Habitat and resource use by larval and juvenile fishes in an arid‐land river (Rio Grande, New Mexico)

Abstract

1. Studies of mesic temperate and tropical rivers suggest an important role for floodplain habitats as nursery areas for larval and juvenile fishes. In arid-land rivers the extent and duration of flooding is diminished and habitats and resources used by larval fishes are poorly known. Our study documented habitat and resource use of larval fishes in the Rio Grande, New Mexico, an arid-land river. 2. Spatial and temporal distribution of larval and juvenile fishes and their inferred microhabitat preferences were studied during spring, summer and autumn, 2003. Stable carbon ( 13 C : 12 C) and nitrogen ( 15 N : 14 N) isotope ratios were measured to identify nutrient sources and characterise trophic positions of young-of-year fishes in this system. 3. Some fishes recruited during high flows (in spring), whereas others recruited during low-flow periods in late summer. Regardless of the timing of reproduction, microhabitats with lower current velocity and higher temperature appeared to serve as vital nursery grounds for Rio Grande fishes. Ephemeral backwaters and disconnected side channels held the highest abundance and diversity of larvae and juveniles. 4. Stable isotope analyses revealed that fish larvae obtained carbon predominately from algal production in early summer, but used organic carbon derived from emergent macrophytes as river discharge decreased in mid-summer. This shift may have been facilitated by microinvertebrate prey that grazed down edible algae and then switched to macrophytes in mid-summer. Nitrogen isotope ratios did not differ among species or early life stages, suggesting that larval and juvenile fishes use similar food resources, especially when restricted to isolated pools in summer.

Ontogenetic changes in the food items assimilated byPlagioscion squamosissimus(Perciformes: Sciaenidae) andHypophthalmus edentatus(Siluriformes: Pimelodidae)

“…The specimens were rinsed with distilled water to remove excess alcohol and dried at 60 C. The same samples used here had their isotopic results corrected by subtracting 0.5%. This correction value for 15 N was obtained by Manetta et al (in press) for the same species in the adult phase and recorded by Vander-Zanden et al (2003) and Pease et al (2006) for adults and larval marine fishes, respectively. Afterward, the samples macerated until a fine powder was obtained.…”

Population structure, reproductive biology and feeding of Astyanax fasciatus (Cuvier, 1819) in an Upper Paraná River tributary, Misiones, Argentina

“…Other factors that could influence the gonad maturation and spawning of other species are abiotic factors such as variations in the hydrometric level, rains, high temperatures and the photoperiod (Azevedo, 1972;Basile-Martins et al, 1975;Colares de Melo, 1989;Winemiller et al, 2000;Zeug and Winemiller, 2007). According to Pease et al (2006), the flooding period and the low speed in flooding habitats are important factors for the reproduction and development of larvae.…”

Variability in the trophic position of larval fishes in theupper Paraná floodplain based on δ15N

“…Based on a study by Manetta and Benedito (in press) that used the same species in the adult phase, the isotopic results for these samples were corrected by subtracting 0.5 . This correction factor has also been used by Vander Zanden et al (2000) and Pease et al (2006) for several species of fishes in the adult and larval stages, respectively.…”