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Managing Muskies – A goal oriented approach

Category: article

 May 30th, 2007 by OutdoorsFIRST 

Modified May 30th, 2007 at 12:00 AM

We are fortunate that most musky anglers practice catch-and-release fishing these days. Safe to say that over 95% of all legal-size muskellunge caught by anglers targeting muskies are released voluntarily. In general, this is good news and a vast improvement over the days when many muskies were whacked on the head and hauled home for photos and fish bakes. Fishery scientists have learned that muskies approach record size by growing at a moderate rate and living for a long time. Armed with that knowledge, musky fishing leaders have convinced their peers that ‘catch-and-release’ must be practiced if really big fish are desired in waters capable of producing them.Somewhere along the way, however, this catch-and-release approach went a little too far by assuming that releasing all fish of all sizes is always the best strategy for achieving musky population goals. Largemouth bass fishing went through the same phase in the late 1960s and early 1970s. For awhile it was considered sacrilege to keep little largemouth bass. Anglers were told to release them so they could spawn. But then some largemouth bass populations with high recruitment (survival of young to adulthood) started stockpiling large numbers of fish just short of the minimum length limits (usually 12 inches). Growth rates slowed dramatically because of intense competition for suitable-size prey, and few largemouths lived long enough to reach desired sizes. (Most died naturally before attaining 12 inches in length or 6 years of age.)To address this problem in the mid 1970s, Dr. Richard O. Anderson at the University of MissouriColumbia invented slot length limits. Mid-size adult largemouth bass (12 to 15 inches, usually) were protected, while harvest was allowed for larger fish and encouraged for smaller fish. The progressive anglers who pioneered Fishing Facts and In-Fisherman magazines were quick to appreciate this innovative strategy. They began promoting ‘selective harvest’ of sport fish, including small largemouth bass when overabundant. Many bass fisheries improved dramatically. That was decades ago, yet slot limits have not been used to manage muskellunge (or northern pike for that matter) in Wisconsin. The practice of selective harvest in appropriate situations has not yet become part of our musky fishing tradition.So why have we been slow to put slot limits into our bag of tricks for managing muskies? One reason is that fishery management agencies are reluctant to increase complexity in an already complex world without a compelling reason to do so. A bigger reason may be that many anglers and even biologists fear a return to the old days of bonk and bake. But after three decades of experience with slot limits for largemouth bass, I believe we can assume that significant harvest of sub-slot fish, where appropriate, must be actively encouraged or it will not occur. In my opinion, musky anglers and even casual anglers who catch muskies incidentally will not harvest many fish unless actively encouraged to do so. If slot limits fail, it will likely be due to insufficient harvest of old, slow-growing males that dominate some of our musky populations. Some biologists cite this as reason to avoid slot limits, because they believe slots simply will not produce the desired results. They may be right. Everyone realizes that folks are fairly ‘set in their ways’ when it comes to releasing muskies, just like they were with largemouth bass in the 1960s.But before we even consider new strategies such as slot limits for muskellunge, we must have goals. For each fishery in a lake or chain of lakes, we must decide whether we want lots of small fish, a few trophy fish, or something in between. Human nature is to want lots of big fat fish in all waters, but that simply is not possible. We must decide on a system-specific basis whether we want ‘trophy’ fisheries (low catch rates of large fish), ‘action’ fisheries (high catch rates of small fish), or some compromise between the two. Such decisions should not be made by biologists alone. Biologists should inform stakeholders (not just ardent musky anglers) about the potential of each water for natural reproduction and ultimate size attainment by muskellunge. But preference-based decisions about numbers and size should be made in consultation with those who benefit most from the resource. Fishery managers can obtain such information from statewide opinion surveys, on-site creel surveys, and interactive planning sessions with local stakeholders. In the Upper Chippewa Basin, we rely upon all three sources of input.Let’s say our stakeholder-influenced goal for Lake X is a “trophy” fishery. Our specific objectives are for a density of 3 to 