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Casselman, S. J. 2005. Catch-and-release angling: a review with guidelines for proper fish handling practices. Fish & Wildlife Branch. Ontario Ministry of Natural Resources. Peterborough, Ontario. 26 p.
Air Exposure
Ferguson and Tufts (1992) found that there were direct effects of air exposure duration on
mortality of rainbow trout. Rainbow trout that were chased for approximately 10 min had a
survival rate of 88%, however this fell to 62% for fish that were subsequently exposed to air for 30 s and survival was only 28% for fish exposed to air for 60 s (Ferguson and Tufts, 1992).
Cooke et al. (2001) examined the effect of handling time on injury and cardiac disturbance of
rock bass. While air exposure did not result in any mortality, bradycardia (decreased heart rate) was observed during air exposure and cardiac output increased after fish were returned to the water. Simulated angling (fish were chased for 30 s) resulted in increased cardiac output and arrhythmia (irregular heartbeat).
Fish that had 30 s of air exposure required 2 h for full cardiac recovery while fish that were exposed to air for 180 s required 4 h to fully recover (Cooke et al., 2001). These studies demonstrate the detrimental effects of air exposure, and highlight the need to reduce handling time and air exposure during catch-and-release.
Recovery Time
In addition to the immediate effect of catch-and-release, fish may not physiologically
recover for some time after being released.
Beggs et al. (1980) found that angled muskellunge required 12 to 18 h to recover from acidosis caused by angling.
Similar recovery periods have been observed for wild Atlantic salmon, which after being exercised for approximately 10 min, were found to have extracellular acidosis which lasted for about 4 h and blood lactate levels which remained significantly elevated for at least 8 h (Tufts et al., 1991).
In a comparison of hatchery and wild rainbow trout, Wydoski et al. (1976) found that hooking induced increased chloride levels in the blood and plasma osmolarity changes which recovered within 8 h (Wydoski et al., 1976).
Cooke et al. (2003a) examined the cardiac response of largemouth bass to simulated angling events and found that approximately 135 minutes were required for cardiac variables to return to pre-exercise levels. The length of time required for fish to recover from catch-and-release practices may help explain why mortality is often delayed until after release.
Size of Fish
Fish size is thought to be related to catch-and-release mortality because larger fish are
more difficult to handle, thus higher mortality may be expected with increased fish size.
In support of this hypothesis Meals and Miranda (1994) found that mortality of tournament-caught largemouth bass was significantly greater (29% vs 9%) in fish greater than 18 inches in length when compared to fish that were between 12 and 14 inches in length.
Similarly, in a metaanalysis of mortality associated with black bass tournaments, Wilde (1998) found a nonsignificant, but positive relationship between fish size and initial mortality. However, the increased mortality observed in larger fish in these studies may be attributed to crowding and increased oxygen consumption while fish are stored in live wells and not to an intrinsic relationship between fish size and mortality.
There are also a several studies which have examined the relationship between fish mortality and size and have not found any significant relationship (Titus and Vanicek, 1988; Schill, 1996).
It is important to note that the studies discussed here have examined mortality and fish size within species and not between species.
Intraspecific studies are difficult to interpret because any observed relationship between fish size and mortality may be attributed to other factors which differ between species, such as feeding behaviour and mouth morphology. However, it may be reasonable to expect that large species, such as muskellunge and pike, may be more susceptible to mortality than smaller species.
These large fish are often played for longer periods of time and handled longer for photographs, this results in a larger physiological disturbance after angling.
Thus special care should be taken when handling large fish to minimize injury and mortality.
Pozdrawiam serdecznie
Jerzy Kowalski
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