The ASL Zooplankton Acoustic Profiler (ZAP) located at the base of the slope of the Fraser Delta recorded this hourly image of echo-sounder backscatter between 4:00 and 5:00 UTC September 5, 2011 (21:00 – 22:00 PDT September 4, 2011, just after dusk and at rising tide). The image reveals a dense school of large fish between 10 and 20m depth, and many individual fish...