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Orcasphere » Habitat use
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Habitat use

Gregg Schorr for Brad, dive behavior

  • Is dive depth related to prey preference?
  • Do dive rates vary between pods, day/night, years?
  • Is frequency of max dive depth constant over time?

Prey field mapping in Sept, 2004 (after sockeye, during fall Chinook run): big targets are near middle of water column (>100m); prey assemblages different in Haro Strait?

Wild Salmon Center identified rivers with multiple runs and little development that could be wild salmon “strongholds” or refuges during an age of global warming.

40 deployments 93-2000, 419 hours data, median duration of deployment 10.5hrs.  Velocity spikes are often associated with deepest portion of dive (and some shallow dives).

What are accelerations in shallow dives?  (Tried critter cam)

All individuals old/young and across pods have similar dive profiles and all swam slower at night, but males dive deeper than female adults (but only during day).  There is also an inexplicable change in depth of dives over the years.

Focal follows show they don’t go to the bottom (e.g. 150m dive in 300m water).  This summer we’ll use new tags with a hydrophone and body orientation sensors.  Also planned are satellite tagging efforts.

Rich Osborne, long-term patterns in SRKW residency

43,000 sightings in the OrcaMaster database 1980-2008 (biased towards summer initially, but in last 2 decades it’s become more balanced).  Puget Sound is Admiralty Inlet and Deception Pass south.

After L pod members spent ~a month in Dyes Inlet, they extended their stay in inland waters ever since.  They didn’t often do that before.  This suggests they can adapt to different prey (e.g. Chilco Creek Chum) when stressed (there was only chum to eat in Dye’s Inlet).

NW Straits and Puget Sound seem to be getting more attention in last decade compared with previous 2 decades.  We should be spending all PS salmon restoration  money for those wild rivers.

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