1 / 34

Southeast Alaska Herring

Southeast Alaska Herring. November 5-6, 2013 Anchorage, Alaska by Detlef Buettner Coded Wire Tag Lab Supervisor Alaska Department of Fish and Game Division of Commercial Fisheries. “Age Sex Length” H erring collected in 5 gallon buckets. Gender determination. Measuring. Weighing.

cade
Download Presentation

Southeast Alaska Herring

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Southeast Alaska Herring November 5-6, 2013 Anchorage, Alaska by Detlef Buettner Coded Wire Tag Lab Supervisor Alaska Department of Fish and Game Division of Commercial Fisheries

  2. “Age Sex Length” Herring collected in 5 gallon buckets

  3. Gender determination

  4. Measuring

  5. Weighing

  6. Tray up

  7. Plucking scales

  8. Mounting scales to slide

  9. Preferred areas for scale sampling ( increasing order of preference) Herring scales: 15 per slide, 1 scale per fish

  10. Scale terminologyFocusAnnulusSummer growthPlus growthBasal line

  11. Aging errors at the MTA lab: error Red oval indicates an error (not a true annulus). Correct age is 5 (not 6).

  12. Juvenile checks are much smaller than first annulus. The juvenile check below is about same size as a scale from a 40 mm juvenile herring. First Annulus Juvenile Check

  13. Scale development in Pacific Herring Scales of a 31mm Pacific herring (Courtesy of NMFS, sampled at Auke Bay, Aug 21st 1976) 31mm Herring (on top)

  14. 45mm herring (Courtesy of NMFS, sampled at Little Port Walter, September 8th, 1966)

  15. 60 mm Pacific herring (Courtesy of NMFS, sampled at Pybus Bay, Oct 25th, 1964)

  16. Scale development in Pacific Herring Scales of a 31mm Pacific herring (Courtesy of NMFS, sampled at Auke Bay, Aug 21st 1976) 31mm Herring (on top)

  17. Three scales from 50 herring were measured.Average scale length plotted against body length

  18. Validation – determining when annuli form One and two year old herring (ADF&G, sampled in Sitka, February 25th, 2011)

  19. Validation Method: Sampling monthly in the spring Scale of one-year old herring – No annulus present in April No Annulus visible yet (ADF&G, sampled in Sitka, April 14th, 2011)

  20. Scale of one-year old herring New annulus has formed by mid-May (ADF&G, sampled in Sitka, May 19th, 2011)

  21. Late Spring samples When new annulus has formed Four-year old herring Sitka - March, 2012 Three-year old herringSitka - June 22nd, 2012

  22. Adult scale projected on a Microfiche reader

  23. First annulus is typically the size of a fist 42X magnification on microfiche

  24. Hamburg fish market

  25. Market screamer

  26. Extent of aging error: • 1999-2002 no significant errors • 2003-2005 over-aging predominantly by one year • 2006-2010 over-aging predominantly by two years • All SE Alaska stocks were affected by the aging drift (gradual change in methodology) • Determined all 1999-2010 herring scales needed to be re-aged to ensure data consistency

  27. What we did to correct the aging errors: • Examined scale ages from 1998 (pre-Lab ages) • Re-examined and defined herring scale aging methodology • Created aging test on 1998 calibration scales • Re-aged 70,000+ scales for years 1999-2010 • Spot checked selected years - 1980-1997 Sitka and Seymour • Method verification at Pacific Biological Station, Nanaimo, DFO (June 2011)

  28. What we are doing to prevent this problem from occurring again: • Validate the scale aging method • Follow established aging protocol • All agers must pass an 80% precision test on 1998 calibration scales • 10% spot check performed on all aged herring samples • Re-read all samples that fail 80% precision • Prevent reader isolation through teamwork • Teach all lab technicians basic herring aging skills • 200 scale spot check with Nanaimo and ADF&G Lab in Cordova (2013)

  29. Additional projects: • Develop a library of scale images

More Related