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Orcasphere » Brad Hanson on orca diet
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Brad Hanson on orca diet

Monster Jam, Brad Hanson, 07/04/05

Diet of southern resident killer whales

Inferences from prey samples and sensors deployed on killer whales
Time-depth-recorder deployments in southern residents

  • Baird and Hansen+? (2005) J Canadian Zoology
  • 40 deployments from 1993-2002
  • ~10.5 minutes median record duration
  • L87 Haro Strait example record: 2 dives to 100m with velocity spikes near deepest point; 2 dives to 20m with velocity spikes (~4m/s peak)
  • overall bimodal distribution with most dives to 25m or 100-150m…
  • compare with fisheries data: Quinn says sockeye usually at 16m, Chinook ~70m; Horne says larger echosounder targets are common at 100m (trawl there gave dogfish and juvenile salmon)

2002 crittercam on J25 (1.5 hr data total) example from S Lopez

  • Blows bubbles before surfacing
  • Blow hole puckers during vocalization

Foraging behavior (samples/behavior metric) is more often defined by low energy behavior (slow convergence) than high

Molecular Genetic analysis
(scales and tissue ~77 samples; about 150 if you include fecal, mucous, regurgitations)

Most samples collected N/S of false bay, SJI

Primary seasonal prey species:

  • Chinook (primarily in June-Aug)
  • Little data from Sept/oct
  • Chum in Oct/Nov/Dec
  • NO sockeye or pinks
  • ==> are seals and orcas partitioning resources?

From which river systems did the ingested chinook come? (L. Weitkamp, unpublished)
base on (genetic sampling) via coded wire tag program?

  • May: southern puget sound fish! (only one Fraser)
  • June-Sept:
  1. Predominance of Fraser
  2. upper fraser first in  mid Jun-aug; then South Thompson;  then mixed in Sept
  3. One central valley ca
  4. Some N sound, but minimal S sound

Fecal data from sep and oct and nov include evidence of dover sole and lingcod

Planned collections in 2007: June and Sept
Desire for May and Oct collections

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