Most anglers believe that the fish that they release swim away unaffected by their encounter. This is not the case.
Many fish will suffer and die, sometimes several hours later. Studies have found that a
third, half, or even more fish can die at a site.
Fish caught at tournaments are at the greatest risk of dying, as they are often repeatedly caught in the same day.
Not all fish survive
“Many recreational anglers practice catch and-release angling, where fish are returned to the water with the presumption that they will survive. However, not all fish survive, and those that do often experience sublethal consequences including injury and stress.” 1
“One of the key components to the increased use of catch-and-release practices, both by anglers and fisheries managers, is the assumption that fish which are released actually survive the experience. This assumption comes from the observation that when fish are released after being caught they generally swim away, apparently unharmed. However, research indicates that most mortality occurs some time after release (Muoneke and Childress, 1994), thus fish that appear healthy upon release may later exhibit injuries or distress caused by catch-and-release practices.”
2. Fish and Wildlife Branch. Ontario Ministry of Natural Resources.
A review of research into fish deaths at the hands of anglers was made by Muoneke and Childress in 1994. They collected data from fisheries management agencies in all American states, from the American government, all Canadian provinces, and a number of academic and research institutions. They found, on many occasions, shockingly high death rates.
Most deaths occurred within 24 hours of the fish’s impalement on a hook. The deaths rates in studies included:
Such carnage also alters population structure and reduces genetic diversity.
Angling tournaments take a greater toll on fish lives. This has been found in a number of studies. Tournaments in South Dakota and Florida killed a quarter of the fish caught, another in Texas killed a third. The fish suffer repeated capture, and so their chances of dying increase.
The depth of water that fish are taken from also affects their chance of death. A study found that a third of rainbow trout died when only taken at 1 to 3 metres, with this rising to half at 6 metres. Three-quarters of black crappies, when caught between 6 and 16 metres died. Eyes of blue rockfish were forced out of their sockets when caught at 76 meters.
Another effect on the death rate is temperature. For example, one study showed that striped bass caught in the spring and summer were more likely to die.
The longer a fish is out of water, the more its life is in danger. Scientists in Canada (Ferguson, 1992) found that when trout were exposed to air for 30 seconds, a third of them went on to die from this. When trout were exposed to air for 60 seconds, this caused three-quarters of them to later die. It may take 12 hours for the fish to die, giving anglers the false impression that released fish always survive. This "delayed mortality" has been found by other scientists. For example, Cooke, 2000, 2000 found that delayed mortality rates were 0 to 77% for largemouth bass and 0 to 47% for smallmouth bass.
Different hooks have been proved to be the cause of different injuries to fish. Single hooks penetrate fish deeper, treble hooks entangle in gills, and barbed hooks on lures impale the oesophagus and gill arches. Fish hooked in vital organs usually die. In a study, scientists found, using different hooks, that nearly half of the salmon that died were hooked in the gut, and a quarter in the oesophagus. The overall death rate was 75%.
Scientists (Julie, 2002) found that fish often struggle to complete exhaustion. This can result in severe physiological disturbances, and a significant percentage may die.
Often anglers feel that they are doing some sort of good deed by tagging fish they release. However, Danish scientists have found that it causes tissue damage, decreased swimming capacity, reduced growth, increased predation, and an increased chance of death.
Just because fish die in silence, does not mean that they do not suffer. Fish may take 20 minutes to die on a warm day, or even longer on a cold one. If it is not acceptable to slaughter a cow by slowly drowning it, why should a fish suffer a similar fate?