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Arctic-Yukon-Kuskokwim Edge Codes

Last modified on Feb 25, 2021

Edge growth codes are recorded in the Arctic-Yukon-Kuskokwim Region to track and facilitate aging of resorbed scales and are not included in AYKDBMS. Resorption is common from mature salmon in the region and found in scales collected from upriver locations and those on or near the spawning grounds. An edge growth code is used for scales that have moderate resorption and an additional saltwater annulus was added.

Resorption rates:

  1. Minimal — edge growth code not recorded and at least part of the last annulus is visible.
  2. Moderate — edge growth code is assigned and no part of the last annulus is visible. Only one annulus is interpreted as resorbed.
  3. Extensive — edge growth code not recorded and reader unable to assess number of missing annuli 0, 1, or more; saltwater age not estimated and error code 6 (resorbed) is assigned.

The edge growth code is estimated by measuring the width of the last incomplete annual growth zone, on the scale margin, relative to the previous complete annual growth zone. All scales are examined, and the measurement is made from the widest portion of the last annual zone. Measurements are rough approximations of the relative widths and are quickly made by eye. The reader may use distance between two fingers as a guide. Usually the rate of resorption is not consistent among scales or around the scale circumference. The edge growth code is a relative measurement of saltwater plus growth following the last visible annulus. Edge growth codes range from 2 through 8 from less to more saltwater plus growth. Evaluating whether an annulus was resorbed requires knowledge of expected saltwater plus growth, preferably acquired by aging non-resorbed scales within the same drainage. Most Chinook salmon, with non-resorbed scales, returning to the region have little, if any, saltwater plus growth.

Table 1. — Edge growth codes used for resorbed scales.

Code Growth measurement compared to previous year
2 less than ¼
3 about ¼
4 almost ½
5 about ½
6 more than ½
7 almost same
8 equal to or greater

On this page:

Edge code 4

Magnified scale collected from a 765 mm male Chinook salmon
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Magnified scale collected from a 782 mm male Chinook salmon
Figure 2. Click image for more information
Magnified scale collected from a 696 mm male Chinook salmon
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Magnified scale collected from a 686 mm male Chinook salmon
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Magnified scale collected from a 873 mm female Chinook salmon
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Edge code 5

Magnified scale collected from a 668 mm Chinook salmon
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Magnified scale collected from a 796 mm Chinook salmon
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Magnified scale collected from a 728 mm male Chinook salmon
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Magnified scale collected from a 853 mm male Chinook salmon
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Magnified scale collected from a 778 mm male Chinook salmon
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Magnified scale collected from a 658 mm male Chinook salmon
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Magnified scale collected from a 681 mm male Chinook salmon
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Magnified scale collected from a 838 mm female Chinook salmon
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Magnified scale collected from a 831 mm male Chinook salmon
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Magnified scale collected from a 829 mm female Chinook salmon
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Magnified scale collected from a 614 mm male Chinook salmon
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Magnified scale collected from a 614 mm male Chinook salmon
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Magnified scale collected from a 709 mm male Chinook salmon
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Magnified scale collected from a 826 mm female Chinook salmon
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Edge code 6

Magnified scale collected from a 860 mm Chinook salmon
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Magnified scale collected from a 639 mm female Chinook salmon
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Magnified scale collected from a 808 mm female Chinook salmon
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Magnified scale collected from a 625 mm Chinook salmon
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Magnified scale collected from a 838 mm female Chinook salmon
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Magnified scale collected from a 955 mm male Chinook salmon
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Magnified scale collected from a 924 mm female Chinook salmon
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Magnified scale collected from a 613 mm male Chinook salmon
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Magnified scale collected from a 689 mm male Chinook salmon
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Magnified scale collected from a 870 mm female Chinook salmon
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Magnified scale collected from a 894 mm female Chinook salmon
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Magnified scale collected from a 732 mm female Chinook salmon
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Magnified scale collected from a 747 mm female Chinook salmon
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Magnified scale collected from a 569 mm male Chinook salmon
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Magnified scale collected from a 746 mm male Chinook salmon
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Magnified scale collected from a 856 mm male Chinook salmon
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Magnified scale collected from a 738 mm female Chinook salmon
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Magnified scale collected from a 873 mm female Chinook salmon
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Magnified scale collected from a 796 mm female Chinook salmon
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Magnified scale collected from a 719 mm male Chinook salmon
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Magnified scale collected from a 789 mm female Chinook salmon
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Magnified scale collected from a 809 mm male Chinook salmon
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Edge code 7

Magnified scale collected from a 798 mm Chinook salmon
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Magnified scale collected from a 758 mm Chinook salmon
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Magnified scale collected from a 863 mm Chinook salmon
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Magnified scale collected from a 818 mm female Chinook salmon
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Magnified scale collected from a 661 mm male Chinook salmon
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Magnified scale collected from a 840 mm female Chinook salmon
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Magnified scale collected from a 759 mm female Chinook salmon
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Magnified scale collected from a 824 mm male Chinook salmon
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Magnified scale collected from a 729 mm male Chinook salmon
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Magnified scale collected from a 704 mm female Chinook salmon
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Magnified scale collected from a 837 mm female Chinook salmon
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Magnified scale collected from a 668 mm male Chinook salmon
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Magnified scale collected from a 660 mm male Chinook salmon
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Edge code 8

Magnified scale collected from a 765 mm Chinook salmon
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Magnified scale collected from a 766 mm female Chinook salmon
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Magnified scale collected from a 879 mm female Chinook salmon
Figure 57. Click image for more information
Magnified scale collected from a 689 mm male Chinook salmon
Figure 58. Click image for more information
Magnified scale collected from a 765 mm female Chinook salmon
Figure 59. Click image for more information