Exercise conditioning of pond-reared razorback suckers (Xyrauchen texanus) decreases rate of downstream movement upon release into a stream environment.

Authors: Luke A. Avery, David L. Ward, Jane C. Marks

Year: 2009 (xli)

Abstract

This study was conducted to determine if exercise conditioning could decrease downstream movement of pond-reared razorback suckers, Xyrauchen texanus , upon release into a stream environment. The razorback sucker is a Southwestern fish species that is federally listed as endangered. Despite efforts at recovery, populations continue to decline. The current recovery technique is augmentation stocking using fish that have been reared in off-channel habitats. Once the fish reach 300-500mm TL they are released into stream habitats where large downstream movement has been observed (Mueller et. al, 2003, N. Amer. J. of Fish. Sci. 23:270-275). We conducted an experiment to determine if this downstream movement could be reduced. Two groups of PIT (Passive Integrated Transponder) tagged razorback suckers, one that had been exercise conditioned and one that had not, were released into Fossil Creek, AZ. Prior to release, a subsample from each treatment group was tested for their ability to maintain a position in the water column using a flow-tube with variable water velocities. This test was conducted to determine if the exercise treatment was having an effect that may not have been detected in the field. Razorback suckers that had been exercise conditioned were able to maintain a position in the water column longer and at higher water velocities than non-exercised fish. The intended method of field data collection via a PIT antenna and remote communication station failed, though useful remote communications technology was developed. The released razorback suckers were heavily preyed upon by river otters (Lutra canadensis). The implanted PIT tags were frequently ingested along with the fish and passed by the otters and retained in their scat. Recovery of these PIT tags enabled distributional analysis. Razorback suckers that had been exercise conditioned moved downstream at a slower rate than the non-exercised razorbacks.