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. Damage by hooks, exhaustion, and sometimes excessive pressure when the fish is brought to the surface, all contribute to loss of life. However, the mere trauma of capture, even for short periods, can herald death.
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
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.
TOURNAMENTS - GREAT TOLL ON FISH LIVES
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.
FISH TAKEN FROM DEEPER WATERS IN GREAT DANGER
The depth of water that fish are taken from also affects their chance of death. One 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.
TEMPERATURE AFFECTS DEATH RATE
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.
EVEN BRIEF AIR EXPOSURE HAS IMPACT ON
SURVIVAL DURING NEXT 12 HOURS
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.
HOOKS AND THEIR DAMAGE
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%.
EXHAUSTION DECREASES CHANCE OF LIVING
Scientists (Julie, 2002) found that fish often struggle to complete exhaustion. This can result in severe physiological disturbances, and a significant percentage may die.
TAGGING ENDANGERS FISH
Often anglers feel that they are doing some sort of good deed by tagging fish they release. However, American scientists (Julie, 2002) have found that striped bass that were tagged, increased their chances of dying by one sixth.