East Grand Lake Lake Trout Spawning Study PDF Download

Lake trout populations were extirpated from the lower four Great Lakes by 1960 and from Lake Champlain by 1900. The decline of lake trout populations fueled a wave of restoration-based research that spanned the Great Lakes and filled in many of the gaps in our knowledge of lake trout behavior and ecology. However, remarkably little is known about lake trout spawning behavior, even less about sex-specific differences in spawning site use. Lake trout use specific spawning sites, and may return to the same site year after year. More males are caught on spawning sites than females and are present at spawning sites earlier in the spawning season. The focus of this project is to describe the spawning movements of male and female lake trout within and among spawning seasons and spawning sites. I used acoustic telemetry in Lake Champlain to look at specific questions of spawning site fidelity and whether or not there were differences in male and female movements. I hypothesized that males show site fidelity and remain at a preferred site during the spawning season, whereas females 'sample' multiple spawning reefs to maximize their reproductive success. I established an acoustic telemetry array of ten acoustic receivers placed over eight spawning sites and implanted acoustic transmitters (tags) in 44 male and 48 female lake trout over two years. During two spawning seasons, males spent more time on spawning sites than females. Both male and female lake trout that were active on monitored sites during the spawning season selected a single preferred site. There was no difference in the number of sites visited by males and females. Of the lake trout detected during both spawning seasons, most returned to their capture site in the subsequent spawning season, showing evidence of site fidelity. I also developed a binomial rolling residence test (BRR test) to improve the current method of assessing the duration of a fish’s residence at a single receiver. I measured daily detection probabilities (DP) at a given distance from a receiver site. The BRR test evaluates a tag’s residence every minute by moving a one-hour time window centered on time t across the duration of the data. The daily DPs are incorporated into a binomial test of the null hypothesis that a fish is not within x meters of the receiver at time t. I performed a 48-hour stationary residence test using two onsite tags and two offsite tags and compared the performance of the BRR test to three residence assessment methods found in the literature. The results showed that the BRR test performs better than all of the time-threshold residency evaluations in our 48-hour stationary residence test. We suggest that this method has the potential to advance the field of telemetry by improving the interpretation of telemetry data.