Otolith microchemistry as a stock identification tool for adult Lake Michigan steelhead

Session: Poster Session

Ben Breaker, Central Michigan University, [email protected]
Kevin Pangle, Central Michigan University , [email protected]
Jory Jonas, Michigan Department of Natural Resources, [email protected]
James Student, Central Michigan University, [email protected]

Abstract

Steelhead (Oncorhynchus mykiss) often arise from multiple, spatially distinct natal sources which coexist for most of their adult life in a large body of water. The multitude of natal sources which contribute to mixed stock fisheries are often complex and provide challenges to interpretation of recruitment and harvest allocations. Such is the case for steelhead populations in Lake Michigan, which are currently supported by extensive stocking from 5 hatcheries and substantial natural reproduction from numerous (40+) tributaries. The site-specific contributions of each of these natal sources to the overall fishery are not well understood. We used otolith microchemistry to identify the natal origins of angler harvested adult steelhead in Lake Michigan. Specifically, we utilized laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to quantify the concentration of 7 descriptive trace elements in each adult otolith along a transect corresponding to the juvenile period of development. Natal origins were assigned to adult fish using a previously developed random forest classification models built with data from known-origin juvenile steelhead across the Lake Michigan basin. An understanding of the stock structure and the population dynamics of steelhead in Lake Michigan will greatly improve our ability to sustainably and effectively manage Steelhead fisheries.