Evaluating the viability of the use of two tag types on prespawn Arctic lamprey

Abstract

Arctic Lamprey Lethenteron camtschaticum are harvested by subsistence and commercial fisheries in the Yukon-Kuskokwim region of Alaska; however, there is little to no baseline population data available for this species. For mark-recapture and telemetry studies to be effectively utilized to collect information on Arctic Lamprey abundance, migratory and dispersal patterns, and spawning locations, the tags and transmitters used must not impact fish survival, physiology, or behavior. For this laboratory evaluation, survival, incision healing, tag retention, changes in body size, and short- (24 hours) and long-term (43 days) swim endurance were examined for prespawn Arctic Lamprey (N = 216) collected from the lower Yukon River. A total of six treatment groups were evaluated: control, sham surgery, external t-bar anchor tag, and small (0.30 g; 0.1-0.4% tag burden [the ratio of transmitter weight to Arctic Lamprey body weight]), medium (0.57 g; 0.2-0.8% tag burden), and large (1.50 g; 0.6-1.9% tag burden) internal radio transmitters. While all Arctic Lamprey survived tagging and surgical procedures, the mortality hazard of Arctic Lamprey was significantly greater for the large transmitter treatment group compared to the control, t-bar, and sham surgery treatments. Internal scar tissue production, displacement of eggs, and breaks in male testes were found in individuals in all internal transmitter treatment groups. Over the 14-week experimental period, only one t-bar anchor tag and one small transmitter were shed by tagging-evaluation Arctic Lamprey. While no significant differences in healing were found among surgical treatment groups, persistent inflammation was observed at surgical incision sites as well as erosion of the skin at antenna protrusion locations. Most Arctic Lamprey declined in total length (mean relative change = -5.02%) and wet weight (mean relative change = -9.65%) over the experimental period, with no differences among treatments. While treatment group was not a significant predictor of swim endurance, higher tag burden resulted in reductions in swim duration at 24-hours, but not 43-days post-treatment. My results indicate that t-bar anchor tags and internal radio transmitters (maximum tag burden = 1.3%) do not impact survival, changes in body size, or swimming endurance of prespawn Arctic Lamprey and can be used to monitor spawner abundance and migratory patterns in the Yukon River.