Fish assemblages and their ecological traits along an elevational gradient in the Río Pacuare, Costa Rica

Abstract

Between May 2004 and May 2005, we sampled fish in 19 sites, grouped in four elevations, ranging from the river mouth to 650 m.a.s.l. in the Río Pacuare, Caribbean versant of Costa Rica. Changes in the distribution and composition of the fish fauna, as well as patterns of alpha and beta diversity along an elevational gradient were assessed. Additional analyses of habitat preferences, trophic guilds, functional groups and general ecology for the most abundant species are included. All fish captured were classified into 22 families, 43 genera and 53 species. The most abundant family was Characidae, followed by Gobiidae, Mugilidae, Poeciliidae and Heptateridae, which together comprise 87.9 % of all sampled individuals. Elevation shows an inverse effect on species diversity, we observed a monotonic decrease in species richness with increasing elevation (p < 0.05), as reported in other tropical rivers. According to our results, in the Río Pacuare the total fish fauna diversity is found within the first 500 m.a.s.l. Species turnover increases with elevation, while nestedness decreases. Turnover was dominated by the loss of species rather than gain; the higher species loss was registered between the river mouth and the lower river reach (< 100 m.a.s.l.). Seven species can be classified as typical or core species (Astyanax aeneus, Sicydium altum, Agonostomus monticola, Poecilia gillii, Brycon costaricensis, Rhamdia laticauda and Joturus pichardi) along the elevation gradient. The habitat availability and the integration of ecomorphological, feeding and reproductive traits help to explain better the elevation distribution of the complete set of species observed. Although it is possible to identify groups of species characteristic of each reach of river, this does not mean that they are isolated from each other. Natural drift and movement along the river of some species during their life cycle, especially S. altum, A. monticola and J. pichardi, are key processes linking the whole watershed. The present study constitutes a first step in documenting and understanding the distribution and composition of fish assemblages in a watershed that is relatively intact and well-conserved in the Caribbean versant of Costa Rica.

Diet and reproduction of the fish Joturus pichardi (Mugiliformes: Mugilidae) in the Pacuare River basin, Costa Rica

“…The results obtained describe some important aspects of diet and reproduction of J. pichardi. Our habitat structure data coincide with other authors about the preference for sites with higher water velocity, high values of dissolved oxygen and are related to sites with greater forest cover (Bussing & López, 1977;Cruz, 1987;Bussing, 2002;Eslava & Díaz, 2011;Lorion et al, 2011;Barboza & Villalobos, 2018). This relationship could condition the presence of this species within the altitudinal gradient of the river, so a change within the flow or drastic modifications of land use can generate a negative effect within the populations.…”

“…Study area and sampling sites: The Pacuare River basin has an area of 914km 2 with a length of 134,39km and an average rainfall of 2 000 to 5 000mmy -1 (Barboza & Villalobos, 2018). The basin has a maximum elevation of approximately 3 000masl.…”

“…In the Central American region, migratory freshwater fishes are known mainly within the families Mugilidae, Eleotridae and Gobiidae (Matamoros et al, 2009;Lorion, Kennedy, & Braatne, 2011;Angulo et al, 2013;McMahan et al, 2013), and there are some efforts to understand the migratory behavior, aspects of distribution, diet and reproduction of some them, mainly species as Joturus pichardi and Dajaus monticola (Mugilidae) and some species of the genus Sicydium (Gobiidae) (Bussing & López, 1977;Cruz, 1987;Cruz, 1989;Bussing, 2002;Lyons, 2005;Ribeiro & Villalobos, 2010;Eslava & Díaz, 2011;Lorion et al, 2011;Barboza & Villalobos, 2018;González-Murcia & Álvarez, 2018), however, there are still gaps in information. In addition to this, there are currently conservation difficulties for this group due to development of hydroelectric plants (Anderson, Freeman, & Pringle, 2006;Liermann, Nilsson, Robertson, & Ng, 2012), fragmentation and alteration of habitat, and different environmental problems that threatens the conservation of freshwater ecosystems and fish populations (McDowall, 1992(McDowall, , 1999Hardesty-Moore et al, 2018).…”

“…In Costa Rica, despite the fact that J. pichardi is a species of great local interest and that has interesting migratory patterns, there are very few studies that address the current status of the populations (e.g. Bussing & López, 1977;Bussing, 2002;Lorion et al, 2011;Barboza & Villalobos, 2018).…”

Morphometry and burst swimming in six continental fish species from Costa Rica

“…To sort out the position in the water column (PWC) of each specie, we used the information in Chapman, Kramer and Chapman (1991), Wisenden (1994), Trujillo-Jiménez (1998), Tabash and Guadamuz (2000), Barboza and Villalobos (2018) and Djumanto, Ustadi, Rustadi and Triyatmo (2018).…”