BREAKING THE BOTTLENECKS
A PSF initiative seeks to identify the danger zones in the salmon life cycle.
Salmon Steward: Winter 2021
Over this past decade, the abundance of Chinook and Coho salmon and Steelhead trout in the Salish Sea has declined. There is growing consensus that the first year of marine life plays a key role in regulating productivity for juvenile salmon, and that competition, climate change and predation all contribute to poor salmon and Steelhead returns in southern B.C.
Now, the Pacific Salmon Foundation and the British Columbia Conservation Foundation (BCCF) are investigating survival bottlenecks for salmon and Steelhead throughout the Salish Sea.
The four-year project, which is supported by the B.C. Salmon Restoration and Innovation Fund, began in 2020 and aims to provide new information on bottlenecks for Chinook, Coho and Steelhead. The project involves tagging fish with small Passive Integrated Transponder (PIT) tags, which help track the survival of populations.
“Each PIT tag has a unique identification code associated with it that allows us to monitor fish at different life stages – as they migrate out through the freshwater, into the marine environment and then again as they return as adults. We’ll use this information to piece together survival estimates at these different points,” says project co-manager Collin Middleton, a PSF biologist.
In the first year of the project alone, BCCF staff, other partners and volunteer anglers have tagged more than 100,000 fish in hatchery, freshwater and marine environments. Tagging fish in the marine environment is done via micro-trolling, a method developed by our partners at the University of Victoria and BCCF, which involves using specialized miniature trolling equipment to catch juveniles in the ocean.
WHAT EXACTLY IS A BOTTLENECK?
A salmon survival bottleneck is any event (or series of events) that results in a sharp decline in a given population over a relatively short period of time, ultimately limiting future production.
(Photo credit: Danny Swainson) Staff from BCCF and the Ministry of Forests, Lands, Natural Resource Operations and Rural Development add housing to protect connection and communication cables on a PIT system panel in the Englishman River.
PIT antennas and arrays, which passively read tags when tagged individuals swim over or through them, were installed this summer in more than half a dozen priority freshwater areas and hatchery systems in central and eastern Vancouver Island, including: Cowichan River, Nanaimo River, Englishman River, Big Qualicum River, Little Qualicum River, Puntledge River and Quinsam River.
“This project requires building collaborations with a multitude of partners from governments (First Nations, federal and provincial), streamkeeper groups and fishing guides, among others,” says project co-manager Jamieson Atkinson, senior fisheries biologist with BCCF. “I hope this is the start of something big.” With the current partnerships and interest in the program, expansion into the Fraser River, Sunshine Coast and other Vancouver Island systems is not out of the question.
This initiative will also examine the ecology of juveniles during their first ocean winter, monitor recreational fishery catches and predation mortality, and evaluate alternative hatchery strategies as conservation tools for Steelhead.
HOW BIG IS A PIT TAG?
Each tag is about the size of a grain of rice, measuring 12 mm by- 2.5 mm. PIT tags employ the same Radio-Frequency Identification (RFID) technology used to tap bank cards or scan microchipped pets at the veterinarian.
(Photo credit: Danny Swainson) Anesthetized juvenile Chinook are injected with PIT tags at the Nanaimo River Hatchery
The bottlenecks project emerged after an earlier study revealed the importance of critical mortality periods during the early marine period and the first winter of marine life, and the lower survival of hatchery-produced salmon relative to wild fish in the Cowichan River. “The Cowichan study showed that, through early life stages of Chinook, wild fish survived twice as well as their hatchery counterparts,” Atkinson explains. “We know there are differences in survival between hatchery and wild fish in the Cowichan. Now, we’re applying what we learned from this study to other watersheds on Vancouver Island.”
Middleton adds: “It’s important to keep an eye on these systems where there is considerable hatchery production alongside wild and naturally spawning fish, and to try to come up with ways to set up both for success.”
Through the project, PSF and BCCF along with partners will conduct research that helps us better understand the factors affecting the performance of hatchery and wild stocks, and gather data that informs adaptive management of hatchery programs, harvest fisheries, and conservation and sustainability objectives.
Currently, PIT tagging for the bottlenecks project is scheduled to finish in March 2024, with data collection and analyses to begin in the years following, as the final tagged fish return to freshwater ecosystems.
(Photo credit: Danny Swainson) A PIT antenna-array system in the Nanaimo River tracks tagged salmon as they swim by.
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