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Wednesday, January 27 • 1:40pm - 2:00pm
Fire The Laser! Determining Natal Origins of Juvenile Steelhead Using Otolith Chemical Analysis

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AUTHORS: Nicole Watson*, Central Michigan University; Steven Hummel, Central Michigan University; Jory Jonas, Michigan Department of Natural Resources; James Student, Central Michigan University; Kevin Pangle, Central Michigan University

ABSTRACT: Lake Michigan steelhead Oncorhynchus mykiss are a mix of hatchery-produced and wild fish, the latter originating from many different natal tributaries within the lake basin. Mixed stock populations can complicate conservation and management due to unequal contributions from various stocks, thus making it necessary to understand the natal origins of such populations. We evaluated the use of otolith chemistry as an approach to identify the natal origin of Lake Michigan steelhead. Using laser-ablation inductively coupled plasma mass spectrometry, we analyzed the otoliths of juvenile steelhead collected in 2013 and 2014 from 46 Michigan and Wisconsin tributaries of Lake Michigan. We found distinct chemical signatures occurring between fish from different natal streams and hatcheries that could be used to accurately predict their natal origins. The study included the analysis of calcium the major cation in otolith carbonate, and the trace elements magnesium, manganese, copper, zinc, strontium, barium, and lead. Strontium was found to be the most important trace element for discrimination, with highest values generally occurring in otoliths of fish from the Manistee River. A variety of the other trace elements concentrations are indicative of a number of specific streams. Classification accuracies were found to be higher at the regional scale versus the individual stream level both spatially and temporally with the year class of fish having little effect. Our results clearly demonstrate the utility of otolith chemistry and pave the way for future studies to determine the natal origins of adult steelhead, thus benefiting the management of both steelhead and their natal habitats.

Wednesday January 27, 2016 1:40pm - 2:00pm EST
Gerald Ford