“Why don’t we hear about more studies of pike and muskies?” an angler asks. “After all, they’re among the most imposing predators and rank high in angler preference wherever they’re found.” It’s true that fishery science journals have increased in number and page count, so maybe the relative lack of research on pike and muskies is indeed surprising.

The world of fishery science is moving fast, thanks to new technology and methods of genetic analysis, as well as new emphasis on studying whole ecosystems rather than single species. More studies now focus on threatened or endangered species and the habitats they rely on. The effects of new invasive aquatic species is another hot topic. But these areas of investigation don’t much apply to pike or muskies, save for the effects of newfound diseases such as Viral Hemorrhagic Septicemia.

Much recent research on esocids has evaluated muskie stocking procedures, since many fisheries rely on them and fish are costly to produce. With limited budgets, high priority goes towards maximizing efficiency of operations so fish can survive and grow after stocking. Pike, on the other hand, rarely require replenishment, more often overpopulating lakes where anglers have removed too many big ones.

Another current avenue for research is measuring the efficiency of sampling techniques, to fine-tune the tools used to describe the size structure of populations. While this information is valuable to fishery managers, it’s not of high interest to anglers.

Length limits certainly affect fishing, particularly as they contribute to production of trophy fish. While some evaluations of muskie length limits have been done, particularly in Wisconsin, pike limits have been enacted mainly in the last decade, and only some preliminary evaluations have been conducted so far. Depending on level of reproduction, growth rate, and angler harvest in a body of water, three regulation types have shown promise: high minimum-length limits, protected slot limits, and medium-size, maximum-length limits. Biologists in Minnesota are currently studying their effectiveness in diverse fisheries.

Food habits studies are always fascinating, since the hunt for prey gives us the opportunity to catch fish in the first place. Tracking studies provide detailed descriptions of where fish go when, and in some cases, why they choose to move or remain sedentary, key information in formulating an angling plan.

Movement of Pike and Muskie

Even grizzled veterans admit that fish movements can be puzzling. We’ve sat with pro anglers, guides, and biologists, pondering the whys and wherefores of fish behavior or puzzling over lack of fishing success. The big toothy fish can be particularly frustrating, because they seem to move en masse for reasons that can be hard to decipher.

Biologists have tracked pike since the 1970s, revealing several key elements of preferred location and activity periods. In northern natural lakes and impoundments, vegetation keys pike location during summer, with preferred depth generally ranging from 6 to 15 feet. During ice cover, pike also prefer weedy water, though they may make forays into deeper open water, at times.

Where water temperatures may exceed the range preferred by larger pike, fish seek cool water, often by shifting deeper to hold along creek channels, flooded timber, or deep points. Pike generally tend not to establish longterm home ranges, however. Instead, they stay in restricted areas for periods ranging from a few days to several months, making short forays within this area of activity and sometimes outside it. After a time, however, they suddenly leave and establish a new activity area, often a considerable distance away.

Though not documented, this shift is likely due to food availability. While prey is plentiful, pike remain. But when a group of large predators has either cropped baitfish numbers or caused schools to leave the area, pike abandon this feeding ground and move elsewhere for more fruitful hunting.

Spawn-time Movements

Recent research has focused on spawning locations of pike, because shoreline development and loss of wetland habitat threaten areas essential for reproduction. Tagging studies have indicated that some pike return to spawning areas in consecutive years, emphasizing the need for protection of marsh habitat.

Though they’re used by adult pike only in spring and may become dry in summer, wetlands swell with late winter snowmelt and spring rains, drawing adults. Big pike thrash and chase about in water just a foot deep, finally depositing fertilized eggs on the stalks of emergent grasses or submerged terrestrial vegetation.

Biologists define two types of fidelity to spawning locations: Spawning site fidelity, when individuals return to the same spawning grounds in subsequent seasons, regardless of where they were born; and natal site fidelity, when fish return to spawn in the location of their birth. Natal site fidelity tends to result in reproductive isolation between spawning populations that may mingle at other times of year.

