With funding through the British Columbia Salmon Restoration and Innovation Fund, this reasearch was conducted by the Pacific Salmon Ecology and Conservation Laboratory at the University of British Columbia. PSF co-funded this project to support ways of improving fishing practices for salmon in the recreational sector.
Photos: Steve Johnston and Rod Hsu.
Catch and release – a conservation measure that requires a captured fish to be returned to the water – is a fisheries management practice intended to protect vulnerable salmon stocks.
In the past few decades, the practice has become increasingly common in B.C. as certain salmon stocks have declined and regulations have restricted the size and number of fish that anglers can keep.
Catch and release allows fishing opportunities to continue.
But the downside – which is under increased scrutiny – is that some released fish die, and scientists don’t have all the answers to what is causing mortality, or how many experience post-release mortality.
To evaluate effects of catch and release on Pacific salmon, UBC’s Dr. Scott Hinch led a five-year research project aiming to improve future practices and policies.
“We have to make sure we understand what the consequences are of catch and release so we can improve the practice,” says Dr. Hinch.
A team of graduate students caught and tracked more than 1,500 Chinook and coho salmon in areas frequented by recreational fishers, such as the east coast of Vancouver Island, Barkley Sound, and Juan de Fuca Strait.
Results revealed several factors impact post-release mortality rates, some of which were unexpected. These included hook size and type, air exposure, landing net use, injury level, species, age, and body size.
UBC researchers take a non-invasive gill biopsy from a captured Chinook salmon to study infectious agents.
Injuries sustained during fishing particularly impacted released salmon. Fish with injuries to fins, scales, and eyes had on average up to 20 per cent poorer survival in the 10 days after release compared to fish that were in good physical condition.
Eye injuries, which are related to larger hook sizes, showed a further 20 per cent reduction in survival after 40 days.
“What really surprised me was just how delicate marine salmon are,” says Hinch. “We all know that scales come off these fish when you handle them, but we found the level of scale loss and fin damage caused by landing nets and handling were directly related to their subsequent survival.”
Other findings suggest that coho are less resilient than Chinook to catch and release practices – although more research is needed to determine why.
Hinch and his team have submitted 15 recommendations to Fisheries and Oceans Canada and hope their work can make releasing salmon more fish-friendly.
Among them, they suggest using smaller hook sizes and avoiding gear like treble hooks, tandem hook point set ups, and flashers.
Hinch noted that “anglers should avoid landing nets and keep fish submerged as much as possible during release.”
“There are ways to release fish that will create good survival outcomes,” says Hinch.
A tagged salmon is released back into the water.
UBC’s report proposes 15 recommendations to improve catch and release methods.
Survival at Sea