Barriers Impede Upstream Spawning Migration of Flathead Chub

Abstract

Many native cyprinids are declining throughout the North American Great Plains. Some of these species require long reaches of contiguous, flowing riverine habitat for drifting eggs or larvae to develop, and their declining populations have been attributed to habitat fragmentation or barriers (e.g., dams, dewatered channels, and reservoirs) that restrict fish movement. Upstream dispersal is also needed to maintain populations of species with passively drifting eggs or larvae, and prior researchers have suggested that these fishes migrate upstream to spawn. To test this hypothesis, we conducted a mark-recapture study of Flathead Chub Platygobio gracilis within a 91-km reach of continuous riverine habitat in Fountain Creek, Colorado. We measured CPUE, spawning readiness (percent of Flathead Chub expressing milt), and fish movement relative to a channel-spanning dam. Multiple lines of evidence indicate that Flathead Chub migrate upstream to spawn during summer. The CPUE was much higher at the base of the dam than at downstream sites; the seasonal increases in CPUE at the dam closely tracked seasonal increases in spawning readiness, and marked fish moved upstream as far as 33 km during the spawning run. The upstream migration was effectively blocked by the dam. The CPUE of Flathead Chub was much lower upstream of the OHDD than at downstream sites, and <0.2% of fish marked at the dam were recaptured upstream. This study provides the first direct evidence of spawning migration for Flathead Chub and supports the general hypothesis that barriers limit adult dispersal of these and other plains fishes.

Historical data reveal fish assemblage shifts in an unregulated prairie river

“…These species' shared reproductive strategy enables reproduction in streams with high suspended sediments and unstable sand or silt substrates, and facilitates the repopulation of downstream habitats that may be fragmented by intermittency. However, localized extirpation of pelagic spawners has been seen in fragmented river segments due to instream migration barriers preventing the upstream movement of adults (Luttrell et al 1999, Walters et al 2014) and reduced downstream dispersion and recruitment of drifting eggs and larvae (Dudley and Platania 2007). The Powder River is undammed upstream v www.esajournals.org of its confluence with the Yellowstone River, but habitat fragmentation could still be occurring due to irrigation diversion structures which can act as barriers to upstream migration.…”

Fragmentation and dewatering transform Great Plains stream fish communities

“…point to previous examples of reestablishment or increased dispersal following barrier removal or mitigation as proof of concept that increasing connectivity benefits fishes known to respond negatively to fragmentation (Catalano et al 2007, Archdeacon and Remshardt 2012, Walters et al 2014). …”

Juvenile migration of the exclusively pelagic cyprinid, Gnathopogon caerulescens (Honmoroko) in Lake Biwa, Central Japan

“…Because migratory cyprinids rely on multiple habitats and open‐water passages to migration destinations, the conservation of the latter requires thoughtful consideration so as to enhance the likelihood of completion of all life‐history stages (Brönmark et al, ). Since habitat fragmentation and barriers that restrict fish movement may make migration the most vulnerable stage in the life cycle, conservation management proposals need to have considered migration of cyprinids (Smith, ; Lucas & Batley, ; Lucas & Frear, ; Walters et al, ).…”