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Science of Live Release


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Research carried out both in North America and Europe shows that wild Atlantic salmon angled, and then PROPERLY released will recover successfully in a short time and go on to spawn successfully.

The most critical factor is the expertise anglers develop in releasing Atlantic salmon. Wild salmon angled are exerting themselves to an exhausted state in the same way a marathon runner might.

The fish needs oxygen in order to recover. Keep the fish in the water so it can continue to breathe and recover with the oxygen-bearing water flowing over the gills.

In the 21st century it is important for anglers to release grilse as well as large salmon.
Read more.


From Dr. Bruce Tufts of Canada's Queen's University on live release:

"...The practices of individual anglers are important in determing the magnitude of the post-angling disturbance. Minimizing air exposure of fish is very important. Under conditions where the likelihood of delayed mortality is increased (eg. elevated temperatures), additional stresses such as air exposure may be critical in determining the fate of angled salmon."

Live Release - Here are some scientific papers to read on the subject:
  1. Study of Live Release on the Conne River, Newfoundland - Dempson, Furey & Bloom
  2. Implications of catch-and-release angling on Atlantic salmon - Tufts, Davidson & Bielak
  3. Catch-and-Release evaluation on the Ponoi - Whoriskey, Prusov & Crabbe
  4. Ponoi Mark and Recapture Study - Prusov, Whoriskey & Crabbe

Some Samples of the Research

2003 Release of Research Results from the Spey River, in UK

The Catch and Release Tagging Project concluded in 2002 with 386 spring salmon (Feb.-May) and 473 summer salmon and grilse (June-Sept.) tagged and released. Recaptures of spring salmon varied, from 16% in 2000, to 7% in 2001 and 11% in 2002, with an average recapture rate of 10%.

Only two summer salmon were recaptured (0.4%). Recapture rates are highest for February fish, with 30% of fish caught again. However, recapture rates decline as the season progresses, with only 3% of June fish caught a second time. These figures may well reflect the actual exploitation rates of fish entering the river at different times of the year. When analysed in more detail it is evident that among spring salmon, fish caught and released in February-March can be recaptured until May,and fish caught in April-May are vulnerable until July.

Many spring fish can also be recaptured in September when the spawning season approaches. These findings confirm that spring salmon are particularly vulnerable to capture by anglers. Released fish were recaptured in every month except August, and therefore require measures to protect them beyond the spring period. These results underpin the SFB's Salmon Conservation Policy for 2003, which aims to protect spring salmon throuthout the season.

The project also contributed significant numbers of extra eggs laid in the river. Of the 386 spring salmon that were recaptured 368 were re-released to spawn. Approximately 70% of these were female with an average weight 9lbs. Knowing that Spey salmon stripped at the Sandbank Hatchery produce 700 eggs per lb these returned springers contributed 1.6 million additional naturally-spawned eggs in 2000-2002. Assuming a 50:50 sex ratio for summer salmon and grilse and an average weight of 10lbs, the 471 tagged fish re-released provided a further 1.6 million eggs.

The tagging experiment was carried out on ten fishing beats, and partly due to the success of the project and a growing acceptance of catch and release, many other beats also released salmon further boosting the numbers of extra eggs laid in the river.

25 Years of Studies on Live Release

Over the past 25 years research has been conducted on many rivers on both sides of the Atlantic showing that Atlantic salmon survive after release when properly handled by anglers.

  • In Iceland a three year study in the late 1970s saw 42 angled salmon tagged and released. Fifteen per cent were angled a second time. One hundred per cent survival of caught and released salmon was observed.
  • Between 1982 and 1984, a study on North Pole Brook, a tributary of the Little Southwest Miramichi in New Brunswick, found in the latter two years no mortality among the caught and released salmon. In the first year a 3 per cent mortality was related to fish being hooked in eyes or gills only.
  • The Ponoi: As part of a multi-year program of research and management in northwestern Russia on the Ponoi River, ASF's Dr.Fred Whoriskey carried out research in which 62 angled fish were penned for 24 hours, and only a single fish died. They were then released with radio transmitters and most were followed until the end of the fishing season. Two of the fish were caught a second time, and were successfully released.
  • It is worthwhile noting that only a single mortality occurred even with the increased stresses of having a transmitter inserted into their bodies.

During the 1990s Dr. Bruce Tufts of Queens University, Kingston, Ontario, along with several associates, undertook a number of research projects.

The many studies showed low or zero mortality in most conditions, when the wild Atlantic salmon were carefully handled and kept in the water. It was very evident, however, that when water temperatures were above 20 C/ 68 F it was vitally important to keep the Atlantic salmon in the water, and to reduce stresses on the fish to the absolute minimum.

Many of the research projects involved wild salmon being equipped with visual or radio tags. In one study 15 angled grilse (1 Sea-winter salmon) on the Upsalquitch River of New Brunswick were visually tagged with Carlin tags. They were released back into the river, and 100% survival in the clear waters of the river was observed. Ten fish were equipped with radio tags, and nine were found several days after being angled on the same river.

Dr. Bruce Tufts' work also included muscle analysis of caught & released wild Atlantic salmon. In late fall he discovered that after angling, muscle pH and lactate levels, signs of the exertions of the wild salmon, returned to normal within 2 to 4 hours - more rapidly than that observed in other species such as wild rainbow trout.

One research project involved the assessment of differences in the egg survival between angled and non-angled wild salmon. This involved the added stress of containment and transport of these Atlantic salmon to a hatchery. Among 20 Atlantic salmon caught and transported to the hatchery for study, there was ZERO mortality.

Even more interestingly, ninety-eight per cent of the angled fish eggs survived, vs. 97 per cent of eggs from non-angled salmon. Thus Live Release did not impact the spawning success of the fish.

Dr. Tufts concludes the following from the experiment on autumn fish, "Our results indicate that the likelihood of delayed mortality is minimal and there are probably no significant consequences on gamete viability following angling and release of Atlantic salmon in the late fall."

Kelts, Atlantic salmon that have already spawned, were studied by Dr. Tufts group in the Margaree River of Nova Scotia for two successive spring seasons. Mortality was ZERO out of 26 in one season, and 1 out of 83 in the other season, the single mortality being due to hooking the gills. That translates into a Live release mortality of less than ONE per cent for the study.

Air Exposure: For wild Atlantic salmon, even brief air exposure of 1 minute after the exertion of being angled increased the changes seen in their physiology. But if air exposure of the gills is kept to a minimum, the Atlantic salmon survived, Tufts notes.

In summer, the research has shown that anglers need to be especially sensitive to the needs of the wild salmon, not angling the fish to exhaustion, nor taking it out of the water for more than a few seconds. But even in summer conditions, properly handled Atlantic salmon will recover.

Overall, Dr. Bruce Tufts concludes:

"Our results indicate that most Atlantic salmon do survive being caught and released. Regardless of the conditions, the majority of the salmon that were exhaustively exercised or angled in each of our studies survived. These findings are probably not surprising since this species is already highly adapted to cope with periods of exhaustive exercise during its arduous spawning migrations."

In Scotland, the Dee has had a large Live Release program for five years. Researcher John Webb, Research Biologist of the Atlantic Salmon Trust, radio tagged salmon, which were subsequently recovered. There was 100 per cent survival more than two months after the tagging.


If an angler learns proper techniques of Live Release, and keeps the Atlantic salmon in the water, the fish will almost always survive.

Associated File: The Case for Releasing Grilse
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