FIELD COMPARISON OF EEL-LADDER-STYLE AND TRADITIONAL SEA LAMPREY TRAPS
Eel-ladder-style traps (ELST) – inclined ramps with vertical pegs and trickle flow- are a potential addition/alternative to traditional funnel traps for adult lamprey assessment and control. ELST have potential advantages over funnel traps in species selectivity, entrance rate of lamprey that encounter the traps, retention in the trap, safety of trap operation, and ease of baiting with pheromones. As an alternative sea lamprey trapping method, ELST could be used to test crucial assumptions of the adult lamprey assessment program, which relies on unbiased mark-recapture estimates. Field studies are needed to evaluate the effectiveness of ELST used in routine trapping operations and the potential to use ELST for improved sorting of fish in trap-and-sort fishways. Our guiding hypotheses/predictions are i) ELST achieve better lamprey entrance rates than funnel traps with the same attraction flow, ii) added attraction flow at the surface improves capture rate of ELST over funnel traps where natural attraction flow is weak, iii) key assumptions of the current assessment program by mark-recapture are met, and iv) the operational efficiency of trap and sort fishways can be improved by addition of an ELST in the fishway.
1. Determine if entry rate of ELST equals or surpasses that of traditional funnel traps with fingers.
a. In the St. Mary’s River at sites with good and poor current capture rates
b. In two additional rivers (Cheboygan and Ocqueoc Rivers) with current routine trapping operations
2. Test the assumption of no capture/recapture bias of once-trapped-and-marked lamprey
3. Test the effectiveness of adding ELST for sorting lamprey from finfish in an existing trap-and-sort fishway
Objectives 1 and 2: we will install five ELST in close proximity to traditional funnel traps and compare daily capture/recapture rates of marked lamprey at five sites in three rivers: St. Mary’s (three sites), Cheboygan, and Ocqueoc during May/June of Year 1 and 2. Hypothesis ii) will be tested using splashed attraction water at the Cloverland site of the St Mary’s. Five sites, and 30 observation days per season will yield a sample size of 150 replicates/year. Statistical analysis of # captured by trap type will use ANOVA. Experiments to achieve Objective 2 will use procedures from the daily USFWS marking and trapping operation during the lamprey run. Trapped lamprey will be fin-clipped and released, and recaptures noted daily. Hypotheses of possible bias in lamprey behavior relative to traps, such as trap avoidance, will be tested with Chi-square analysis of recaptured marks in the two trap types. For Objective 3, we will add in Year 2 an ELST to the funnel trap in the trap-and-sort fishway in Trail Creek, IN