Differentiating Resident from Migrant Lake Sturgeon in the Lower Niagara River Gregory R. Jacobs1, John A. Sweka1, Dimitry Gorsky2, Michelle Casto-Yerty2, and Betsy Trometer2 1 – USFWS Northeast Fishery Center, Lamar, PA 2 – USFWS Lower Great Lakes Fish and Wildlife Conservation Office, Amherst, NY

Overview Overview Population assessment of lake sturgeon in the Lower Niagara River Mark-recapture Sex, stage, contaminants Habitat selection Herein: Can fixed-station telemetry detect differences in habitat selection of spawning vs. non-spawning lake sturgeon?

Methods

Study Site Lower Niagara River Methods Lower Middle Upper Niagara Falls NY ON Lake Ontario Lake Erie Lower Upper Middle Lower Niagara River

Radio Telemetry Telemetry Equipment What does detection mean? Methods Radio Telemetry Telemetry Equipment ATS R4500 Radio Receiver 8-receiver array Distributed among 3 river areas Max Depth = e(Distance) At 100 m, 8 m max depth Range < River Cross-section Max Depth: 15 – 50 m Channel width: 175 – 700 m What does detection mean? Assume: presence in 100 m radius Lower Niagara River Lake Ontario ON NY Lake Erie

Lake Sturgeon Baited set lines Biological Data, PIT Radio-tag implant Methods Lake Sturgeon Baited set lines Biological Data, PIT Radio-tag implant 616 day, ↑ range, trailing whip, VHF Implanted April, 2012 Sex & stage determination Blood Serum T & E2, Ultrasound, Biopsy Study Period: Apr-18 to Jul-30, 2012

Models Considered Occupancy Modeling Methods Models Considered Occupancy Modeling Site is unit if inference Detection probability modeled explicitly Keep on back burner... Discrete Choice Modeling (Kneib et al. 2011) Fish is unit of inference Presence-only method, site & individual effects Initially, assume whole river ‘available’

Discrete Choice Model Simultaneous analysis of r habitat types Methods Discrete Choice Model Simultaneous analysis of r habitat types Model coefficients = additive effects on η One habitat type as reference category

Results

Telemetry Summary 2012-tagged fish (30) Results Telemetry Summary 2012-tagged fish (30) 27 relocated Apr-18 to Jul-30, 2012 (104 days) 21 kept for analysis Last Day Observed Reproductive Status Day of year Mature M Mature F Immature N 9 3 TL 1,363 mm 1,574 mm 1,387 mm Wt 18.4 kg 33.5 kg 19.8 kg Days 14.6 21.3 13.7 Range 33.8 42.3 56.8

Discrete Choice Model Unconditional model Hypothetical model Results Discrete Choice Model Covariate Effect Day of Year Nonlinear Time Effect Unconditional model Only random fish effect No overall preference Hypothetical model η = β + Rstatus + Time (non-linear) + Fish (random intercept) Still no significant selection (β) ...

Discrete Choice Results Covariate Effect Day of Year Nonlinear Time Effect Covariate Effect Individual Fish Effect Immature M F

Discussion

Lower Niagara River: no Results Can we differentiate migrants from residents using fixed-station telemetry? Lower Niagara River: no Individual heterogeneity >> covariate effects Work-in-progress Low sample size (n=30, too few 2011 returns) Single year, (not quite) 2 seasons Coarse-scale covariates (at best)

Results Can we differentiate migrants from residents using fixed-station telemetry? General approach Promising analytical framework Applicable to large-system fixed telemetry

Acknowledgements Molly Webb, Mariah Talbott, Eli Cureton, USFWS Bozeman, MT Dave Smith, Mary Rocky, USGS Leetown, WV Field Crew: Todd Duval, Brian Layton, Shana Chapman, Paul Bigaj, USFWS Amherst, NY Geoffrey H. Groocock, DVM, PhD, consulted on surgical methods Chris Castiglione, USFWS Amherst, NY

Discrete Choice Coefficients Variable Coeff. SD P 95% CI β (Mid) -2.7 1.94 0.16 -6.5-1.1 β (Uppr) -1.0 1.26 0.42 -3.5-1.5 M (Mid) -0.009 0.44 0.98 -0.9-0.8 M (Uppr) -1.34 0.63 0.03 -2.6--0.1 F (Mid) 0.56 0.60 0.35 -0.6-1.7 F (Uppr) 0.88 0.61 0.15 -0.3-2.1

Habitat Variables Substrate type River Kilometer Temperature Side-scan sonar bottom mapping Bottom types: Hard , Intermediate , Soft River Kilometer Distance from Lake Ontario Temperature Buffalo, NY station Other variables Bathymetry, flow regime, disturbance