Conservation · Best Practices
Catch-and-Release in Canadian Rivers: Techniques That Improve Survival
Catch-and-release regulations apply to an expanding number of Canadian fisheries. The intent is to allow sport angling while limiting mortality on wild stocks. Whether that intent is achieved depends largely on what happens between the moment a fly is taken and the moment the fish returns to the current.
Brook trout held briefly at the water surface before release, Stoney Brook, New Brunswick. Photo: James Mann / Wikimedia Commons (CC BY 2.0).
Regulatory context: In Canada, catch-and-release requirements are set provincially and federally by species and water body. Requirements may include barbless hooks, specific gear restrictions, and handling prohibitions. Consult Fisheries and Oceans Canada and your provincial regulations before fishing any water managed under catch-and-release rules.
Why Fish Handling Matters
The stress physiology of a caught fish is well-documented in peer-reviewed fisheries literature. When a trout or steelhead is played to exhaustion and handled out of water, it undergoes a cascade of physiological responses: blood lactate rises sharply, blood oxygen falls, and cortisol levels increase significantly. These changes are not immediately reversible. Even a fish that swims away strongly after release can succumb to delayed mortality hours or days later if the handling event was severe enough.
Factors that influence survival after release include: water temperature at the time of capture, duration of the fight, time out of water, physical damage to the fish, and the depth from which the fish was retrieved. Anglers who understand these factors can make decisions that reduce harm without ceasing to fish.
Water Temperature Thresholds
Water temperature is the single most significant predictor of catch-and-release survival in Canadian trout and salmon fisheries. As water temperature rises, dissolved oxygen decreases and the metabolic cost of a fight increases. Fisheries biologists working with BC and federal agencies have identified temperature ranges above which voluntary restraint — or regulatory prohibition — significantly reduces fish mortality.
For steelhead and interior rainbow trout, temperatures above approximately 18°C (64°F) substantially increase stress responses. Above 20°C (68°F), the risk of delayed mortality becomes considerable even with optimal handling. Many anglers and some provincial advisories recommend stopping fishing for cold-water salmonids when river temperatures exceed 18°C during the fishing day.
For Atlantic salmon in Quebec and New Brunswick, similar thresholds apply. The DFO has published guidance on temperature-based voluntary closures for some managed salmon rivers.
Temperature Reference Points
Below 15°C: Optimal conditions for catch-and-release. Fish recover well with standard good-practice handling.
15–18°C: Elevated stress; minimize fight time and handling. Keep fish submerged during hook removal.
18–20°C: High stress; consider stopping fishing or targeting different species. If fish are caught, release immediately with minimal handling.
Above 20°C: Significant mortality risk. DFO and conservation organizations recommend voluntary stoppage on sensitive cold-water fisheries.
Fight Duration
Prolonged fights increase lactic acid accumulation and oxygen debt in fish muscle tissue. The practical guidance from fisheries research is to land fish as quickly as gear allows. This is not always compatible with the pleasures of light-tippet fishing on large fish, but it represents the most significant variable an angler can control.
On large rivers like the Thompson or Miramichi, where steelhead and Atlantic salmon may run substantial distances after being hooked, this is particularly relevant. The distance a fish runs and the current it fights are partly outside the angler's control, but keeping steady pressure and not allowing extended rest periods for the fish shortens overall fight time.
Keeping Fish in the Water
The most consistent improvement an angler can make to their catch-and-release practice is to keep fish submerged throughout the hook removal and release process. Air exposure removes the protective mucus layer, causes the gill filaments to dry, and adds the weight of the fish on its internal organs — stresses that do not occur underwater.
Several Canadian provincial regulations now require or strongly encourage no-air-exposure handling for specific species. British Columbia's current steelhead regulations specify keeping fish in the water; similar language appears in some eastern provincial salmon advisories.
Practical steps:
- Release the fly while the fish is still in a fully submerged position if possible.
- If photography is desired, position the fish at the water surface, lift briefly, shoot, and return immediately — ideally within a few seconds total air exposure time.
- Use forceps or hemostats rather than fingers to remove barbless hooks; this is faster and less damaging.
- Do not grip fish tightly around the midsection; internal organs can be damaged by compression.
Hook and Gear Considerations
Barbless hooks reduce the time required to remove a hook and cause less tissue damage in the process. Many Canadian catch-and-release regulations mandate barbless hooks; even where they do not, pinching the barb flat before fishing is a simple step that meaningfully improves outcomes.
Circle hooks, increasingly used in bait fishing, are not generally applicable to fly fishing but may be relevant in some multi-method fisheries. For fly fishing specifically, the choice of hook gauge and bend geometry affects both how deeply a hook sets and how easily it can be removed without handling the fish excessively.
Monofilament leaders heavier than strictly necessary for the water conditions reduce fight time on large fish. Many experienced steelhead anglers use leaders heavier than needed for fly presentation in order to land fish quickly, particularly in warm water.
Reviving and Releasing
After unhooking, support the fish horizontally in the current. Hold it gently facing upstream in moving water, or facing into a gentle current in a pool. Do not move the fish back and forth — older advice to "pump" a fish to circulate water through the gills has been shown in more recent research to be no more effective than stationary holding, and may cause additional stress.
Release the fish when it actively resists being held, or when it kicks and pushes out of your hands. A fish that tips sideways or cannot maintain equilibrium after an extended holding period may have sustained more significant physiological compromise; giving it additional recovery time in supported, oxygenated water is the appropriate response.
Seasonal and Species-Specific Notes
Spawning Fish
Fish that are on redds or in spawning condition are under substantial physiological stress already. Many provincial and federal advisories discourage targeting fish actively on spawning gravel. British Columbia's regulations explicitly prohibit fishing over or near active redds in some circumstances. Anglers who identify redds — visible gravel areas with attending fish — should avoid wading through or casting to them.
Brook Trout in Quebec and New Brunswick
Speckled trout are somewhat more tolerant of warm water than rainbow trout or Atlantic salmon, but their thermal tolerances vary by population. Lake populations that enter rivers to spawn in autumn are in spawning condition; brook trout holding in cold tributary streams during summer are occupying thermal refugia and should be disturbed as little as possible. Removing fish from these cold-water pools, even briefly, adds to cumulative stress.