Data for: Richness, food webs structures and ecosystem functioning
Data files
Dec 11, 2022 version files 665.51 KB
-
qb.csv
-
README.txt
-
spatial.csv
-
trophic.csv
Abstract
This dataset has information on the spatial distribution of fish species from the middle Paraná River and the diet information of 15 fish-eating species. The objective of the paper was to evaluate the relationship between richness, the structure of food webs and standing biomass. In addition to the information on diet and spatial distribution, there is a readme file, two Rstudio scripts and an R environment (all the results of the work can be found in the latter).
Methods
The methodology was extracted from (DOI: 10.1111/1365-2656.13784)
Fishes were sampled from 27 water bodies (Figure 1) grouped in four habitat types according to their flow, size and connectivity: major rivers, secondary channels, connected lakes and isolated lakes. The major rivers consisted of lotic environments that had an average width between 330 and 1,100 m. The secondary channels had an average channel width between 28 and 137 m, and meandered among the floodplain islands. The connected lakes were lentic environments that had a permanent connection with the smaller and larger channels and had a surface area between 3.4 and 240 ha and a depth between 0.7 and 3.1 m at average water level. The isolated lakes consisted of lentic environments whose connection with the channels was interrupted throughout the hydrological period and presented areas between 4.1 and 40.1 ha. Given that ecological communities of the Paraná River floodplain vary at multiple spatial and temporal scales, it is logistically impossible to catch the whole variation in species occurrences and trophic interactions in a single sampling design. For this reason, we used two different but complementary sampling designs, one focusing on the spatial variation and another one focusing on temporal variation. In the first sampling design, we surveyed 27 different water bodies in four different occasions with an annual frequency during the years 2013, 2014, 2015 and 2016. The four spatial sampling events were timed to cover the four different hydroclimatic conditions. In the second sampling design, we surveyed four water bodies in 14 occasions with a bi-monthly frequency between 2015 and 2017 (total samples: 152 communities). Given that the study spanned periods of high and low waters during warm and cold seasons, each of the 18 surveys fell within one of four different hydro-climatic conditions: low waters, cold season; high waters, cold season; low waters, warm season and high waters, warm season. In this design, we considered hydrometric variability and thermal seasonality because they are the main temporal drivers of fish assemblage composition and ecosystem functioning (Scarabotti et al., 2017). This lassification properly captures the similarity in environmental conditions among surveys with similar hydro-period and thermal conditions (see Table S1). Samplings were classified in cold (autumn and winter; April to September) and warm periods (spring and summer, October to March) and in low water (below overflow level) and high water periods (above overflow level), totalling four different combinations of climatic and hydrologic conditions: high waters–cold season (HC), high waters–warm season (HW), low waters–cold season (LC) and low waters–warm season (LW). We used an overflow level of 3.42 m at the Paraná city gauge station (Scarabotti et al., 2017). Fish were collected using both gillnets and beach seine nets. We deployed two gillnet batteries, each one of 80 m long × 1.7 m high, composed of eight panels of 10 m long with different mesh sizes (30, 42, 54, 70, 90, 110, 130 and 160 mm between opposed knots) for 12 h (dusk–dawn). Piscivorous fishes were captured and euthanized in the field by medullary denervation after percussive stunning. Each individual was identified, measured and weighed. The stomachs were preserved in 10% formalin and examined in the laboratory under a binocular microscope. Fish prey items were identified at species level, whereas the invertebrate preys were identified at order level. Fish samplings were approved by the Ministry of Environment of the Santa Fe province (resolution 036/18) and followed the ethical guidelines and policies of the National Research Council of Argentina (CONICET, 2005).
Usage notes
Rstudio is necessary to open the scripts and be able to visualize the objects.