Effects of intraperitoneally implanted radio transmitters on the swimming performance and physiology of Pacific lamprey

Information on movement patterns and behaviors of Pacific lampreys Lampetra tridentata at Columbia River hydroelectric projects is needed to determine effects of the dams on survival. Radiotelemetry provides a good method for gaining knowledge about Pacific lamprey behavior at the dams; however, one of the assumptions of a radiotelemetry experiment is that tagged individuals are representative of untagged individuals. Therefore, we undertook an assessment of the swimming performance and physiological effects of surgical implantation of radio transmitters into the peritoneal cavities of Pacific lamprey. We measured concentrations of plasma glucose, ventilation rate, and swimming performance at short-term and long-term intervals following the surgical implantation of radio transmitters in Pacific lamprey. We found no short-term difference in glucose levels between tagged (3.4-g tags) and control lampreys, suggesting tagging is no more stressful than handling. Plasma levels of glucose in Pacific lampreys implanted with 7.4-g transmitters were greater at 3 and 24 h postsurgery compared with controls; however, these differences disappeared at 96 h. Ventilation rates of tagged (7.4 g) and control lampreys did not differ at 1, 24, and 168 h after surgeries. Swimming performance of Pacific lampreys implanted with 7.4-g transmitters was impaired immediately after surgery; however, swimming was not compromised at 1 and 7 d after surgery. In the long term (i.e., 4 months postimplantation), plasma glucose levels in lampreys implanted with 3.4-g transmitters did not differ from control or sham lampreys, whereas those implanted with 10.0 g transmitters had higher plasma glucose than intact controls. Adult lampreys implanted with 7.4-g transmitters remained statistically indistinct from controls at 30, 60, 90, and 180 d after surgery. Of the control and 7.4-g tagged lampreys, 22% matured and developed secondary sexual characteristics with loose eggs or flowing milt by the end of March. We found 100% survival rate with our tagged fish in all experiments. These results indicate that radio tags weighing 7.4 g or less that are surgically implanted in adult Pacific lamprey can meet the core assumption of radiotelemetry, provided precautions are taken to ensure adequate time for recovery from surgery.