência de espécies tolerantes, mas também abriga uma fauna residual de espécies sensíveis. O grupo DEG foi representado principalmente por espécies detritívoras, tolerantes e de superfície. As modificações na composição de espécies foram representadas pela ocorrência e dominância de espécies tolerantes em detrimento da redução/eliminação daquelas mais sensíveis e especializadas, acompanhando o grad...

Fish-based Index of Biotic Integrity for wadeable streams from Atlantic Forest of south São Paulo State, Brazil

“…Based on the literature (Oyakawa et al, 2006;Casatti et al, 2012) species were categorized into trophic group, position in the water column and preference for rapid meso-habitats (Table 2). Seventeen metrics were considered to define the list of candidate metrics of the IBI (Table 3).…”

Variation in the diet of a small characin according to the riparian zone coverage in an Atlantic Forest stream, northeastern Brazil

“…and KARR, JR. 1983 an increase in the amount of algae, macrophytes and debris. The presence of material of plant origin and a large variety of invertebrates, especially insects, are evidence for the omnivorous diet of Astyanax vermilion, that has a tendency towards insectivory, a condition that has been widely reported for species of the genus (Casatti et al, 2012;Castro and Casatti, 1997;Ferreira, 2007;Luiz et al, 1998).…”

“…This includes streams located in the Atlantic Forest (Menezes et al, 2007). These human actions generate great environmental impacts for stream structure (Lorion and Kennedy, 2009) and ichthyofauna (Casatti et al, 2012), making it difficult to maintain the integrity of these ecosystems Casatti et al, 2006). These alterations are particularly critical because, in headwater streams, the availability of resources, especially food, depends mostly on the surrounding environment, which is constantly providing organic and inorganic matter (Benstead et al, 2003;Pusey and Arthington, 2003;Allan, 1995;Lorion and Kennedy, 2009).…”

Effect of the riparian vegetation removal on the trophic network of Neotropical stream fish assemblage

“…Several studies (Allan, 2004;Casatti et al, 2006;Casatti et al, 2012) have showed the importance of riparian vegetation to the physical structure of streams, which can favor the maintenance of environmental stability and provide nutrients used through the trophic chain. Also, Rezende and Mazzoni (2005) have showed that in streams with riparian vegetation the input of allochthonous matter can change seasonally, with a higher input of animal-and vegetal matter during the wet season.…”

“…Many studies (Bojsen and Barriga, 2002;Casatti, et al, 2012;Teresa and Casatti, 2012) have also showed the effects of riparian vegetation suppression on fish assemblage; i.e., it leads to their simplification, with a high dominance of tolerant species and loss of ecosystem services. Moreover, Casatti et al (2015) have found that although environments without riparian vegetation may have higher richness and diversity of fish, they also have a high functional redundancy, mostly related to feeding.…”