Cooperative Fish and Wildlife Research Units Program: Wisconsin Fishery
Education, Research and Technical Assistance for Managing Our Natural Resources

Pectoral fin rays are commonly used as a non-lethal method for estimating age of lake sturgeon Acipenser fulvescens. While fin rays generally underestimate age of older lake sturgeon, fin rays could provide useful estimates of growth rate for younger fish within a population. Our objective was to determine if lake sturgeon growth rates estimated from fin rays were similar to growth rates observed from recaptures of lake sturgeon tagged with passive integrated transponders (PITs). Lake sturgeon were sampled in 2012-2013 via electrofishing on the Menominee River, where the Wisconsin and Michigan Departments of Natural Resources maintain a long-term PIT tagging program. Parameters from a von Bertalanffy growth model were used to describe growth rates estimated from fin rays (range of fin ray ages = 4 to 34). For recaptured fish, growth rates were quantified as change in length during time at large. Preliminary results suggest growth rates estimated from fin rays (mean = 1.18 in/yr) are substantially higher than rates observed from PIT tag recoveries (mean = 0.47 in/yr). This difference is consistent with underestimating lake sturgeon age from fin rays. Differences in growth rates between the two methods were inversely related to lake sturgeon total length, suggesting that fin ray growth estimates were more reliable for larger (≥ 50 in), older lake sturgeon, only because these fish were growing very slowly. Fin rays are probably not useful for estimating growth rates of lake sturgeon and we suggest that continued use of mark-recapture with PITs offers the best method for describing growth and survival in most lake sturgeon populations.