Quantifying fish species richness and abundance in Amazonian streams: assessment of a multiple gear method suitable for Terra firme stream fish assemblages

Abstract

A multigear sampling method to quantify fish richness and abundance in Amazonian Terra firme streams was assessed. This method is based on the four‐pass removal method using the combined application of different nets. The efficiency of the method was explored over 10 replicated sites along three streams over day, night and seasons. Use of four successive passes allowed both abundant and rare species to be collected and the abundance of common species to be estimated. On average, a high proportion (41%) of rare species was collected per sample (only one or two individuals) after four fishing passes. The efficiency of the sampling method to detect species richness per sample between successive passes was estimated using an autosimilarity approach. Although species richness and abundance increased with successive passes, no major differences were obtained between the third and fourth pass. A single pass considerably underestimated the richness and abundance of species in these type of streams, and night sampling also increased beta‐diversity by at least 20%. Abundance estimates demonstrated high efficiency with an overall sampling error of only 8 and 11% for samples and single species, respectively. Capture efficiency differed among fish species exhibiting different ecological traits and showed significant differences among seasons for total samples. Results supported the robustness of the method and its suitability to quantify fish richness and abundance in small, wadeable Amazonian Terra firme streams inhabited by highly diverse fish assemblages.

Unlocking biodiversity and conservation studies in high‐diversity environments using environmental DNA (eDNA): A test with Guianese freshwater fishes

“…The discrepancies between the local fish assemblage results of eDNA metabarcoding and traditional methods in Guianese stream and river sites might be partially explained by the incompleteness of the fish inventories created using traditional methods. Indeed, gill nets are known to be species selective and investigate the fish in a limited range of habitats (Murphy & Willis, 1996;Mojica, Lob on-Cervi a, & Castellanos, 2014). Similarly, rotenone samples investigate fauna from restricted reaches within streams that do not encompass all available habitats (Allard et al, 2016).…”

“…Our eDNA inventories are nevertheless incomplete, as a substantial part of the fauna captured using traditional methods was not detected using metabarcoding (Table 3). This might be due to imperfect detection (Mojica et al, 2014;Willoughby, Wijayawardena, Sundaram, Swihart, & DeWoody, 2016) or the erroneous attribution of reads to species. The incompleteness of the reference database (~25% of the species caught are not in the reference database, representing 24.31 AE 7.23% of the species at each site) might, for instance, explain the grouping of some reads in higher taxonomic units (genera or families).…”

Spatial and temporal distribution of Gymnorhamphichthys rondoni (Gymnotiformes: Rhamphichthyidae) in a long-term study of an Amazonian terra firme stream, Leticia - Colombia

“…This stream has a sandy bottom and is found in forest with a dense canopy. The area has moderate to low human intervention (Mojica et al, 2014).…”

“…The sampling site is 91 m in length. The fish community at this site was previously characterized in a long-term study (Mojica et al, 2014). The water system study depends highly on regional and local precipitation with fluctuating water level (0.4-1.9 m), associated with sporadic local precipitation that occurs mostly from November to May (monthly mean 350 mm) followed by a drier season from June to October (monthly mean 220 mm).…”

“…During the course of the year, water conductivity decreases as the average water level rises during the rainy season (Mojica et al, 2009). Oligotrophic and shallow terra firme streams in the Amazon basin contain high concentrations of humic and fulvic acids, low salt concentrations, and consequently exhibit both low pH and low electrical conductivity (Lobón-Cerviá et al, 2012;Mojica et al, 2014).…”