Abstract
This study described the use of food resources and the distribution of fish trophic guilds along the longitudinal gradient of a coastal Atlantic stream, southern Brazil. Allochthonous resources (terrestrial insects) predominated in the headwaters, whereas autochthonous food items (algae, fish) and detritus predominated in the mouth section. Detritivorous, aquaticinvertivorous, and terrestrial- and aquatic-insectivorous species occurred throughout the gradient, while omnivorous and piscivorous in the headwaters and middle stretches, respectively, and herbivorous in the middle and mouth. Detritivores and aquatic-insectivores were significantly more specialized than the other guilds, however, there was no evidence of a longitudinal increase in trophic specialization. Density and biomass of aquatic-invertivores and aquatic-insectivores decreased, whereas that of detritivores increased longitudinally. The distribution of trophic guilds was significantly associated with the stream section, where aquatic and terrestrial insectivorous were more frequent in rocky and flowed stretches from the headwater and detritivores in deeper environments with finer particles of substrate from the mouth. This suggests that fish assemblages in coastal streams with a steep longitudinal gradient may follow patterns in the use of food resources according with the food availability along the river, as predicted by the River Continuum Concept.
Highlights
Longitudinal patterns in richness and composition of trophic guilds of stream fish and macroinvertebrate assemblages have been consistently documented along size continuum of rivers (Ibanez et al, 2007), what have leave some authors to stress about possible mechanistic processes spatial for the structuring and functioning of aquatic communities (Vannote et al, 1980; Ward, 1989; Junk et al, 1989; Rice et al, 2001; Brenden et al, 2008). These patterns are usually attributed to changes in physical conditions of streams or rivers from upstream to downstream areas creating strong constraints on assemblage structure linked to food availability
Study area This study was conducted in the Vermelho River, in the eastern Atlantic basin of Brazil (Fig. 1)
This river lies within the boundaries of the newly established “Reserva Particular do Patrimônio Natural” (RPPN) Morro da Mina, between the coastal municipalities of Antonina and Morretes in the state of Paraná, southern Brazil
Summary
Longitudinal patterns in richness and composition of trophic guilds of stream fish and macroinvertebrate assemblages have been consistently documented along size continuum of rivers (Ibanez et al, 2007), what have leave some authors to stress about possible mechanistic processes spatial for the structuring and functioning of aquatic communities (Vannote et al, 1980; Ward, 1989; Junk et al, 1989; Rice et al, 2001; Brenden et al, 2008) These patterns are usually attributed to changes in physical conditions of streams or rivers from upstream to downstream areas creating strong constraints on assemblage structure linked to food availability (the River Continuum Concept - RCC; Vannote et al, 1980). 5790, Bloco G90, Campus Universitário, 87020-000 Maringá, Paraná, Brazil
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