Strategies to avoid the trap: stream fish use fine-scale hydrological cues to move between the stream channel and temporary pools

Abstract

For species living in highly variable environments, the ability to perceive and respond to environmental cues by moving into favorable habitats should convey evolutionary advantages. Here we examined the spatial dynamics of an Amazonian pencil fish species that shows seasonally varying use of stream channel and temporary pool habitats. We hypothesized that movement into the pools should be driven by cues that reflect availability of spawning sites, whereas movement out of the pools should be driven by cues that help avoid entrapment as water level declines. Survival, detection, and movement probabilities were estimated from capture histories of individuals recorded on 13 surveys along a hydrological cycle. Differences between habitats were small for detection probability and survival. Movement from stream to pools was greatest during bankfull overflow, whereas movement from pools to stream was related to rapid decline in pool area. Entry to pools during overflow may allow fish to choose favorable spawning sites while still permitting a swift return to the stream if conditions in pools deteriorate. The ability to interpret hydrological cues seems to allow pencil fish to cope with environmental uncertainty by timing its use of seasonally available spawning sites while avoiding entrapment in desiccating pools. © 2016, Springer International Publishing Switzerland.