New paper by UW colleagues entitled “Interpreting
Interestingly, according to a report to NOAA/NWFSC by Baird et al, 2003 (STUDIES OF FORAGING IN “SOUTHERN RESIDENT” KILLER WHALES DURING JULY 2002: DIVE DEPTHS, BURSTS IN SPEED, AND THE USE OF A “CRITTERCAM” SYSTEM FOR EXAMINING SUB-SURFACE BEHAVIOR) SRKWs spend >97% of their time at depths of less than 30m.
This suggests any future deployment of horizontal echosounders should aim to ensonify a depth range centered on ~25m (e.g. 5-45m or 10-40 m). Compared to the estimated orientation and surveyed depth range of our 2008-9 salmon-SRKW echosounder pilot studies, we may want to measure inclination more carefully to (a) center the survey on the mean summertime depth range of Chinook and (b) avoid ping reflections from surface waves, boats, and bubbles (which may have confused interpretations of targets >100 m from the transducer). Here’s my diagram for the situation in 2008-9 in which we were centered on 15 m and ensonified a maximum depth range of ~0-30m (in other words, we may have been aiming a little high):