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,rl :1 (t r.:.I.. r r I II II JI ;1 tl !I...-- J ":1 \1 ~,~ ,I 'I LI ,I I 2. Telemetry Studies The movement and behavior of razorback and flannelmouth suckers were studied using telemetry equipment. The objective was to determine where resident fish were spawning and examine post-stocking related stress. Resident Fish Tests Twenty resident (each) razorback sucker and flannelmouth sucker were captured and implanted with radio transmitters at either Big Bend State Park, Nevada, or Park Moabi, California. Fish were implanted with transmitters in hopes they would lead us to spawning sites. Eight boat and three helicopter surveys searched for the fish between Davis Dam and the upper portion of Lake Havasu. Unfortunately, we soon lost contact with the fish. We believe the reason contact was lost stemmed from the equipments limited range and depth. Either the fish moved outside the study area or had moved to a depth (>4 m) where the transmitters could not be detected. Eighteen-month radio (40 MHZ) transmitters with self-contained antennae were selected because of the long-term duration of the study. We believed this transmitter type would provide information over two spawning seasons. Lost contact of the fish is perplexing. Even with mortality, signals should have been detected unless fish moved to depths >4 m, which would dampen signal transmission. The transmitters we used had internal antenna that unfortunately produce a signal that is supposedly 25% weaker than transmitters with external antennae. The internal antenna was selected since it did not have to tail out of an abdominal wound. Fish implanted with external antennae are more prone to abdominal infections and mortality. We suspect poor signal performance and possibly fish moving toward deeper habitats limited detection. The Importance of Physiology and Behavior in Survival The use of standard hatchery techniques in the production and stocking of endangered or economically important fishery stocks has drawn considerable attention lately (Brown and Day, 2002). Survival related issues have persisted in the reintroduction of native fish in the Colorado River for over two decades (Minckley and Deacon, 1991; Mueller and Marsh, 2002). Past efforts to stock razorback suckers have been plagued by predation and what appears to be poor conditioning that results in chronic fatigue which may lead to mortality (Marsh and Brooks, 1989; Burdick and Bonar, 1997; Mueller and Foster, 1999). Several researchers have questioned the manner in which hatchery fish are raised and stocked but few studies have examined these issues (Marsh and Brooks, 1989; Burdick and Bonar, 1996; Mueller and Foster, 1999). We encountered further supporting evidence. Four juvenile razorback suckers were captured downstream of Davis Dam that were originally stocked in Lake Mohave. The only way those fish could have reached their collections site was to have traveled through Davis Dam and its power plant (i.e., successful turbine passage). The likelihood of 25-30 cm fish successfully surviving passage through turbines has been shown to be remarkably small (<.01) (Nibling and Liston, 1992). For us to encounter that many suggests substantial numbers of juvenile suckers were entrained and the vast majority killed. This may partially explain the relatively low survival rates (<12%) being experienced in Lake Mohave (Marsh oral communication). We tested the post-stocking dispersal of razorback suckers, feeling that downstream drift could be a symptom of chronic stress, especially when fish are being released in flowing habitats. Hatchery protocols that have worked effectively for recreational species appear to be far less effective for some native fishes. 20