Distribution, migratory behavior, and habitat use of razorback sucker (Xyrauchen texanus) in Lake Mohave, Arizona-Nevada

Abstract

captive-reared fish from previous stockings (Marsh and Minckley 1989a). The Native Fish Work Group formed as a coalition of concerned state and federal agencies for the purpose of stocking 50,000, juvenile razorback suckers to replace the old population that was dying out in Lake Mohave (Mueller 1995). Stocked fish are monitored to determine the appropriate sizes needed to ensure adequate survival. Preliminary information suggests that approximately 57% over 20 cm have survived (Marsh 1997). Predation is believed to be a major factor that limits recruitment from natural spawning. Survival is size dependent but other factors, such as time and location of stocking, cove availability, predator densities, and behavioral traits that could also impact survival. The purpose of this study was to gain a better understanding of the migratory behavior and habitat used by juvenile and adult razorback suckers in a reservoir environment. As adults become rare and more difficult to capture, information regarding their movements and habitat use will become more important in monitoring populations. In addition, understanding habitat use and behavior of juveniles will allow assessment of predation, stocking protocols, and factors that can enhance survival and recovery. METHODS Study Specimens Adults-Adults were trammel netted at Yuma and Tequila coves (Figure 1, RK 34& 39) during November 6-7, 1994. Five males and five females were selected and held at each site for surgery the following morning. The Yuma Cove fish were surgically implanted and released on November 7th and the Tequila Cove fish were implanted and released on November 8th. Adults averaged 609 mm (555-680 mm) in total length and 2.78 kilograms (1.75-4.21 kg). Individual data pertaining to length, weight, PIT tag numbers, sonic transmitter code, release location, and distances moved are summarized in Appendix A. Juveniles Twenty five juvenile suckers were taken from grow-out ponds and held in holding facilities at the Bureau of Reclamation laboratories in Boulder City, Nevada. The fish were later transported by truck and by boat on November 22, 1994. Fish averaged 338 mm (315 to 392 mm) and 369 grams (296-598 g). The juveniles were released in groups of four fish at: Red Light Cove (RK 10), Dandy Cove (RK 17), Owl Point (RK 45), Double Neck Cove (RK 71), and Cross Current Rapids (RK 92). Pertinent information is summarized in Appendix A. Telemetry Equipment We determined a 30+-cm sucker was capable of carrying a 6 gram, 16 X 5 5-mm sonic transmitter (Sonotronics model CTT-83-2) (Knowles 1994

Razorback sucker transbasin movement through Lake Powell, Utah

“…Efforts to restore the gene pool of fishes in Lake Mohave by capturing and rearing larval razorback sucker have identified predation by nonnative fishes as a major cause of mortality of young fish (Marsh 1987(Marsh , 1994Mueller 1995;Mueller et al 1998). These studies have found increased survival and growth of razorback sucker and bonytail under predator-free environments .…”

“…What happens to them is unknown; they may be dispersing to deeper water, but the near absence of juveniles suggests mortality at the larval stage, probably as a result of predation (Marsh and Langhorst 1988;Horn 1996). Five tagged juveniles in Lake Mohave moved throughout the pelagic zones for the first week after release but then tended to occupy vegetated areas near the shore (Mueller et al 1998).…”

“…In both lotic and lentic environments, adults have been documented to travel to aggregate near spawning sites Modde and Irving 1998;Mueller et al 2000). Historic reports of large numbers of adult razorback sucker amassed in a single location are attributable to spawning runs and aggregations (Jordan 1891; Hubbs and Miller 1953;Sigler and Miller 1963;.…”

Genetic structure within and among populations of the endangered razorback sucker (Xyrauchen texanus) as determined by analysis of microsatellites

“…Females can be extremely fecund, with some of the larger individuals capable of producing more than 100,000 ova per year. Telemetry studies have shown that they are capable of considerable movement, including trips to multiple spawning areas within a season (Tyus and Karp 1990;Mueller et al 2000;Karam et al 2008).…”

Sperm quality assessments for endangered razorback suckers Xyrauchen texanus

“…This riverine catostomid in the order Cypriniformes was formerly abundant throughout the entire lower Colorado River drainage (Minckley et al 1991), but the current range for the residual wild populations is primarily limited to Lake Mead, Lake Mohave (Mueller et al 2000), and the middle Green River drainage (Modde et al 1996, Cooke et al 2005. Although the low levels of recruitment (replacement with younger individuals) have been directly linked to competition with, and predation by, non-native fish introduced for sportfishing (Minckley et al 1991), the reduced availability of floodplain habitat (Modde et al 1996) and the continued declines of flows into the Colorado River (Barnett & Pierce 2008) will likely exacerbate the predicted losses of remaining sustainable populations of razorback suckers.…”