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Aging Salmon

Aging Salmon. Dion Oxman Dayna Norris Peter Hagen. Why Age Salmon?. ● Stock Assessment ● Fisheries Management ● Growth, Demography, & Life History Data RE: Longevity & Survival ● Determine broodyear of hatchery fish that have had similar thermal

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Aging Salmon

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  1. Aging Salmon Dion Oxman Dayna Norris Peter Hagen

  2. Why Age Salmon? ● Stock Assessment ● Fisheries Management ● Growth, Demography, & Life History Data RE: Longevity & Survival ● Determine broodyear of hatchery fish that have had similar thermal marks applied over multiple broodyears.

  3. 0.3 No freshwater years, three ocean years. 1.2 One freshwater year, two ocean years. 2.1 Two freshwater years, one ocean year. Aging Lingo: The European Age Designation System # Freshwater Years . # Ocean Years Add 1 year for time spent in gravel to estimate brood year. These are all four year old fish, but each had a different life history. So how are ages estimated? How distinguish between fresh & salt water residence times?

  4. FW Growth Relatively small spaces between rings (slow growth) SW Spring / Summer Growth Enhanced growth. Spaces between rings relatively wide. SW Autumn / Winter Growth Ring distances decrease relative to spring/summer, but larger than those observed in the FW zone. “ANNULUS” Origin / Focus Estimating Age From Hard Parts ●Structures useful for aging grow incrementally. ● Incremental growth (e.g. “rings”) affected by environment & seasons. ● The Relative changes in these ring patterns are used to estimate age. Spr/Sum Growth + Aut/Win Growth = 1 Year

  5. Aging Salmon From Scales PROS ■ Accurate ■ Quickly processed ■ Large Sample Sizes ■ Multiple samples per fish CONS ■ “Preferred Area” ■ Scale Loss & Damage ■ Scale Regeneration ■ Scale Resorption

  6. Types of Otoliths Asteriscus Sagitta Lapillus Aging Salmon From Otoliths PROS ■ Not exposed to wear ■ Bilaterally Symmetrical ■ Uninterrupted record of life history ■ Provides growth information for a variety of temporal scales (daily to annual) CONS ■ Removal ■ Variable ring detectability ■ Moderate to intensive preparation

  7. Techniques for Aging Salmonid Otoliths 1) Reflected Light ● Whole otolith ● Dissecting microscope ● Water or glycerin enhances rings 2) Transmitted Light ● Ground & Polished otoliths ● Compound light microscope ● Daily rings & thermal mark recovery

  8. Opaque Zone (Spring/Summer) Translucent Zone (Fall/Winter) “Annulus” Reflected Light Whole Otolith Transmitted Light Polished Otolith Ring appearance differs with light source. Spr/Sum Growth (Opaque Ring) + Aut/Win Growth (Clear Ring) = 1 Year

  9. Spring/Summer Growth Reflected Light Origin: Primordia AGE: 2.2 FW Annuli 2 Clear & relatively narrow winter rings occurring close together (slow growth) & near the primordia SW Annuli 2 Clear & relatively wide winter rings occurring farther apart

  10. TIP: Remember Life History Sockeye, Chinook & Coho ■ Fry spend first 1 to 3 years in freshwater ■ Expect to see freshwater annuli Pink & Chum ■ Fry enter the sea early in development = No Freshwater Growth ■ Chum may spend extended periods of time in transition (estuarine) zones ■ Pinks w/ strict 2-year life cycle

  11. 2.2 Sockeye

  12. 1.3 Sockeye

  13. SW SW SW 0.3 ChumNo freshwater growth

  14. FW FW FW SW SW Age 3.2

  15. FW SW SW SW Age 1.3

  16. Crystalline Otoliths Many hatchery fish are otoliths are “crystallized”, which can make them difficult to age.

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