Author(s): Rafael Tinoco; Vindhyawasini Prasad

Linked Author(s): Rafael Tinoco

Keywords: Grass carp; Invasive fish; Turbulence; Floating vegetation

Abstract: Grass carp (Ctenopharyngodon idella) is one of four invasive carp species in North America (grass carp, black carp, silver carp, and bighead carp). Once they establish in a water body, they outcompete endemic species and can permanently change the local ecosystem. Efforts to mitigate their spread have had various levels of success. While most strategies focused on removal of adult specimens, recent studies have focused on understanding the transport of early life stages on streams, identifying their response to turbulent conditions (Tinoco et al. 2022) and potential flow-based capture strategies (Prasad et al. 2024, 2025). We conducted a series of laboratory experiments with live grass carp larvae to identify potential preferential pathways and capture areas through a channel with a patch of floating vegetation. We tested different submergence ratios of a dense patch of flexible vegetation over a range of subcritical turbulent flows. Particle image velocimetry was used to characterize the velocity field through and below the patch. The study revealed a clear active response of grass carp larvae to vegetation -generated turbulence and coherent flow structures. Comparing the flow turbulence statistics to the spatial distribution of larvae, we identified that larvae not only looked for areas of low velocity, but rather avoided regions of high shear, and stayed away from areas where turbulent eddies matched the size of larvae. The results provide useful guidelines for the design of monitoring, capturing, and management strategies of fish larvae in vegetated streams.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.311

Year: 2026