Handling Techniques and Survival of Released Muskellunge by Rod Ramsell

The catch and release of harvestable-size muskellunge has been instrumental in perpetuating populations of this highly prized sport fish throughout its range. The importance of this practice is magnified by two basic occurrences that face today’s fisheries managers. First, muskellunge are a low-density predator even in the best of North America’s waters; and second, the targeted angling pressure for this species is higher than is has ever been, and it is increasing at an alarming rate. As the popularity of muskellunge fishing continues to grow, the practice of catch and release will become even more critical in maintaining populations of this magnificent animal.

Unfortunately, in the 20-plus years that I have been involved in the production and management of this fish, one thing that has become painfully obvious to me is that the survival rate of angler caught and released muskellunge is not as high as we all would like to think. During this time period, I have seen Minnesota’s muskellunge resource rise to levels that have generated international attention. As a result, I’ve come to appreciate the significance of a line from one of my favorite movies, "If you build it, they will come." The "they" in this case are muskie anglers of all skill and experience levels, both resident and non-resident. While the growth of this fishery has generated many new recreational and economic opportunities in this state, it has come with a price. I have personally recovered and autopsied hundreds of dead muskellunge and hybrid muskies from the waters in this part of the State. While the recovery of these fish has provided some valuable information, it has also shown the effects of poor handling of fish that have been caught and subsequently released by anglers. In many cases, it was easy to determine exactly where the fish had been held firmly and how the angler’s hands were oriented by the bruising of tissue resulting from pooling of blood from ruptured vascularization and the damage to skeletal structures of the body and gills. A synthesis of some of the injury observations resulting from autopsies of these recovered angling mortalities form the basis for many of the potential handling problems discussed in this article. In one of the state’s muskellunge brood lakes, I had tagged the fish from the earliest stocked year classes and monitored them during their adult life span. While I had the opportunity to handle these fish and collect their gametes for multiple years, one alarming fact has stood out during this time. I have yet to recapture a single tagged fish whose number has been reported as being caught and released by local anglers! While I am a firm believer in the value of catch and release, one can’t help but be concerned as a result of observations such as this.

We all have to keep this practice in perspective. If we turn back the clock to the 1960’s and before, almost every legal size muskellunge that was caught was harvested. The angling mortality rate was virtually 100 percent during those times. Today, many of us can cite examples from our own experiences of angled and released fish that we know have survived and have been caught or seen again. We know that catch and release can work. But, we must also accept that not every released fish survives. Even if catch and release survival is only 10 percent, it is still better than the days that no harvestable size fish were released!

Don’t misunderstand my point here; I’m not saying that today’s survival rates are only 10 percent, when in fact they are significantly higher than that. How high are they? Well, I’m not going to try to come up with a definite number, when in fact the survival rate for released muskellunge hinges on several variables. These variables can differ from lake to lake and geographic area to geographic area. These variables can include seasonal climates, daily weather conditions, the physical properties and characteristics of water (temperature, oxygenation, etc), physical condition of the individual fish, the location and severity of the hooking injury, and the degree of physiological stress that a muskellunge is subjected to. Other important variables that play critical roles in a fish’s survival are the handling techniques, experience, skill, and confidence of each angler who practices the release of their catch. The point that I do want to emphasize is that the survival rate of released muskellunge is not as high as we would like to believe!

How can we improve the survival of the muskellunge that we release? As one who handles hundreds of adult muskellunge every year, both on and off the job, the answer is quite easy: when handling caught fish, the welfare of the fish must come first. That means we, as anglers, have to "check our egos at the dock," and minimize the stress that we subject these fish to. One of the most important ways to do that is for every angler to improve their fish handling methods.

There are dozens of stressors that fish are faced with and endure every day of their lives. Angling is an unnatural stress event that they are subjected to as a result of we, as anglers, partaking in the pursuit of a sport that we enjoy. I would hope that it is intuitively obvious to all muskellunge anglers that the best way to maximize the survival of angled fish that they intend to release is to keep them in the water! Unlike us, fish are unable to utilize oxygen from the air for respiration. They need to be in water to respire dissolved oxygen. When fish are removed from the water, they are unable to breathe and become significantly stressed in much the same way we would be stressed if our heads were submerged under water. With this in mind, it should now be clear to all anglers, regardless of experience level, that the best release practice to maximize your catch’s survival is to keep your fish in the water while it is in your possession. By doing this, you will minimize the recovery time required for that fish to return its body chemistry to equilibrium levels. Also, the gill lamellae on the gill filaments are very fragile tissues. When removed from the water, they tend to collapse and are vulnerable to temperature extremes that can result in the dehydration or freezing of these delicate structures. Damage to these tissues can inhibit a fish’s ability to respire efficiently upon release. To avoid injury to these structures, an angler’s conquest can still be documented by taking a photo of the fish in the water as it being released. If you want to impress the better muskie anglers in this world, show them a good photo of a water release!

