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Identifying Individual Bowhead Whales Through Aerial Photography

Identifying Individual Bowhead Whales Through Aerial Photography. Supporting organizations. National Marine Mammal Laboratory , Alaska Fisheries Science Center, NOAA Fisheries Service, Seattle, Washington LGL , Ltd. Environmental Research Assoc., King City, Ontario, Canada

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Identifying Individual Bowhead Whales Through Aerial Photography

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  1. Identifying Individual Bowhead Whales Through Aerial Photography

  2. Supporting organizations • National Marine Mammal Laboratory, Alaska Fisheries Science Center, NOAA Fisheries Service, Seattle, Washington • LGL, Ltd. Environmental Research Assoc., King City, Ontario, Canada • North Slope Borough, Dept. of Wildlife Management, Barrow, Alaska • Minerals Management Service, Environmental Studies Program, Alaska Outer Continental Shelf Region, Anchorage, Alaska • Cascadia Research Collective, Olympia, Washington

  3. There are currently over 17,000 images of bowhead whales in collections archived at LGL and NMML. Over the past 30 years, aerial surveys have been conducted mostly near Point Barrow during the spring migration and in the Beaufort Sea in summer. Available images of bowheads

  4. Whale lengths Whale images are measured for length and corrected relative to camera lens, aircraft altitude (calibrated), and any known photogrammetric biases. 15.5 m

  5. Growth of individual whales • Calves are 4.75 - 5.0 m long in May, and 6.25 - 6.5 m long by October. • Yearlings in May are 6.5 - 8.0 m long. • Small whales (~9.5 m) grow 22 - 44 cm/yr. • Medium size (~12 m) grow 12 - 15 cm/yr. • Large whales (~15 m) grow 0 - 5 cm/yr.

  6. Components of categorizing bowhead images

  7. Four zones used to categorize areas on a bowhead image Rostrum zone (1) Mid-back zone (2) Lower-back zone (3) Fluke zone (4)

  8. Sizes of marks used in categorizing identifiability

  9. Identifiability by zones Rostrum zone unmarked (U-) Lower-back zone (H+) Fluke zone (H+) Mid-back zone (U+) Large, fairly distinctive mark Large, non- distinctive mark One medium not unique mark

  10. Image quality Rostrum zone is quality 1+ (= clearly visible) Lower-back zone is quality 2+ (= adequately visible) Fluke zone is quality 1+ (=clearly visible) Mid-back zone is quality 2+ Some of this zone is obscured by splash

  11. Computer-assisted matching program • Because the number of photos in the catalog has been growing, it is becoming necessary to increase matching efficiency through a computer program that prioritizes most likely matches.

  12. Applications of results from bowhead photo-identification • Abundance estimates • Growth rates of individual whales • Calving intervals • Population dynamics • Stock structure

  13. Abundance Estimates

  14. Resightings of adult whales with calves indicates calving intervals of 3-4 years

  15. Survival probability is remarkably high for bowheads (0.95 to almost 1.00); some bowheads live for over a century

  16. Seasonal distribution of bowhead sightings through the spring migration near Barrow

  17. Stock-structure issues

  18. Resighting dates for bowheads seen on more than one year during the spring migration

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