A near-natural experiment on factors influencing larval drift in Salamandra salamandra

Abstract

The larval stage of the European fire salamander (Salamandra salamandra) inhabits both lentic and lotic habitats. In the latter, they are constantly exposed to unidirectional water flow, which has been shown to cause downstream drift in a variety of taxa. In this study, a closed artificial creek, which allowed us to keep the water flow constant over time and, at the same time, to simulates with predefined water quantities and durations, was used to examine the individual movement patterns of marked larval fire salamanders exposed to unidirectional flow. Movements were tracked by marking the larvae with VIAlpha tags individually and by using downstream and upstream traps. Most individuals showed stationarity, while downstream drift dominated the overall movement pattern. Upstream movements were rare and occurred only on small distances of about 30 cm; downstream drift distances exceeded 10 m (until next downstream trap). The simulated flood events increased drift rates significantly, even several days after the flood simulation experiments. Drift probability increased with decreasing body size and decreasing nutritional status. Our results support the production hypothesis as an explanation for the movements of European fire salamander larvae within creeks.

Phenotype‐dependent downstream dispersal under ordinary flow conditions in juvenile white‐spotted char

“…Juveniles in the swimming group moved downstream from the initial release section more frequently than those in the SH group. This result is consistent with the general understanding of displacement in other flowsensitive species, such as larval salamanders (Schafft et al, 2022), aquatic invertebrates (Brittain & Eikeland, 1988;Naman et al, 2016), and small fishes (Lechner et al, 2016), where active individuals are more likely to encounter fast currents and thus are at higher risk of downstream displacement. The occurrence of downstream dispersal, on the other hand, could also have been affected by competitive interactions among juveniles because all fish were initially released into the single upstream section of the experimental channel, where the high density of juveniles may have fostered competition.…”

“…Juveniles in the swimming group moved downstream from the initial release section more frequently than those in the SH group. This result is consistent with the general understanding of displacement in other flow‐sensitive species, such as larval salamanders (Schafft et al, 2022), aquatic invertebrates (Brittain & Eikeland, 1988; Naman et al, 2016), and small fishes (Lechner et al, 2016), where active individuals are more likely to encounter fast currents and thus are at higher risk of downstream displacement.…”

“…Metabolic rates and boldness are associated with dispersal tendency in the round goby Neogobius melanostomus (Myles‐Gonzalez et al, 2015) and the brown trout Salmo trutta (Jones et al, 2021). Individuals with poor nutritional status tend to disperse downstream in the larval European fire salamander Salamandra salamandra (Schafft et al, 2022), and bold dunnock Prunella modularis with short flight initiation distances disperse into urban habitats, whereas shy individuals remain in rural habitats (Holtmann et al, 2017).…”

“…The occurrence of phenotype‐dependent downstream dispersal is well documented for dispersal caused by pulse flooding events, which cause strong flows that greatly exceed the coping capacity of the organisms (e.g., Blondel et al, 2020; Chapman & Kramer, 1991; Clark & Kershner, 2011; Meffe, 1984; Parkyn & Collier, 2004; Schafft et al, 2022; Yamada & Wada, 2021). However, phenotype‐dependent downstream dispersal can occur even in constant flows under non‐flooding conditions that organisms can potentially cope with (i.e., “ordinary” flows) (Bolnick et al, 2009; Jiang et al, 2015; Petranka et al, 1987; Thiesmeier & Schuhmacher, 1990).…”

Larval development and habitat usage of stream-breeding Fire salamanders in an urban environment

“…Small urodela larvae are more prone to drift (Bruce 1985), while upand downstream movements of various distances and with different water velocities have been documented for several species (Johnson & Wallace 2005, Lowe 2008, Cecala et al 2009. In a near-natural experiment, Schafft et al (2022) found that upstream movements of fire salamander larvae did not exceed more than 30 cm.…”