Razorback Sucker Movement Strategies across a River–Reservoir Habitat Complex

Abstract

Razorback Sucker Xyrauchen texanus occur in reservoir and riverine habitats in the Colorado River basin, with some individuals aggregating at river–reservoir inflows. To assess use of inflow areas and potential environmental correlates with fish movement among reservoir and river habitats, we used a passive receiver array to monitor location and movements (n = 69) and depth (n = 19) of acoustic‐ and PIT‐tagged fish in Lake Powell from April 2018 to March 2019. Acoustic receivers were deployed along 18 km of the San Juan River–Lake Powell inflow area, and a PIT tag antenna was deployed below a waterfall that impedes all upstream movement approximately 30 km upstream of the inflow area. Fish were detected moving between the inflow area and the river in all seasons except winter. Fifty‐eight percent of fish moved from the reservoir and were detected upstream at the waterfall, while 42% of fish appeared to remain within the reservoir. These reservoir‐resident fish moved long distances (hundreds of kilometers) but had relatively small linear home ranges (<18 km). On average, fish moved farthest and home range size was largest from April to September, and seasonal differences corresponded with differences in the number of fish detected. River discharge was relatively constant, and monthly distance moved was positively correlated with monthly river temperature, suggesting temperature alone might cue movements. Fish were detected at depths of 5.7 m but generally remained in shallow water (<2 m). Causal mechanisms that drive habitat use by adult fish are unclear but likely involve intraspecific differences in response to resource needs. We hypothesize that reservoirs provide warmer temperatures for longer periods of the year relative to regulated rivers, which might benefit warmwater fishes. Understanding the importance of movement among river and reservoir habitats might further conservation efforts by encouraging inclusion of reservoir habitats in management plans.

Trophic niches of native and nonnative fishes along a river-reservoir continuum

“…Some fish species could be partitioning habitat and garnering energy from more littoral or pelagic resources in the reservoir 42 . For instance, D. cepedianum and X. texanus might forage more in the littoral zone or shallower in the water column where food resources are less depleted 84 – 86 , which matches patterns observed in other food web and habitat use studies from Lake Powell 87 , 88 . The δ 13 C signature of X. texanus captured in the river downstream of the waterfall align more with that from the reservoir than the river upstream, which was not surprising since this species moves in the river for only a few weeks or months (M. Bogaard, unpublished data), spending most of their time in the reservoir 87 .…”

The North American Freshwater Migratory Fish Database (NAFMFD): Characterizing the migratory life histories of freshwater fishes of Canada, the United States and Mexico

“…Huckins et al, 2008). Recent research is finding that populations with migratory and non‐migratory individuals are more prevalent than previously thought (Dzul et al, 2021; Pennock, McKinstry, & Gido, 2020). For example, individual Central Stonerollers ( Campostoma anomalum ) can migrate up to 1 km between pools and other riverine habitats while other individual C. anomalum remain in pools for their entire life cycles (Pennock et al, 2018).…”

Translocation in a fragmented river provides demographic benefits for imperiled fishes

“…For instance, in previous research, a fish translocated in 2016 and recaptured during the next translocation period in 2017 would have been counted as returning downstream within a year (Pennock, McKinstry, Cathcart, et al, 2020), but our current model is structured such that these individuals would not contribute to the 2016 downstream transition probability because the next translocation period occurs in a different year. Regardless, there is consistent mass movement back downstream following translocation for razorback sucker, and this is likely driven by the availability and proximity of critical habitats and resources in addition to diverse movement strategies (e.g., Pennock, McKinstry, & Gido, 2020). Downstream transition probabilities for non‐translocated fishes were low (all species <0.03), and because translocated fishes were released within 4 km of the waterfall, these individuals were more likely to move back downstream simply by random chance.…”

“…Additionally, we estimated survival and transition probabilities of translocated and non‐translocated fishes with a spatially explicit multistate mark–recapture model to assess whether translocation influenced the survival of native fishes and estimated their probability of emigrating downstream of the Piute Farms Waterfall relative to non‐translocated fishes upstream. Razorback sucker use river–reservoir inflow areas in several places throughout the Colorado River basin including the San Juan River–Lake Powell inflow area (e.g., Albrecht et al, 2018; Pennock, McKinstry, Cathcart, et al, 2020; Pennock, McKinstry, & Gido, 2020), and previous research has identified many translocated fish moving back downstream to the reservoir following translocation or fish residing completely within the reservoir in some years (Bogaard, 2021; Pennock, McKinstry, Cathcart, et al, 2020; Pennock, McKinstry, & Gido, 2020). Because razorback sucker are more apt to use reservoirs than other native fishes (e.g., Albrecht et al, 2010, 2018; Pennock et al, 2023), we expected survival to be similar between translocated and non‐translocated individuals and transition probabilities back below the waterfall to be higher for razorback sucker compared with the other native fishes.…”