Can anyone explain hooking mortality?

[Bureaucrat]

Given the topic of catch and release has come up, it got me to wondering about hooking mortality. I've never heard it mentioned anywhere other than in Mille Lacs stuff. Can anyone explain the concept of hooking mortality to me? Is it just that Mille Lacs walleyes die from hook punctures or what's the deal?

[ZachD]

After being caught and released by an angler, fish may die for a variety of reasons. The most common causes of death are the physiological stresses caused by the struggle during capture and injuries caused by the hook or the angler. Some fish may die even though they appear unharmed and despite efforts at revival. Fish that struggle intensely for a long time during capture are usually exhausted and stressed from the accumulation of excessive amounts of lactic acid in their muscles and blood. Severe exhaustion causes physiological imbalance, muscle failure, or death. Therefore, use the proper weight-class tackle; land your catch quickly, and when possible, leave the fish in the water while you release it. Any exhausted animal needs oxygen to recover!

Hook wounds may appear minor to anglers, but damage to the gills, eyes, or internal organs can be fatal. If the fish is hooked deep in the throat or gut, research shows that it is best to cut the leader at the hook and leave the hook in the fish. Prolonged attempts to remove the hook often do more harm than good. In the Fish and Wildlife Research Institute's (FWRI)* study of release mortality in snook, 24 snook were deep hooked. We removed the hooks from 12 snook, and we left the hook intact and cut the leader in the other 12 snook. We found that four of the 12 deep-hooked snook died after the hooks were removed. None died when we simply cut the leader and left the hook alone. Fish are capable of rejecting, expelling, or encapsulating hooks. Encapsulation is a process whereby the fishes' healing process causes the hook to be covered with an inert matrix of calcified material; or a-cellular tissue. Steel and bronze hooks are less toxic and are rejected or "dissolved" sooner than are stainless steel and cadmium-plated or nickel-plated hooks.

Two types of hooks, barbless and circle hooks, are known to reduce injury and mortality of released fishes. Barbless hooks reduce tissue damage and handling stress because they can be removed quickly and easily. Barbless hooks are popular in the freshwater trout fisheries and are becoming increasingly popular with saltwater anglers. A Florida study conducted on snappers and groupers demonstrated that catch rates are the same for barbed and barbless hooks. If barbless hooks are not available, simply use pliers to crimp or remove the barbs from regular hooks. A caveat is called for when using these types of hooks: after having hooked your quarry, don't give the fish any slack, because it will be more likely to escape from barbless hooks than from regular hooks.

The use of circle hooks has been researched and compared to regular hooks-often called "J" hooks-in several fisheries. In all of them except in the flatfish, or flounder, fishery, circle hooks were shown to result in significantly lower hooking mortality and higher catch rates. In one study, tunas and billfishes were hooked in the jaw 90% of the time. Circle hooks reduced deep hooking fourfold in the striped bass fishery while "J" hooks were 21 times more likely to cause a bleeding injury. Circle hooks are a bit more tedious to use, especially with live bait, but the advantages should compel anglers to give them an honest trial. Overall, research shows that circle hooks improve catch rates and reduce hooking mortality which results in positive impacts on exploited fish stocks.

Studies on striped bass, spotted seatrout, and snook have shown that live bait was used in most cases of hook-related mortality and that "gut hooking" was the primary cause of death. Artificial lures are generally in motion, so the fish takes the bait and the hook is set before the lure can be swallowed. To avoid internal damage from gut hooking, when you use live or dead bait try to set the hook immediately; with natural bait, there is less motion-the fishes' immediate reaction is to swallow the bait. If you allow the fish to run with the bait, the chances of gut hooking the fish increase.