Recent advances in genetics have helped us to understand the homing of pike to spawning sites. Ability to analyze minute variations in DNA among fish has allowed researchers to determine how closely different populations are related. At Minnesota’s Lake Kabetogama, Dr. Loren Miller and colleagues tagged pike and genetically examined groups that spawned at two of the three key locations in this 26,000-acre lake.1

They found that adults tended to return to the same spawning location in subsequent years, though a few fish did spawn at the alternate location, which was a little more than 9 miles away. The percentage of straying from the Tom Cod Creek site to Daley Brook was 1 percent, while those straying to Tom Cod Creek from Daley Brook was 5 percent.

DNA analysis showed that this level of spawning segregation yielded populations with significant genetic differences. They concluded that pike showed both spawning site and natal site fidelity. This result adds to the growing body of evidence that populations of many landlocked freshwater species, including smallmouth bass, walleye, and yellow perch, may exhibit both spawning and natal site fidelity.

A follow-up study done on the Thousand Islands area of the St. Lawrence River found, however, that pike populations spawning in nearby marshes tend to be genetically closer than those spawning in more widespread locations, and that fish stray more when alternative spawning sites are close.2

Tagging studies have shown that muskies also tend to return to previous spawning locations in some waters, though genetic studies have not yet confirmed homing to natal sites. Muskies caught from an area and moved to another also have been able to return to their former area. The most dramatic instance was documented by biologist Terry Margenau, who followed a radio-tagged fish after it was caught on a lure in Tomahawk Lake in Wisconsin and displaced to Mid Lake, about 5 miles away through a winding channel.3 After recuperating in a weedbed for about three days, she departed and, after wandering a bit, returned near her point of capture just three days later.

Muskie Hooking Mortality

Developing trophy fisheries often requires strict harvest regulations such as high minimum-length limits or slot-length limits. Trophy muskie fisheries often are managed with high minimum-length limits. Moreover, a large proportion of muskie anglers practices catch-and-release of larger legal-sized fish to help sustain numbers of big fish. Hooking mortality can potentially hinder development of trophy fisheries, however.

A survey in Wisconsin, conducted by Terry Margenau and Jordan Petchenik of the Wisconsin Department of Natural Resources, showed that 62 percent of muskie anglers use artificial lures exclusively, 37 percent fish with either lures or livebait, and 1 percent use only livebait.4 Of particular concern among anglers surveyed was the effect of single hooks with livebait on muskie survival; 88 percent felt it causes mortality, and 79 percent believed that it should be regulated in some way. The baitfish, commonly a white sucker, is hooked through the snout. After a muskie strikes, it’s allowed to run and swallow the bait before the hook is set.

To address this concern, Margenau examined the effects of fishing with single hooks with livebaits on muskie survival.5 Forty muskies averaging 36 inches were captured by electrofishing and transported to a DNR hatchery pond for the angling experiment. Angling occurred in September and October and fish were observed for a year.

White sucker, northern hogsucker, and redhorse between 10.5 and 12.5 inches were used as bait. Baits were hooked through the snout on 10/0 Mustad carbon steel hooks attached to a 60-pound wire leader and 30-pound monofilament mainline. Baits were set below a bobber; after the strike, muskies were allowed to run and swallow the bait before the hook was set. The average time between take and hook-set was 17 minutes.

Hooked fish were landed quickly (less than 1 minute) to avoid stress and fatigue, and netted. Researchers noted hooking location, and if a muskie had swallowed the hook, the leader was cut before releasing the fish. Throughout the angling period, researchers swam transects at regular intervals to remove dead muskies and examine them. Survival was monitored for up to one year.

Twenty-three muskies were hooked in the stomach; 14 either were never hooked or were hooked superficially; and 3 fish were excluded from the experiment. Muskies hooked in the stomach suffered no mortality within 24 hours of release. Five died within 50 days, however, and 83 percent of stomach-hooked fish died within a year.

Examination of dead muskies showed considerable damage to the stomachs from hooks, with the largest tear being 41⁄2 inches long. In addition to rips and tears in stomach tissue, the barb was imbedded in the liver of one fish, and a barb had punctured the gas bladder of another. Infections and inflammation also were observed.

Hooks dissolved slowly in muskie stomachs. After about a month, hooks had corroded 9 percent, on average. Corrosion reached 29 percent by the following spring, and hooks were almost completely dissolved by fall (after 1 year). Hooks weren’t present in 3 fish and either had completely dissolved or had passed from the body.

