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EFFECTS OF ENVIRONMENTAL AND BIOLOGICAL FACTORS ON MIGRATORY SEA LAMPREY CATCHABILITY AND ABUNDANCE ESTIMATION
2U. S. Fish and Wildlife Service, Marquette Biological Station, 3090 Wright St., Marquette, MI 49855
3Fisheries and Oceans Canada, Sea Lamprey Control Centre, 1219 Queen Street, East Sault Ste. Marie, ON P6A 2E5
4U. S. Geological Survey, Great Lakes Science Center, Hammond Bay Biological Station, 11188 Ray Road, Millersburg, MI 49759
Sea lamprey population trends in the Great Lakes are tracked by trapping migratory adults in tributaries and using mark and recapture techniques to estimate abundance. Understanding what environmental and biological factors influence sea lamprey catchability is crucial to developing efficient trapping methods and reliable abundance estimates. We analyzed data from trapping sites located on 8 Great Lakes tributaries and examined how water temperature, discharge, sex, and length influenced sea lamprey apparent survival and capture probability. Sea lamprey apparent survival was negatively associated with water temperature in all tributaries. Additionally, the odds of small sea lamprey (≤45 cm) remaining available to capture were 39% (95% CI: 63% decrease – 1% increase) less than large (>45 cm) lamprey odds. These observed relationships were used to investigate if bias in abundance estimates using the pooled-Petersen estimator and Jolly-Seber models was expected to be similar across trapping locations or influenced by variable environmental conditions and biological traits. Pooled-Petersen abundance estimates had a positive bias when datasets were generated from simulated populations with empirical relationships between environmental characteristics and catchability. The degree of bias depended upon changes in stream warming patterns and was not consistent among trapping locations. Jolly-Seber models using data from either weekly-batch-marked or uniquely-marked individuals generated abundance estimate with low bias when data quality was high, but performed poorly in scenarios with few recaptured sea lamprey.