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Methods for Analyzing Chinook Scales in Coastal and Interior Oregon: Insights from a Growing Project

This document outlines the methodologies used in the Fish Life History Analysis Project, focusing on Chinook salmon scales in Oregon's coastal and interior regions. It discusses project history, transitions, scale preparation techniques, and methods for age determination of salmon. Key techniques include mounting scales on gummed cards, creating plastic impressions, and employing digital imaging systems. Challenges such as sample size, scale quality, and life history diversity are addressed, highlighting the project's adaptation to evolving needs in Chinook monitoring and analysis.

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Methods for Analyzing Chinook Scales in Coastal and Interior Oregon: Insights from a Growing Project

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  1. Methods for analysis of Chinook scalescoastal and interior Oregon The Fish Life History Analysis Project Ben Clemens Lisa Borgerson Kanani Bowden Stephanie Gunckel

  2. Fish Life History Analysis Project • Project history • Project transitions • Bottom-line: Chinook (and other spp.) monitoring • “Small, developing project with a big (and growing) plate”

  3. Scale Preparation • Most scales mounted on gummed cards • Plastic impressions made with a heat press • Scales of juveniles mounted on glass slides • Viewed with microfiche projector • Digital image system (Image Pro Plus, FlashPoint frame grabber, Leitz microsope, Cohu B&W camera)

  4. Fish Age • Age salmon by the number of winters • Fall/winter spawning salmon: Add “1” for the first winter

  5. Accuracy and Precision Accuracy • Test readers with known age scales--tagged fish (CWT, PIT) • Multiple readers (catch recording errors, lapses in judgment) Precision • Multiple readers-agree on interpretation diffs • Train by reading scales read by prev. readers • Test on a standard set of scales

  6. Validation • Known age tagged fish • Natural marks • Pedigree study • Mark and recapture • Marks on structure, chemical or temperature induced • Beamish, R.J. and G.A. McFarlane. 1983.. Trans. Am. Fish. Soc. • Campana, S.E. 2001. J. Fish Biol.

  7. Challenges • Sample sizes • Scale quality • Resorption/regeneration • Unclipped hatchery fish • Within-basin life history diversity • Ocean entrance: check vs. annuli • “Reservoir” life histories • South-migrating stocks: less distinct annuli • Lack of “known” age/disposition samples: Validation

  8. Challenges • “Small, developing project with a big (& growing) plate” • Ability to adapt (learn, grow, train new staff): challenging, given workload.

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