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Most of us care deeply about the trout we catch and the continue health of the fishery. When releasing trout, we want them to survive, thrive and reproduce. A trout dieing shortly after release, is the worst possible outcome.
Over the years, there has been a lot of controversy over which hook type damages trout the less, and results in the lowest fatality rate once released. There are two main types of hooks used in trout fishing, they are single and treble hook. Less commonly seen are dual hooks. They all come in barb and barbless variations.
Single or treble hooks
A common sentiment, Is that single hooks are the best choice. Their proponents claim they cause less damage and are the quickest to remove. One puncture wound has to be less damaging than three?
Unfortunately, it is not that simple. There have been many studies comparing hook design and trout fatality. To summarize, no hook types is the best for all lure styles and size of fish. What the studies found, single hooks were more likely to be swallowed deep, hooking trout in the gills. While the many points of the treble hooks, caught most trout in the jaws or mouth. A wound to the grills has nearly a 40% fatality rate. Contrast that against a 5% fatality for a trout hooked in the jaw or mouth.
One research project (1) looked at the fatality rate of trophy brook trout caught on Mepps Spinners, Cleo Spoons and Rapalas. Rigged with either treble or single point hooks. In both barbed and barbless variations.
During the first 48 hours, there was a 8.3% fatality rate for trophy size brook trout caught on Mepps Spinner or Cleo Spoon using a treble hooks. While only a 2.4% fatality rate using single hooks.
But, it is not so simple. There was a 0% fatality rate for the 126 trout caught on the Rapalas. Despite using two treble hooks. Why was that the case? The researchers theorized that rapalas wobbled more side to side. Vastly increasing the likelihood of the hooks contacting the jaws. I personally speculate the more hooks the earlier it well pierce making jaw captures the most probable.
Trout were simply more likely to fully engulf the straight swimming lnline spinner.
The researchers also found that “Hooking mortality estimates for trout caught on Mepps or Cleo lures were positively and significantly correlated with size of fish.”. That means, the larger the trout, the greater the chance it would engulf the smaller hardware causing serious damage.
Barbs vs barbless hooks
Barbless hooks are simply easier to remove than hooks with barbs. They also do less flesh damage during removal. These reasons combine for faster release time, and the less time a trout spends out of the water the greater its chance of survival becomes.
Over the years, I have heard some arguments that barbless hooks pierce deeper into the trout. Which can be more damaging than a shallow tear from removing a barb. But I have seen no research or anecdotal experience to support that claim.
Rather than heading out and purchasing barbless hooks, it is nearly as effective to pinch down the barbs with a pair of pliers. A few more trout will shake free, but the improvement in survival rate of released fresh is worthy compensation.
Circle Hooks vs J-Hooks
Circle hooks are specially designed to hook fish in the corner of the mouth, and many anglers have discovered that trout are less likely to escape. A normal hook can just as easily pierce into soft flesh, which can tear during the fight. This is less likely to occur to a hook piercing thought the bony jaw.
Something which is little known, Circle hooks do not need to be super sharp to work. A slightly blunter hook Is less likely to pierce the trouts mouth as it rolls towards the jaw.
While circle hooks are usually the domain of the bait fishermen. Some keen fishermen have started to use them on lures. Feedback has been positive. Many require the use of double split rings to get the hook to run straight.
Trout Fatality increases with warmer water.
Studies also show, that released brook trout are more likely to survive, when water temperatures are low. Badly hooked Brook trout have a much higher chance of survival with water temperatures below 14c. This is probably due to a combination of higher oxygen levels, and lower fish metabolism due to the cooler temperatures.
Cut the line or remove swallowed hooks?
Trout have the best chance of survival if the line is cut. Most trout die within 24 hours of a hook being removed. Trout have approximately a 70% chance of survival if the line is cut, and the majority of which will naturally dislodge the hook within the first month.
I have never had a trout swallow a spinner or trout fly, but this could be a real issue faced by bait angler. Is it better to cut the line, or try to remove a swallowed hook? I spent several hours researching this topic. In most cases, it is better to cut the line then it is to attempt to remove a swallowed hook.
An interesting experiment (2) was done with 400 hatchery raised Rainbow trout. These small rainbows were all allowed to swallow the hooks. 200 had the hook manually removed, 177 of which died within the first day. Only 23 survived the four months of the experiment.
An additional 200 rainbow trout, had the hook left inside. Out of which 69 died, but 131 survived and were putting on weight at a similar rate to the control group. The 100 trout strong control group had no fatalities.
These 131 surviving trout were autopsied. 76 of which were able to naturally expel the hook. Loose Hooks or hook parts were found within the stomach of a further 39 fish. The remaining trout had hooks either piercing the stomach wall or elsewhere in the fish.
The results speak for themselves. Trout have a much better chance of survival if a swallowed hook is left to past naturally. If you plan on releasing a trout, do not attempt to remove a swallowed hook.
There was also a study which looked at swallowed hooks on Bluegills. The study compares three groups of Bluegills over 10 days. Bluegills which had swallowed a hook and had the hook remove, Bluegills which had swallowed a hook and had the line cut, and finally a control group.
Removing the hook had a 44% fatality rate after ten days contrast with 12.5% in the group with the cut line. 71.4% of the bluegills were able to expel the hook within the 10 days of the study. This shows fish can dislodge swallowed hooks.
If fishing for the table, treble hooks land approximately quarter more strikes.
For catch and release, for smaller trout. Use a single hook inline spinner or spoon. Spoons offer slightly slower morality rates than inline spinners.
Rapalas with double treble hooks have low fatality rates for all fish sizes. They are the best choice for targeting trophy size trout over 30cm. Due to increased foul hooking, not really recommended for smaller trout.
Trout which are hooked in the gills, or are badly bleeding have a low survival rate in warm temperatures.
Think twice before fishing in warm water conditions. Trout survival rate is a lot lower.
Only fish bait, if you are planning to keep the trout. If a you need to release swallows the hook cut the line rather than attempting to remove the hook.
1) : Andrew J. Nuhfer & Gaylord R. Alexander (1992) Hooking Mortality of Trophy-Sized Wild Brook Trout Caught on Artificial Lures, North American Journal of Fisheries Management, 12:3, 634-644, DOI: 10.1577/1548-8675(1992)012<0634:HMOTSW>2.3.CO;2
2) John W. Mason & Robert L. Hunt (1967) Mortality Rates of Deeply Hooked Rainbow Trout, The Progressive Fish-Culturist, 29:2, 87-91, DOI: 10.1577/1548-8640(1967)29[87:MRODHR]2.0.CO;2
3) Fobert, E., Meining, P., Colotelo, A., O’Connor, C., & Cooke, S. J. (2009). Cut the line or remove the hook? An evaluation of sublethal and lethal endpoints for deeply hooked bluegill. Fisheries Research, 99(1), 38–46. doi:10.1016/j.fishres.2009.04.006