Influence of habitat dynamics on the distribution and abundance of the federally threatened Santa Ana Sucker, Catostomus santaanae, in the Santa Ana River

Abstract

Habitat degradation affects native stream fish populations worldwide.

Dam effects on bedload transport on the upper Santa Ana River, California, and implications for native fish habitat

“…The wastewater discharges have established a channel of about 10‐m width, which is inset within the much larger flood control channel (about 250‐m width). This inset channel supports the only remaining population within the watershed of the Santa Ana sucker (Thompson, Baskin, Swift, Haglund, & Nagel, ). An important aspect of the inset channel habitat is the presence of coarse particles (gravel and cobble), which provide the substrate for the sucker food base of diatoms and algae (Burton, Brown, & Belitz, ; Thompson et al, ).…”

Loss of dendritic connectivity in southern California's urban riverscape facilitates decline of an endemic freshwater fish

“…The widespread nature of remaining bottleneck examples points to interfacing contemporary and historical factors as drivers of population decline in C. santaanae , including prolonged droughts punctuated by major floods (Dettinger, , ), changes in stream morphology and connectivity over the past century (Thompson et al., ; USFWS 2017), and in recent decades, increased incidence of catastrophic fires and associated debris flows (Moody, Shakesby, Robichaud, Cannon, & Martion, ; Steel, Safford, & Viers, ; Syphard et al., ; Westerling et al., ). Wholesale species decline may be progressing through a ratcheting effect (Birkeland, ), as reduced capacity to offset the genetic effects of bottleneck cycles is further compromised by the increasing severity of the environmental factors that create them, many of which are predicted to worsen with climate change (Dettinger, ; Seager et al., ; Westerling et al., ).…”

“…Spatial structure in this part of the range therefore appears to be modulated by two drift-related factorsa founder event in San Dimas Canyon has caused rapid divergence after translocation from the upper San Gabriel River, while at the same time, greater retention of shared F I G U R E 4 Results for the direct and logistic regression approaches to estimating the posterior probability of the different scenarios for each set of DIYABC analyses (a-d). The x-axis represents the number of simulated data sets closest to the observed data, and the y-axis denotes the median posterior probability for a given scenario (Dettinger, 2011(Dettinger, , 2013, changes in stream morphology and connectivity over the past century (Thompson et al, 2010;USFWS 2017), and in recent decades, increased incidence of catastrophic fires and associated debris flows (Moody, Shakesby, Robichaud, Cannon, & Martion, 2013;Steel, Safford, & Viers, 2015;Syphard et al, 2007;Westerling et al, 2006). Wholesale species decline may be progressing through a ratcheting effect (Birkeland, 2004), as reduced capacity to offset the genetic effects of bottleneck cycles is further compromised by the increasing severity of the environmental factors that create them, many of which are predicted to worsen with climate change (Dettinger, 2011;Seager et al, 2007;Westerling et al, 2006).…”

“…It exists in the three watersheds that drain into the Los Angeles Basin and a fourth that drains into the Ventura coastal plain (Figure ). Loss of an estimated 70%–80% of the historical range (Moyle, ; O'Brien, Hansen, & Stephens, ; Thompson, Baskin, Swift, Haglund, & Nagel, ) has disrupted fractal‐like connectivity between low‐order reaches in the mountains surrounding the greater Los Angeles area and high‐order reaches in alluvial basins to the west–southwest. Some populations survive in stream sections that are dependent on the effluent from wastewater treatment facilities, and a host of non‐native plant (e.g., Arundo donax and Compsopogon coeruleus ) and animal species (e.g., largemouth bass Micropterus salmoides , red shiner Cyprinella lutrensis and green sunfish Lepomis cyanellus ) pose threats to survival (Jenkins et al, ; Moyle, ; Swift, Haglund, Ruiz, & Fisher, ; USFWS, 2017).…”

Nutritional physiology of the Santa Ana sucker (Catostomus santaanae): A threatened freshwater fish endemic to Southern California

“…For an organism with federal protections, C. santaanae is understudied. For example, past reports of diet have been solely observational (Greenfield et al, 1970;Saiki et al, 2007;Thompson et al, 2010). Further, an understanding of C. santaanae resource use and food preference is important for managing its conservation in the light of its existence in degraded urban watersheds, such as the Santa Ana River, which can be subject to extreme flow manipulations and impacted habitat F I G U R E 1 Natural watersheds of Catostomus santaanae in southern California, USA.…”