Date(s) - 13/May/2021
7:30 pm - 9:00 pm
Pacific great blue herons have been stalking the shores of salmon-bearing rivers in B.C. for millennia, but only recently were we able to peer into the relationship they share with our coast’s most iconic species. Our study started by implanting juvenile salmon with Passive Integrated Transponder (PIT) tags to track their migration to sea, but, much to our surprise, as many as 50% of these fish were disappearing before ever making it out of the river. To track down where the salmon ended up, we scoured the forest floor along the river’s edge with PIT-tag detectors looking for tags in predator scat. After four months of searching, we ended up at the mouth of the river with not a single tag to show for our efforts. In a last-ditch attempt to find our fish, we crawled below the nests of a nearby heronry and, to much avail, uncovered over 1,200 tags. Herons consumed around 3% of the juvenile salmon in each year of our study, with predation doubling to 6% in a year of low river flow. Salmon predation coincided with chick emergence in the heronries, and accounted for ~10% of the heron diet during chick rearing. Because the impressive nature of heron digestion leaves little trace of their prey, this is the first study to quantify their predation on juvenile salmon.
This presentation will be aired via Zoom Video Conferencing. On the Monday, preceding the event, Nature Vancouver members will receive the Zoom link in the weekly e-News. To join the talk on Thursday, click on that link after 7:15 pm. The talk will begin at 7:30 pm. Non-members are welcome and should email denis@NatureVancouver.ca well in advance to register for the link.