Quantifying Consumption of Native Fishes by Nonnative Channel Catfish in a Desert River

Abstract

The establishment of nonnative predators can have devastating consequences for native fish communities, but predation rates are often difficult to quantify due to spatial and temporal variation in predator foraging behavior. Predation by Channel Catfish Ictalurus punctatus throughout the Colorado River basin potentially threatens the recovery of native fishes. Because Channel Catfish are highly opportunistic feeders, an understanding of how piscivory by this species impacts prey populations should help to guide management in invaded systems. We used laboratory observations to model temperature‐dependent stomach evacuation rates and combined those estimates with field‐collected diet data to derive annual consumption across a 152‐km reach of the San Juan River (New Mexico, Colorado, and Utah). In the field, stomach fullness increased with water temperature while the probability of observing fish prey in the diet increased with TL of Channel Catfish and water turbidity. Based on estimates of daily ration, diet composition, and Channel Catfish population demographics, we estimated the San Juan River population’s fish consumption to be 4.9 kg·ha−1·year−1 (95% CI = 4.0–6.1 kg·ha−1·year−1) in 2018 and 2.3 kg·ha−1·year−1 (95% CI = 1.8–2.8 kg·ha−1·year−1) in 2019. Native fishes accounted for 54% of the fish biomass consumed, which included two incidents of endangered Colorado Pikeminnow Ptychocheilus lucius consumption. Although these estimates should help managers to assess the predatory threat of Channel Catfish, additional information, such as the efficacy of nonnative control and prey population compensatory responses, will likely be necessary to develop robust management strategies aimed at reducing the predatory impacts of this nonnative species on native fish assemblages.

Failure to achieve recommended environmental flows coincides with declining fish populations: Long‐term trends in regulated and unregulated rivers

“…This result could represent density‐dependent population regulation, in part via cannibalism (e.g., Lobón‐Cerviá, 2014). For instance, 50% of the fish prey identified in diets of adult channel catfish from the San Juan River were other channel catfish (Hedden et al, 2020). This result could also reflect a compensatory recruitment response to removal of adult channel catfish on the San Juan River, whereby removal of adults reduces predation pressure or frees up resources for juvenile fish (Pennock et al, 2018).…”

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

“…In contrast, P. lucius , a presumed piscivore 72 , exhibited a relatively small probability of overlap with other species, but this was dependent on the habitat. Some nonnative species, such as I. punctatus , are hypothesized to limit populations of native fish in the Colorado River basin through predation 73 , 74 . Our results suggest relatively little overlap between P. lucius , the species with the highest δ 15 N in the river upstream and I. punctatus , and supports other observations of limited piscivory by I. punctatus in the San Juan River 74 .…”

“…Some nonnative species, such as I. punctatus , are hypothesized to limit populations of native fish in the Colorado River basin through predation 73 , 74 . Our results suggest relatively little overlap between P. lucius , the species with the highest δ 15 N in the river upstream and I. punctatus , and supports other observations of limited piscivory by I. punctatus in the San Juan River 74 . Although we observed more overlap among species in the two habitats downstream of the waterfall, we do not expect competition is a strong driver of assemblage dynamics as river-reservoir inflows are not likely resource-limited 26 , 75 , 76 .…”

Catfish 2020, A Clear Vision of the Future

“…This pattern in nonnative catfish populations is seen with Blue Catfish I. furcatus (Fabrizio et al 2021;Hilling et al 2021;Nepal and Fabrizio 2021; all this special issue), bullheads Ameiurus spp. (Barabe 2021;Sikora et al 2021; both this special issue), Channel Catfish I. punctatus (Pennock et al 2018;Hedden et al 2021, this special issue), and Flathead Catfish Pylodictis olivaris (Hedden et al 2016;Massie et al 2018;Schmitt et al 2019;Smith et al 2021, this special issue), which was summarized by Montague and Shoup (2021, this special issue). The extent, ecology, and impacts of nonnative, invasive catfish populations are becoming better understood over time, and Fabrizio et al ( 2021) described the conflicts involved in managing invasive catfish.…”

“…2018; Hedden et al. 2021, this special issue), and Flathead Catfish Pylodictis olivaris (Hedden et al. 2016; Massie et al.…”