Survival rates for some Florida fishes

Controlled studies have shown that most fish released after hook-and-line capture, survive. Researchers working in Boca Grande Pass tagged 27 tarpon with sonic transmitters and found that 26 of these hook-and-line-caught fish survived. The one fish that died had been lifted from the water for a prerelease photograph. Scientists repeatedly caught bonefish held in a large pond in the Florida Keys and found that 96% survived capture. A few of the bonefish that ultimately died had been caught five to ten times each, which suggests that bonefish hooked and released in the wild probably have an even higher survival rate. Angler-caught snook held in large net-pens throughout Florida had a 98% survival rate. Most of the snook that died were caught with live bait, consistent with studies showing that fish caught with lures generally survive. Spotted seatrout caught in Tampa Bay had a 95% survival rate. Hook position affected survival rates; trout hooked in the gills or gut had lower survival rates than those hooked in the mouth. Redfish survival rates range from 84% in Georgia waters to 96% in Texas waters. Like seatrout, hook position affected survival rates; more than 50% of the throat or gut hooked fish died. These studies demonstrate that catch-and-release-fishing works-most fish that are released survive. By following a few simple guidelines, anglers can maximize survival rates.

[ZachD]

And Bringing them up from deep water make them blow up

[leech~~]

It can happen on any lake. Fish can be hooked deep, have their gills ripped, pulled up from to deep to fast, or just stressed out from the fight and not make it once released.

[CANOPY SAM]

Bureaucrat.

More often then just trauma to the fish via hooks doing damage, it's the rapid change in pressure and temperature that kills many fish.

Fish pulled from deeper water have acclimated to much higher barometric pressure below that much water. When quickly pulled to the surface the pressure change is dramatic, and they nearly explode from the inside out. Hence, the picture you see above.

A fish's eyes will bulge out, and it's swim bladder (an internal organ that regulates it's buoyancy) will expand and often extrude from it's oral cavity.

Also, particularly during the hot summer months, but also throughout much of the year, minus the "turn-over", temperature levels in lakes are quite markedly stratified. Meaning there are fairly clear gradients from colder to warmer water throughout the entire water column.

As colder water is heavier then warmer water, naturally the colder water is at the deepest points in the lake, and the warmest water is at or near the surface. Fish that primarily inhabit colder deeper water again have acclimated to this environment, and many of these species are VERY intolerant of a sudden temperature change. So again, when quickly pulled from this cold water near the bottom, to the warm water on the surface, the rapid temperature change is simply too much for their system, and they are shocked into submission.

[CANOPY SAM]

I'm just guessing here, but perhaps your question in this regard, pointed toward Upper Red Lake, is generally about why isn't this an issue on Upper Red?

If so, the answer is fairly simple. Upper Red Lake is, for the most part, a very shallow bowl. Most of the water, at least the water we are allowed to fish on this lake, is quite shallow (15 feet at the deepest end?). So the temperature/barometric pressure gradients during the summer are not so profound as one might find in lakes with much deeper water, and more structure.

So when we're pulling fish out of 4-12 feet of water on Upper Red Lake, even in the summer time, the temp/pressure shock isn't nearly so bad as you might find in Mille Lacs or Lake of the Woods, where fish might be coming from much deeper water at the same time of year.

So overall catch and release mortality is likely much lower on Upper Red Lake in general when compared to other lakes like Mille Lacs or Lake of the Woods. That's not to say it doesn't happen. For many of the reasons stated earlier, related primarily to mechanical trauma via hooks, there are fish that are released and die in Upper Red as well. I see quite a few "floaters" on Upper Red during the summer. But I think overall the catch and release mortality is lower then other lakes.

Hope this addresses your question?

[aanderud]

Here's a short snippet from a study that was done on Rainy Lake a few years ago. Depths like Upper Red has (mostly under 15 feet) aren't much of a problem, but as you get over 30 feet deep it becomes and issue quickly as this deep-water study shows:

[bturck]

good info in above posts. something that has aways blown me away is the countless fishing programs where fish are being handled , for the proverbial pictures or videos, with hands and fingers totally inserted into the fishes gills. these pictures show the gill plates totally distended. now that certainly can't be in the best intertest of catch and release without doing damage to the fish. just sayin

[Bureaucrat]

That makes sense. I've just never seen it discussed anywhere other than on Mille Lacs.

[ZachD]

I think the reason why we hear so much of the hooking mortality on lacs is because all of the controversy that surrounds how many pounds of fish we can take annually. When they figure the numbers they have to account for it. I have heard a lot of arguments on that we should be able to keep more because they could die any way blah blah. You don't hear about it on many other lakes because they are not putting a slot and limits like they do on lacs. Lake of the woods you don't hear it because fishing is good and most people care less if that lake ever went to the dumps I would think it would be brought up as well.