If you haven’t graduated to the level of total water release yet and still need to hold that fish up to impress your friends, then you should at least be conscious of minimizing the time that you have that fish our of water. Remember, you have just subjected that fish to exhaustive exercise while it was on the end of your line. That exhaustive exercise has resulted in an oxygen deficit in its circulatory system. The cells in its body that have been doing all the work to attempt escape are demanding oxygen at increased levels. The only way the fish can get that oxygen is from the water. Get the picture? If you are having trouble visualizing the problem, then let’s try using you as a comparison. Run around the block 3 times, and when crossing the finish line, have your best friend dunk your head under water as you are gasping for breath. How many pictures do you want me to take to commemorate this event for you? The physiological stress that your catch is being subjected to is similar…

If you are angling during the summer months, the recovery of fish subjected to exhaustive exercise is complicated by an inverse physical relationship between water temperature and dissolved oxygen. The higher the water temperature, the less dissolved oxygen water is able to hold in solution. Fish, being cold-blooded animals, have metabolic rates that increase as water temperature increases, thus increasing their demand for dissolved oxygen. Now let’s take these thermally stressed summer fish and examine the effect of the exhaustive exercise it has been subjected to on the end of your line. Your angled fish is now demanding oxygen at an even higher rate than normal, but the warm water has less dissolved oxygen available to that fish for its recovery. The end result is, it will take much longer for that fish to intake the level of dissolved oxygen needed for recovery than it would in cooler water conditions. To put this in perspective in our human example, this would be a similar effect to our runner going around the block three times while on top of Pikes Peak in the Colorado Rockies during the summer. The air available for the runner to recover from exhaustive exercise at that altitude is also greatly reduced, and his recovery time will also be increased significantly. If you take your mid summer fish out of the water, let’s not forget the "head-dunking" that awaits you from our previous example. How many more pictures would you like me to take for you now?

Beyond oxygen deprivation, removing fish from the water can have other hazards for successful release. If your fish must be removed from the water, then its body should be supported as much as possible. It comes from a medium that is denser that the air in which we live. The water medium of a fish’s world provides support for its body. Without that support a fish becomes susceptible to other physiological stressors.

Quite simply, the worst type of out-of-water handling is the vertical hold. A vertical hold exerts a significant amount of stress on the fish’s mechanical physiology.

For the average healthy muskellunge, approximately 5 to12 percent of its weight is in the skull. The remaining 88 to 95 percent of the weight is comprised of the trunk musculature, trunk skeleton, skin, and the viscera. The larger the fish, the higher the percentage of non-skull body weight within that range. This is due to the fact that, at a certain point in their life (approximately 42 inches in length), adult muskellunge tend to increase in size proportionately more in girth than in length.

The primary supportive connection of all this body mass is the muscle and ligament connection of the first cervical vertebrae with the base of the skull. Very little support is provided by the connective tissue on the underside of the head in the vicinity of the isthmus. As a result, a fish held (or hung) vertically has a tremendous amount of gravitational stress upon its mechanical physiology. This can best be seen by the amount of stretch of a fish’s length when it is held vertically. A 39-inch muskellunge, measured laying flat on a measuring board, will measure between 40 and 40.5 inches when held vertically; a 48 inch muskellunge will measure between 50.5 and 51 inches under the same conditions. This increase in length results from the stretching of connective tissues between some of the more anterior vertebrae and the articulation of some of the weakly "hinged" areas and skeletal structures within the skull (see figure A). Using gill net mortalities or recently deceased angling release mortalities that I have recovered, I have demonstrated this physiological effect on Esocids to several student interns and new employees that I have been assigned to train over the years. By showing them this physiological effect first hand, I feel it has helped all of them to become better handlers of the fish they will be working with during their professional careers.

