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CONFERENCE SCHEDULE UPDATES & CHANGES: As a result of the prolonged government shutdown, we experienced a number of cancellations and changes to the schedule. Cancellations and changes are listed here (as of January 26, 2019). 
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Monday, January 28 • 11:20am - 11:40am
(FISHERIES: GREAT LAKES 1) Mark-Recapture Validation of Pectoral Fin Ray Age Estimation for Lake Sturgeon

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AUTHORS: Brad Utrup, Jan-Michael Hessenauer, Andrew S. Briggs, Todd Wills, Michael Thomas (retired) – Michigan Department of Natural Resources

ABSTRACT: Age estimation is a fundamental part of fisheries management; critical for evaluations of growth, mortality and recruitment.  Validation of ages obtained from age estimation of hard structures is a necessary part of the ageing process in order to better understand the magnitude of error and bias associated with structure interpretation.  Validation studies on large-bodied and long-lived species such as Lake Sturgeon Acipenser fulvescens are challenging.  We utilized a 20-year mark-recapture dataset from Lake St. Clair and the St. Clair River, Michigan, USA to validate pectoral fin ray age estimates from 51 individuals that were sampled twice. The time at large ranged from 2 to 17 years between capture-recapture events.  All fin rays were aged by two separate readers (agreement rate 94.1%).  Samples were divided into four quartiles based on mean annual growth rates during their time at large.  Age error was defined as the difference between the age of the fish at first and second capture and the number of years at large.  No difference in time at large existed among the four groups, but age error differed among the four groups.  Furthermore, age error did not differ from zero for the two fastest growing quartiles but did differ significantly from zero for the two slowest growing quartiles.  We conclude that for Lake Sturgeon growing faster than 3 cm/year (generally less than 100 cm in TL) pectoral fin rays provide valid age estimates.  Managers should consider the growth rates of Lake Sturgeon in their populations for determining a size threshold for utilizing fin rays for age estimation.

Monday January 28, 2019 11:20am - 11:40am EST