Nerd Nite v. 49: Waterslides, Oil Tankers, and Predator-Prey Relationships

When you were young, did you spend your summers zooming down waterslides? We remember days where our calves ached from climbing stairs, and sore bums from well… you know. And, if you were like us, you also stared at those slides and thought “How are these things made? And, is it going to disassemble while I’m on it?”. Today, we spend more of our summer days staring out at the oil tankers lining the shore, or watching seagulls dive down to retrieve waste left behind by tourists on Granville Island, but we maintain that curiousity about the things around us! So, splash into a New Year with us to learn about all three: waterslides, oil tankers, and predator-prey relationships.

Hosted by: Kaylee Byers and Michael Unger

Where: The Fox Cabaret

When: Wednesday January 22nd; Doors @ 7, show starts @ 7:30

Tickets: Eventbrite

Poster by: Armin Mortazavi

Music by: DJ Burger

1. Ecology

Zachary Sherker 

An array of opportunistic foragers (e.g. brown trout, Caspian terns, double-crested cormorants, common mergansers, river otters, mink, Pacific harbour seals) are suspected of preying on salmon smolts in rivers and estuaries during their outmigration from natal streams. These predators may account, in part, for the poor survival to adulthood in Salish Sea salmon populations. However, there is another piscivore predator that has been left off the list of usual suspects-the Pacific great blue heron. We investigated the role that herons may be playing in the decline of salmon by estimating rates of mortality caused by herons on wild and hatchery-reared smolts implanted with PIT tags in the Cowichan River, Big Qualicum River, and Capilano River from 2008-2018. We scanned under the nests at local heron rookeries (within 35 km of the river systems) using a Biomark IS1001 mobile array and recovered over 1,200 smolt tags in fecal remains under the nests, representing annual minimum predation estimates of 1-3% in all rivers. The distribution and timing of tag depositions under the nests indicated that most herons take part in salmon smolt predation and that consumption takes place during the chick-rearing phase of the breeding season. Predation occurred primarily in the lower river or upper estuary and was highest in years of critically low river flow. Smaller salmon smolts were significantly more susceptible to heron predation in all systems and predation rates were comparable between wild and hatchery-reared smolts. Recovering so many tags at heron rookeries was not expected and indicates that blue herons are a major predator of wild and hatchery-reared juvenile salmon. The location of heron rookeries relative to salmon bearing rivers is likely a good predictor of the impact on local salmon runs, and a potential means to assess coast-wide effects of great blue herons on salmon recovery.

Bio: Zachary is completing an MSc at UBC investigating freshwater and estuarine predation on juvenile salmon during their out-migration from natal rivers and works as a part-time contract biologist in the lower mainland. Prior to coming out west, Zach completed an interdisciplinary BSc in Aquatic Resources and Biology at St. F.X. University in Antigonish, N.S. During his undergraduate degree, Zach ran field and lab experiments to explore predator-induced phenotypic plasticity in intertidal blue mussels exposed to the waterborne cues of a drilling predator snail. He also conducted biological surveys on lobster fishing boats and worked as a fisheries observer for the offshore commercial snow crab fleet.

2. Waterslides

Shane Jensen