4 adult muskies in every 10 acres of water, with 3 to 5 percent of all fish captured in spring fyke nets 50 inches and longer. Lets assume also that the water in question has demonstrated the potential to produce such fish, but that only 1 percent of adults currently exceed 50 inches after several years of management under 40- and 45-inch minimum length limits. In this situation, two types of harvest regulation should be contemplated. If natural recruitment and density are on the low end of the spectrum (1 to 3 adult fish every 10 acres) and growth rate is moderate or fast, a high minimum length limit (probably 50 inches) is appropriate. In such cases we should protect most adults so that some (particularly females) have a chance to attain trophy size. But if recruitment and density are on the high end of the spectrum (7 or more adult fish every 10 acres) and males grow so slowly that they rarely attain a minimum length for harvest, then a slot limit (perhaps 40 to 50 inches protected) may be warranted and some harvest of sub-slot males desirable.On the other end of the spectrum, lets say our stakeholder-influenced goal for Lake Y is an ‘action’ fishery where we can take our children or any novice angler to catch their first musky. Assume that we settled upon specific objectives for a moderately high density of 5 to 7 adult muskies in every 10 acres of water, with 5 to 10 percent of all fish captured in spring fyke nets 38 inches and longer. Lets assume also that this water typically has high natural recruitment and very high adult density (more than 1 adult fish per acre); and less than 1 percent of adult muskellunge exceed the preferred size of 38 inches because there are too many mouths to feed. The existing minimum length limit of 28 inches protects most of the slow-growing males for their entire lives. Mostly females are vulnerable to harvest; but without encouragement, nobody is keeping those either. The only way to reduce excessive density and then modestly improve size structure in such a lake is to generate some harvest of those small, abundant, slow-growing fish (especially the males). And the only way to do that is to impose a slot limit (perhaps a 34- to 40-inch protected length range) and actively encourage the harvest of sub-slot fish while protecting some of the fastest-growing females until some (hopefully 5 to 10 percent of all adults) can attain the preferred size.At this point, folks may be interested to know that Lake X is the Chippewa Flowage, with low to moderate recruitment and a 45-inch minimum length limit currently. And Lake Y is the Tiger Cat Flowage, with excessively high recruitment and a 28-inch minimum length limit currently. The Sawyer County biologist is seriously considering proposing a 50-inch minimum length limit for the Chippewa Flowage and a 34- to 40-inch slot length limit (protected length range) for the Tiger Cat Flowage in order to meet our stakeholder-influenced objectives for both waters. Other Upper Chippewa Basin biologists are considering the 34- to 40-inch slot limit for waters similar to Tiger Cat, where “action” fisheries are valued and desired, but folks want at least a few fish up to 40 inches. And a few lakes (many with 40-inch minimum length limits currently) may be candidates for 40- to 50-inch slot limits. Diverse interests on diverse waters within a county should assure diversity of opportunity for anglers of all types and skill levels.Note that the numbers 34, 40, and 50 are familiar to Wisconsin musky anglers. Many slot limit ranges that do not involve those numbers are possible. For example, we could protect fish 30 to 36 inches long, or 36 to 48 inches long. But my staff and I believe it is important to keep things simple if we can do so without compromising our ability to improve these fisheries. We can work with the numbers 34, 40, and 50 because we find them to be biologically relevant in addition to being easy to remember.Despite our desire for simplicity, we firmly believe there is need for two musky slot limit options in Wisconsin, one low and one high. The “low slot” (34 to 40 inch fish protected) is needed in those situations where adult density is extremely high and there is little expectation of producing trophy-size fish because of habitat and other fish community constraints. Most of the lakes that currently have 28-inch minimum length limits fall into this category. It is counter-productive to keep protecting old, slow-growing 24- to 28-inch males in those waters while allowing even minor harvest of the only fish in those systems (females) capable of achieving more preferred sizes.Justification for a “high slot” (40 to 50 inch fish protected) is more complicated. A high slot may be applicable in waters where recruitment is consistent, growth rate is average or only slightly below average, and density is only moderately high. Many such