Rainbow Trout diets and macroinvertebrates assemblages responses from watersheds dominated by native and exotic plantations

Abstract

Over the past few decades, land-use changes through conversion of global forest cover to exotic plantations is contributing to both habitat and biodiversity loss and species extinctions. To better understand human influences on ecosystem, we use diet composition from introduced Rainbow Trout Oncorhynchus mykiss as indicator of potential changes in the composition of stream-macroinvertebrates due to land use changes from native to exotic vegetation (eucalyptus plantations) in southern Chile. Water quality variables, aquatic macroinvertebrates and Rainbow Trout diet were studied in 12 sites from mountain streams located in two watersheds including one dominated by native riparian vegetation and the other dominated by exotic vegetation. As expected, richness and abundance of macroinvertebrates were clearly higher at sites in native forest than in those with exotic vegetation. Collector-gatherer was the most abundant functional feeding group, but there was no statistical difference in the functional composition between the two watersheds. Differences in in-stream macroinvertebrate availability was more higher correlated with changes in Rainbow Trout diets. Specifically, taxa consumed from the watershed dominated by native forests was higher than from the watershed with exotic vegetation. Additional environmental variables showed statistical differences between watersheds. The exotic vegetation sites had the highest concentrations of dissolved solids, suspended solids, nitrates, chlorides and sulphates. Our findings show that macroinvertebrate assemblage structure and trout diets can be altered by changes in riparian vegetation. The absence of specific macroinvertebrate taxa in streams with exotic vegetation was captured by the composition of trout diets. This suggest that Rainbow Trout diets can be a good biological indicator of land use practices and thus, diet can be used as a rapid and effective tool for evaluate environmental quality. Our findings provide insights about the design of aquatic monitoring programmes to improve detection of anthropogenic impacts in streams in South America and elsewhere.

First report of inventory and role of macroinvertebrates and fish in Cautín river (38° S, Araucania region Chile)

“…The literature seems to indicate that benthic invertebrates would have a marked gradient in heterogeneity as a function of the gradient in water conditions of the Cautin river ( Figure 1), as in this aspect it is similar to existing descriptions of other Patagonian rivers (Arenas, 1995;Figueroa et al, 2003Figueroa et al, , 2007Figueroa et al, , 2010Figueroa et al, , 2013Fierro et al, 2012Fierro et al, , 2015Fierro et al, , 2016Encina et al, 2017). Previous reports thus indicate that the taxa Plecoptera, Ephemeroptera and Trichoptera larval stages and Aegla are abundant under turbulent flow, associated with a high oxygen concentration and much particulate matter that makes a food source (Oyanedel et al, 2008;Moya et al, 2009).…”

“…Smith), freshwater crabs of the genus Aegla (Leach, 1820), and the southern Chilean river prawn, Samastacus spinifrons (Phillippi, 1882) (De los Ríos-Escalante et al, 2012;Jara, 2013;Rudolph, 2013), and Diptera, Trichoptera and Ephemeroptera larval stages (Figueroa, 2000;Figueroa et al, 2003Figueroa et al, , 2007, many of these groups are currently endangered due to human-induced alterations in their habitats and the introduction of alien salmonids species since 1914 (Golusda, 1907(Golusda, , 1927Barros, 1931;Jara et al, 2006;Encina et al, 2017;Vega et al, 2017). The (introduced) salmonids, specifically, constitute non-selective, active predators (Soto et al, 2006(Soto et al, , 2007Fierro et al, 2012Fierro et al, , 2015Fierro et al, , 2016Piedra et al, 2012;Valdovinos et al, 2012;Vargas et al, 2010Vargas et al, , 2015. Also, some rivers of this kind have undergone alterations in their surrounding drainage basins, viz., through anthropogenic enterprises as agriculture, deforestation, forestatation, growing cities, industry, among others, these new conditions affect the water quality (Kristensen et al, 2009), and, by consequence, also the benthic species that are sensitive to water pollution are affected in their abundance (Figueroa et al, 2003(Figueroa et al, , 2007Tello et al, 2010;Vega et al, 2013Vega et al, , 2017Gorski et al, 2015;Nimptsch et al, 2015).…”

Macroinvertebrates and Fishes as Bioindicators of Stream Water Pollution

“…Furthermore, recent studies report that the stomach contents of salmonids (i.e., Oncorhynchus mykiss and Salmo trutta) contain a diversity of invertebrate prey present in the benthos of nonintervened (hereafter termed "native") basins, thereby reflecting anthropogenic impacts to the basin [26]. Related to this, Fierro et al [6] reported similarities in stomach contents and prey diversity of the benthos in river sections with land use different than in the basin.…”

“…Worldwide, a primary threat to freshwater ecosystems is the rapid changes occurring in land uses (Figure 1), a situation that has intensified over the past decade [5,6]. Most recent land use conversion has been for crop production, which notably impacts proximal ecosystems due to changes over extensive crop areas [7].…”

Application of the Lake Biotic Index (LBI) in the ecological characterization of a North Patagonian lake in Chile

“…Bioindicators of environmental impact based on benthic macroinvertebrates gained special relevance in Europe (Dermott and Pachkevitch, 2012). However, in Chile and South America they are mostly used to assess the ecological condition of rivers (Brand and Miserendino, 2015;Cardoso and Novaes, 2013;Correa-Araneda, 2016;Correa-Araneda et al, 2010;Dedieu et al, 2016;Dos Santos, 2017;Fierro et al, 2016;Figueroa et al, 2003;Kay et al, 2001;Lallement et al, 2014;Luo et al, 2018;Meza-S et al, 2012;Miserendino et al, 2012;Nascimento et al, 2018).…”