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<br />positioned on the bow. The boat moved downstream under power at a constant speed <br />that matched water velocity to maximize netting efficiency. Only shoreline or <br />associated habitats (backwaters, eddies, tributary mouths) were sampled. Crews <br />electrofished one side of the river until the entire reach was sampled and then returned <br />upstream and sampled the other side either on the same or next day. If an endangered <br />fish was captured, sampling was stopped until the requisite data were recorded and the <br />fish released. <br />After each Colorado pikeminnow capture, the sampling crew reported the <br />proximity of the fish to the nearest electrode (ft, later converted to m) and fish behavior <br />(physiological state) when netted. Physiological states at capture included swimming, <br />stunned, or tetany and represented the fish's ultimate response to the electrical field. <br />Fish that were swimming when captured were generally swimming toward an electrode <br />in electrotaxis. Stunned fish had lost equilibrium and stopped swimming and were in a <br />state of narcosis or the beginning stages of tetany. Most stunned fish recovered <br />immediately when removed from the electrical field. Fish captured in a tetanized state <br />were immobilized and rigid due to sustained muscle contraction and often required <br />longer to regain orientation and recover than stunned fish. The sampling crew was also <br />queried about control-unit settings such as voltage, amperes, and pulse width. <br />At capture fish were placed in the boat live-well containing fresh river water, <br />transported to shore, and then transferred to a 3D-liter, plastic holding tank (food cooler) <br />containing river water treated with 5-1 D g/L salt (NaCI) solution to help the fish maintain <br />osmotic balance. Prior to the x-ray procedure, fish were sedated in another cooler with <br /> <br />3 <br />