Abstract
Abstract The use and occupation of land by human population substantially influence environmental variables and fish assemblage in streams. However, there is little knowledge on how these changes affect the ecomorphological structure of fish assemblage in mesohabitats. Therefore, we aim to assess whether the land-use types affect the ecomorphological structure of fish assemblage in distinct mesohabitats. Environmental and ichthyofaunistic data were collected in three mesohabitats (rifles, runs, and pools) of five rural and five urban streams. Twenty-one ecomorphological indices were obtained from the mean of linear morphological measurements and areas of the fishes. Subsequently, the Euclidean distance was calculated, based on the ecomorphological indices, between each pair of species, to measure the ecomorphological distances for the mesohabitats of the rural and urban streams. The results show that the urban environment is more harmful to streams than the rural one, due to changes in the environmental variables and decrease in species richness. The main environmental changes found in urban streams were the decrease in canopy cover by riparian vegetation and dissolved oxygen, and the increase in electrical conductivity and bed silting. Also, there was a significant decrease in the morphological similarity between fish species in the mesohabitats of urban streams compared to rural ones. Therefore, we can conclude that the urban environment leads to the loss of morphologically similar fish species in the mesohabitats, with only a few functionally distinct species remaining.
Highlights
The alteration of natural landscapes caused by anthropogenic activities is one of the greatest threats to biodiversity worldwide (Sala et al 2000, Foley et al 2005)
The use and occupation of land by the human population, such as rural and urban landscapes, are responsible for influencing several environmental factors of streams, such as hydrology, channel morphology, and water quality and toxicity (Allan 2004, Walsh et al 2005, Cunico et al 2012). Both rural and urban landscapes cause environmental damage to streams (Tóth et al 2019), comparative studies have shown that the urban environment is generally more harmful to stream fish assemblages than the rural one (Cunico et al 2006, 2012, Alexandre et al 2010, Cruz & Pompeu, 2020)
The effects of the land use on fish assemblages are still largely evaluated only by metrics that consider the number of species and their abundance (Weaver & Garman 1994, Wang et al 2001, Walsh et al 2005, Cunico et al 2006, 2012, Tóth et al 2019)
Summary
The alteration of natural landscapes caused by anthropogenic activities is one of the greatest threats to biodiversity worldwide (Sala et al 2000, Foley et al 2005). The use and occupation of land by the human population, such as rural and urban landscapes, are responsible for influencing several environmental factors of streams, such as hydrology, channel morphology, and water quality and toxicity (Allan 2004, Walsh et al 2005, Cunico et al 2012) Both rural and urban landscapes cause environmental damage to streams (Tóth et al 2019), comparative studies have shown that the urban environment is generally more harmful to stream fish assemblages than the rural one (Cunico et al 2006, 2012, Alexandre et al 2010, Cruz & Pompeu, 2020). It is necessary to use the functional characteristics of the species as a complementary approach to assess the impact of land use on the fish assemblage, instead of only taxonomic identity (Brown et al 2009, Cunico et al 2011, Kern & Langerhans 2018)
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