Comparing two bony structures for aging lake trout from Lake Michigan

Stacy-Duffy, William L.; Czesny, Sergiusz J.

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https://hdl.handle.net/2142/124116 Copy

Description

Title

Comparing two bony structures for aging lake trout from Lake Michigan

Author(s)

• Stacy-Duffy, William L.
• Czesny, Sergiusz J.

Contributor(s)

,

Issue Date

2024-09-12

Keyword(s)

• Fisheries Management
• Population Metrics
• Lake Trout
• Lake Michigan

Geographic Coverage

Illinois

Abstract

The collection of accurate age data is a critical tool in fisheries management as it is essential for understanding population metrics such as growth (DeVries and Frie, 1996), maturity (Madenjian et al.,1998), population age structure (Burnham-Curtis and Bronte, 1996), and mortality (Sitar et al., 1999). Age data are also a critical input to statistical catch-at-age models (SCAA), an intensive tool used to assess fish stocks and forecast the population-level impact of management decisions (e.g Caroffino and Lenart, 2011; Ebener et al., 2021). Accurate age estimates are required for these tools to be useful to managers, especially for longer-lived fishes such as lake trout (Salvelinus namaycush). A dramatic increase in lake trout natural reproduction and recruitment has been observed in the Illinois waters of Lake Michigan in the past two decades (Patterson et al., 2016) after 40 years of stocking efforts failed to result in any meaningful successful spawning. All lake trout currently stocked in Lake Michigan are given a coded wire tag (CWT) containing a 6-digit code referring to their specific stocking event. Coded-wire tagging allows managers to collect precise age data to assess growth and mortality (e.g., Kornis et al., 2019; Clark et al., 2023) with complete certainty. As naturally reproduced lake trout increase in abundance, managers need reliable age structures that can be collected from surveyed wild fish to estimate population age structure, growth, and survival in the absence of CWT data. Quantifying these metrics for the wild population requires acquiring age data from bony structures, traditionally otoliths (Campana and Thorrold, 2001) which are often considered the most accurate hard structure for aging fish. However, otoliths can be rendered unreadable when their typical form of calcium carbonate, aragonite, is replaced by an alternative crystalline form known as vaterite (Bowen II et al., 1999). The presence of vateritic otoliths cause over one third of sampled fish to be excluded from analysis due to the lack of an age estimate (Osbourne et al., 2022). Recent research has shown the efficacy of maxillae for providing accurate ages for lake trout (Wellenkamp et al., 2015; Hemmelgarn et al., 2022). This led fishery managers with Illinois Department of Natural Resources (IDNR) to seek to understand the potential for maxillary bone sections to provide consistent and accurate ages, without being subject to the loss of data related to otoliths being unreadable. Existing fish with CWTs provide an opportunity to observe aging structures from known-age fish to validate aging procedures, an important step in age determination methods (Beamish and McFarlane, 1983). The objective of this study was to assess the utility of lake trout maxillae and otoliths for aging and subsequently provide recommendations to the IDNR as to the most effective structure to collect from lake trout in future surveys.

Publisher

Illinois Natural History Survey

Series/Report Name or Number

NHS Technical Report 2024 (16)

Type of Resource

text

Language

eng

Sponsor(s)/Grant Number(s)

Federal Aid Project F-196

Copyright and License Information

This document is a product of the Illinois Natural History Survey, and has been selected and made available by the Illinois Natural History Survey and the University Library, University of Illinois at Urbana-Champaign. It is intended solely for noncommercial research and educational use, and proper attribution is requested.

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