Post-Release Survival and Behavior of Walleye Tagged with Internal Acoustic Transmitters: Do They Sink or Swim?

Coinciding with advances in acoustic telemetry technology, the studies focusing on the movement and behavior of wild fish have proliferated in recent years.  However, there has not been a concomitant increase in the understanding of how the tagging procedure (i.e., collection and surgical process) affects the organism, specifically as it relates to survival and behavior.  In 2013 we captured, implanted acoustic transmitters and released 165 walleye into a VEMCO Positioning System (VPS) acoustic array in the vicinity of a spawning shoal in the western basin of Lake Erie.  Based on the positions generated from the VPS array, swimming velocities were calculated to evaluate post-release survival and behavior for up to three days post-release.  Additionally, we used individual fish detection histories to evaluate post-release survival within three months of release.  Using this information we estimated that 77% of the walleye released survived at least three months.  Swimming activity was low immediately following release but increased as the time at liberty increased.  Thus, researchers should recognize that the tagging procedure may influence short-term behavior of the study fish and that some level of data censoring may be necessary to avoid arriving at erroneous conclusions.