waters currently are managed under 34-inch or 40-inch minimum length limits. In these waters, the problem is not overpopulation. The problem is an imbalance in the ratio of males to females, resulting in “stockpiling” of males at lengths below existing minimum length limits while allowing at least a few faster-growing females to be harvested. Cannibalism by protected males, even in moderate density, may be sufficient to suppress the survival of new recruits to the population, including females. Ecologists often see a low turnover ratio in cases like this where numerous adults significantly reduce the survival of their own young. It would not be a big problem if male and female muskies grew at the same rate. But selectively harvesting only the fastest-growing fish (mostly females) while protecting almost all the slowest-growing fish (mostly males) results in adult populations increasingly dominated by males that will not allow many new recruits, including females, to enter the adult population. I believe the regulations that enable this problem are inconsistent with goals to create memorable and trophy-size muskellunge. I also believe that a slot limit approach to managing such waters would be more acceptable than high minimum length limits to those who complain of elitism in the musky fishing community and who want novice anglers to have the opportunity to harvest their first fish in some waters.The effectiveness of a “high slot” (40- to 50-inch fish protected) would depend entirely upon the ability of fishery managers to influence the harvest of legal-size, sub-slot fish via public information and voluntary cooperation. Over-harvest seems unlikely in light of todays strong catch-and-release ethic, but we cannot rule it out as a potentially adverse side effect. For turnover ratio to increase, some old males will have to be harvested. Because anglers cannot distinguish between the sexes, some younger females will be harvested too. But because females grow so much faster than males, their period of vulnerability as sub-slot fish will be about half that of males. In other words, females are almost twice as likely as males to successfully “run the gauntlet” of human harvest and reach a length of 40 inches, at which point they may safely grow to a trophy size of 50 inches, assuming angler compliance and sound release practices.In addition to selective harvest under slot limits, stronger measures may be needed to achieve trophy management goals for muskellunge fisheries. We may want to think about regulating the way live bait is used in order to minimize accidental mortality. We may also want to ask our tribal neighbors to focus their winter spearing efforts on lakes with abundant muskellunge where selective harvest of overabundant, small muskies may actually help restore balance in the fish community. This would be consistent with a cultural tradition of resource stewardship, and it would minimize health risks associated with consumption of mercury, which is more concentrated in older, larger fish. Combined, these approaches could be good for everyone if we are all willing to adopt a conservation ethic that includes selective harvest.So where are those waters where harvest should be encouraged under a 34- to 40-inch slot length limit? My staff and I plan to recommend replacing all 28-inch minimum length limits in the Upper Chippewa Basin with this low slot. In Ashland County, these waters include Day, East Twin, Potter, the Spider/Moquah chain, and Spillerberg lakes. In Iron County, Owl Lake has a 28-inch minimum length limit. And Sawyer County lakes with the reduced length limit include Black, Mud/Callahan lakes, and the Tiger Cat chain. There may be other waters with high density and slow growth, but these Upper Chippewa Basin waters have consistently produced more muskellunge than are able to grow at a satisfactory rate or achieve a desirable size. Angler harvest of small fish from these lakes would likely help the remaining muskies and the overall fish community. Anglers who struggle with the notion of keeping a musky under any circumstance might try thinking of muskies in such waters as if they were northern pike. On a good day, it is possible to catch several muskies in these lakes. Would that not be considered outstanding pike fishing? Would you not keep a pike to eat occasionally?Can we all work together to harvest more muskies in the instances where harvest may be helpful, and to harvest or incidentally kill fewer large muskies in waters where the production of trophies is both possible and desirable? Time will tell. But I am convinced that the proven principle of “selective harvest” introduced by visionary leaders in the sport fishing industry decades ago should continue to guide the management of all fishery resources.Dave Neuswanger, Fisheries Team LeaderUpper Chippewa Basin, Wisconsin DNRMay 30, 2007