While a brief vertical hold of a muskellunge may not be lethal in all instances, the longer a fish is in this position, the more likely it becomes that damage to the spinal column or its connection to the base of the skull will occur. Muscles in the critical areas will resist the pull of gravity on a fish’s mass briefly, but fatigue quickly causes those muscles to relax and put excessive strain on vulnerable connective tissues. Should a fish struggle or start to shake while in this vertical position, than permanent damage that will result in mortality of that fish becomes virtually guaranteed. The vertical hang is akin to the effects of hanging a "rustler" in the Old West. Whether it was on a gallows or on horseback, once the support for the victim’s body was removed, the end result was the same. If the human body, whose head-to-trunk weight proportions are similar to those of Esocids, can’t take this vertical hanging stress, how can we as sportsmen expect a muskellunge we intend to release to fare any better?

The amount of pull on the muscles and fragile bones of the operculum (gill cover) can also be a concern on vertically held fish. Injury to these mechanical structures can have negative effects on a fish’s ability to feed and respire normally. As mentioned previously, gill lamellae are extremely sensitive structures involved in the acquisition of dissolved oxygen from the water for respiration. When I see an angler with a hand inserted into this delicate area to hold a fish up, it gives me cause for much concern. This area of a fish’s body did not evolve as a "grab handle" for sportsmen. Very few anglers have enough of an understanding of the structure and physiology of this area to go around sticking their "paws" in the gill aperture. If your hands or fingers frequently get scrapped or cut grasping a fish in this area, then guess what…you’re doing it wrong! Some anglers wear a glove to protect their hands from these annoying little nicks. Anybody care to guess what’s wrong with this picture? Yep, you just increased the "bulk" of the hand you are inserting into this area of fragile structures and limited space. I’ve seen many dead muskellunge with damaged gill arches and clubbed and necrotic gill filaments and lamellae as a result of poor handling by their captors.

As far as damage to the internal organs on vertically held fish, this is usually not a life-threatening situation, due to the elasticity of the organ tissues. While the organs may be displaced temporarily by gravity, generally the only damage that is likely to occur internally is the possible tearing of some of the supportive mesentery.

The potential for damage to internal organs becomes more of a consideration on horizontally held fish.

Horizontally held muskellunge have less potential for permanent debilitating or lethal injury-if held properly. Don’t consider this my giving you the "go-ahead" to hold fish this way. It is just a case of the lesser of two evils if a fish absolutely has to be removed from the water for that ego photo. Fish held horizontally and supported improperly will exhibit an oblique change of the natural line of the fish. This is usually evident when one hand has a hold in the head area and the other hand in pressed against the belly of the fish in the area of the pelvic fins. This position leaves a lot of the posterior 30 to 40 percent of the fish’s length unsupported and affected by gravitational pull. The supporting hand in the area of the pelvic fins functions as a fulcrum, with a significant amount of focused pressure exerted at that point. The more horizontal the fish is held, or the longer the duration of such a hold, the greater the potential is for damage to the mechanical physiology of the muskie.

Not only can this result in spinal damage, but damage to internal organs as well.

As mentioned previously, most of the organs are very elastic in nature. However, organs such as the liver, spleen, gall bladder and the swim bladder are more fragile and can be bruised or ruptured as a result of this focused pressure. Elasticity does not imply durability. To illustrate this, let’s use the example of a balloon. If you put focused pressure in one spot in the middle of the balloon, the air inside is displaced to the volume available on either side of the pressure. But if you put enough pressure at that point, there is not enough space for the air to be displaced to-something will eventually give. In a fish, that could be a ruptured swim bladder.

Even before that occurs, there is likely to be internal bruising or hemorrhaging of some of the soft tissues of critical organs. If the fish is held slightly more vertical and rotated such that the supporting hand is more on the fish’s flank, then there is less chance for injury to the internal organs. The point pressure of the supporting hand is against the dense musculature on the side of the fish, rather than against softer viscera. The best way to support the mass of a muskellunge using a horizontal hold is to use your entire supporting arm as a "cradle" (much the same way you would cradle an infant) while the control hand has a grip in the vicinity of the side of the head. Again, this is not my endorsement for you to hold a fish this way, but it is the lesser of the evil options.

In all out-of-water handling options, the loss of the protective mucus layer that protects fish from waterborne bacterial and viral infection is an additional concern. This is especially true during the warmer water temperature months when the populations of these organisms are at their peak. So, if you really want to impress me with a photo of your catch, then minimize your handling and show me that fish in the water!