The researchers conclude that such low rates of survival were unacceptable for a species managed for trophy potential. They suggest that while regulating single-hook livebait presentations is possible, enforcement would be difficult. Instead, they feel that increasing angler awareness of this problem would likely cause anglers to alter terminal rigging, such as using quick-strike rigs that allow immediate hook-sets and generally produce non-lethal hooking locations.

Results of this study may also have consequences for managing trophy pike, which are often targeted with a single hook and livebait during winter and spring. Margenau notes that stomach-hooked fish appeared healthy, with no bleeding, and swam off when released. A conservation-minded angler might believe that such fish can survive, yet Margenau’s results show there’s a good chance the fish will die within days or weeks.

Peculiar Pike Diets

Pike are known to be highly piscivorous, feeding on fish that can be surprisingly large. There are times, though, when pike are just as inclined to wolf a bellyful of tiny prey. The latter seems to be keyed to the abundance and availability of these smaller food types.

An earlier study by University of Alberta researchers Lauren Chapman, William Mackay, and Craig Wilkinson revealed some curious results about the food habits of pike in eight lakes in Alberta and the Northwest Territories.6 Overall, pike were primarily fish eaters, but consumption of invertebrates was high during spring. In three lakes, invertebrates (mostly amphipods, but also some mayfly and dragonfly larvae) made up 94 percent of the total number of items eaten. In lakes where invertebrate feeding was high in spring, it declined in summer as fish became a bigger component of the diet.

In-Fisherman staff traveling to Canada have become aware that pike, even big ones, sometimes seem to crave leeches. Particularly in spring, leech-imitators often outfish traditional presentations in far north lakes. Dark skirted jigs tipped with a soft-plastic worm, leech, or other softbait have became a top option. Today, the leech connection is catching on, with fly fishermen using black bunny-strip leeches and other smaller-than-usual offerings.

The pike-leech link was recently reinforced by the work of Paul Venturelli and William Tonn at the University of Alberta.7 They examined pike diets in small lakes of boreal Alberta, where winterkill can reduce or eliminate preyfish. Two reference lakes were dominated by pike and yellow perch. A third lake had been fishless for the previous six years. Pike collected from nearby Piche Lake, which contains a mix of preyfish species, were stocked in the fishless lake.

After being placed in the fishless lake, adult pike focused on energy-rich leeches, while juveniles ate a broader mix of invertebrates. In the two reference lakes, amphipods were the dominant prey, with fish, leeches, and larval caddisflies of secondary importance. The researchers conclude that pike can adapt quickly to a lack of preyfish. Pike growth was slower than at lakes containing preyfish, however.

As certain as fishery science moves forward at the quick-step, so too will research on pike and muskies. Among the most popular gamefish in freshwater and as key components in complex aquatic ecosystems, they deserve to go along for the ride.

Footnotes:

1 Miller, L. M., L. Vallemeyn, and W. Senanen. 2001. Spawning-site and natal-site fidelity by northern pike in a large lake: mark-recapture and genetic evidence. Trans. Am. Fish. Soc. 130:307-316.

2 Bosworth, A., and J. M. Farrell. 2006. Genetic divergence among northern pike from spawning locations in the upper St. Lawrence River. N. Am. J. Fish. Mgmt. 26:676-684.

3 Margenau, T. L. 1994. Evidence of homing of a displaced muskellunge. (Esox masquinongy). J. Freshwater Ecol. 9:253-256.

4 Margenau, T. L. and J. B. Petchenik. 2004. Social aspects of muskellunge management in Wisconsin. N. Am. J. Fish. Mgmt. 24:82-93.

5 Margenau, T. L. 2007. Effects of angling with a single-hook and live bait on muskellunge survival. Envir. Biol. Fish. 79:155-162.

6 Chapman, L. J., W. C. Mackay, and C. W. Wilkinson. 1989. Feeding flexibility in northern pike (Esox lucius): fish versus invertebrate prey. Can. J. Aquat. Sci. 46:666-669.

7 Venturelli, P. A., and W. M. Tonn. 2006. Diet and growth of northern pike in the absence of prey fish: initial consequences for persisting in disturbance-prone lakes. