Repost: Fishing Muskies in Warm Water Conditions - The Outdoor Community
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Repost: Fishing Muskies in Warm Water Conditions

I forgot the rules here and posted originally with a link to my web site. The rules state you can't have links to other outdoor sites. So, I will repost this helpful info with as much text from that helpful link here, w/o the link. I will also post the replies at the bottom.

Condition Considerations

There are certain fishing conditions that require special precautions to be taken, or that extra care be given to the fish in order to reduce overstressing muskies, and help minimize the occurence of delayed mortality.

Muskies fishermen release the majority of the fish that they catch. Because of this, there are certain steps we should be taking to ensure that we're releasing fish healthy, and in good condition. Taking special precautions in various fishing situations can greatly increase the survival rate of the muskies we release back into the lake.

Two of the main topics summarized here are lactic acidosis, a buildup of lactic acid that can cause abnormal heart rhythms (potentially leading to a sudden stoppage of the heart), and hypoxemia, which is a condition of an abnormally low blood oxygen level. These two issues account for a significant portion of the delayed mortality following the catch & release process.

Fishermen can have some control over these issues by simply being more aware of their effects on Muskies, and by changing some of the ways in which we fish for them.

Lactic Acid is a natural by-product of functioning muscle tissue. When fish have normal blood oxygen levels, their muscles can function aerobically with very little lactic acid produced. When the supply of oxygen in their blood is depleted, more and more lactic acid is produced and they may experience numerous metabolic abnormalities. This condition is further worsened by the hypoxemia resulting from a prolonged fight in water low in dissolved oxygen, or from long periods of air exposure while the fish is handled and photographed.

Hypoxia means low oxygen, and refers here to a fish’s lack of obtaining adequate oxygen. This lack of oxygen causes their pH level to decrease and they become more acidic. That in turn leads to the interference of oxygen getting delivered to the tissues, such as the heart. As the heart becomes hypoxemic, it becomes more susceptible to abnormal rhythms. In periods of pronounced hypoxemia, the heart may even cease to function normally, possibly resulting in the death of the fish.
Many Muskie fishermen believe in using stout tackle and fighting the fish quickly without over-stressing the animal. When fighting a fish on the line, lactic acid begins to build in their muscle tissue. The longer the fight lasts, the higher the level of lactic acid produced. Once the level of lactic acid reaches the “point of no return”, it may cause the fish to die. They may swim away at the time they’re released, but can often die many hours later.

Higher water temperatures can magnify the oxygen and pH imbalance in the fish, and this increases the importance of shortening the fight. To reduce lactic acid levels and restore the normal pH of the blood, exhausted fish need oxygen fast, and the only way to get oxygen to the fish quickly is by allowing water to flow through its gills. Therefore many fishermen are now choosing to simply unhook the fish in the net, to avoid handling them at all. Unhooking and releasing Muskies in a timely manner will allow them to recover much sooner, and could mean the difference between life and death for the fish.

As most anglers know, water temperature is the main factor in determining how much oxygen is available to the fish. Because warm water isn’t capable of holding as much dissolved oxygen as cold water, lakes with low oxygen levels can also increase the occurrence of hypoxemia in angled fish, potentially increasing delayed mortality. Many serious Muskie fishermen will not fish for Muskies at all once the water reaches certain temperatures, such as 80 degrees. In the warm summer months when water temperatures are highest, many Muskie anglers choose to pursue other species of fish that are less sensitive than Muskies to the effects of low dissolved oxygen levels.

Fishing in high winds can also increase the risk of delayed mortality, especially if you’re fishing alone. It may be quite difficult to control the boat while playing the fish, which can prolong the fight time and increase the occurrence of lactic acidosis. Concurrently, if the water temperature is high, the fish may also become hypoxemic. Fishermen should strongly consider whether they should fish these locations in these scenarios or choose a different approach.

As Muskie fishermen, we have a great deal of control over many of the factors affecting delayed mortality, simply by limiting the amount of time we keep a fish out of the water. While the incidence of delayed mortality has been estimated to be in the range of 5-30% the exact figure can never be known, as there are many determining factors. Therefore we recommend that every effort be made to keep delayed mortality deaths to a minimum.

There are many other situations that also require taking precautions to help minimize the risk of delayed mortality, such as targeting deep-water fish. To achieve neutral buoyancy and have the ability to stay at any depth it may want to, a Muskie has to be able to take gas into the bladder and let gas out of it. When fish are rapidly brought to the surface from deep water, they may experience a rupture of the swim bladder, possibly allowing a gas bubble to enter the bloodstream. This gas bubble could then find its way to the gills, brain, (or other vital organ) and thus block vital blood flow from the downstream tissue. This type of injury is similar to that seen in humans who rapidly ascend from deep water. In addition, if the fish is caught from water deeper than about 50 feet, it may experience decompression sickness, (the bends), just like humans do. Due to these concerns, it has been suggested that Muskie fishermen avoid pursuing deep-water fish if they intend to release them.

Certain care should also be taken to ensure the release of healthy fish when fishing at night. In many instances the water temperature will be more beneficial to the well being of the fish in the cooler evening hours, but there are other issues that come up. You’ll want to make sure you’re aware of the location of your release tools and also minimize the amount of time the fish is in the net.

Cold air temperatures may also have a slight effect on the Muskie. When taken from the water in very cold air temperatures, there is a risk of freezing to the fish’s eyes and/or gills. Some consider it to be a concern, but at this point it doesn’t seem to be quite as big of an issue as the others mentioned here.

As much as we enjoy fishing for Muskies, there are times throughout the year when it can prove detrimental to their survival for us to fish for them without first considering the scenarios we’re faced with that particular day. If certain steps are taken, we can ensure that Muskies will survive and prosper for the next generation of fishermen.

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Other posts from original thread:

Thanks for posting this info Ed, it is definitely a good resource for people who are considering getting into musky fishing, or for those who just want to give the fish they release the best chance at survival. I like the section discussing the adverse conditions and the problems that can occur. My first thought when I read it was "I have fished under all of these conditions, so does that make me a bad guy?" I don't think I am. But I think the intent of the article is to help people understand some of the high risk situations, and then be better prepared to deal with them, or avoid them altogether.
Thanks for the good words, FishDoctor!
Thanks for that Ed, I will check it out, as My boys wanted to go out and fish for Muskies. I've caught a few in the fall and early spring, but had no idea of the dangers of catching them in the summer months. Thanks.
Thanks for posting. Good information to assist folks in making their decisions.
Awesome Post ED!!! Thanks
Good read. thanks. I will still be after them this weekend. Hope to hook up on another tiger.
Great info Ed! I would like add some info though. Rivers and lakes are differant monsters in warm water conditions. Disolved oxygen is constant from the bottom to the surface in rivers due to the constantly moving and churning water. Lakes, on the otherhand, have an area at the surface that is dangerously low in oxygen. This layer of low oxygen may only be a few inches or it could be several feet deep. This seems to be the most pronounced when water temps reach and exceed 80 degrees. I hope this helps.
Thanks for the added info, Hawg Chaser.
Not familiar with lake/pond surfaces being devoid of oxygen HG. At least not for extended periods. Always thought surface agitation due to waves/wind was a critical point of oxygen exchange between the atmosphere and water, so the surface would typically be higher in DO than the underlying water. Perhaps the lack of DO at the surface that HG is referring to is caused in part by some other phytoplankton decomposition and/or lack of respiration at night, or maybe on days without wind. Either way I wouldn't expect the effects to be long term.

I have heard of water at depths below a thermocline in lakes lacking DO. In these situations the coolest water in the system can also be the lowest in DO. Probably why fish are often located at or just above the thermocline rather than at significant depths below it.

I think the general thought with the 80F is that warm water is the easiest thing for a fisherman to determine and base his/her decision on.

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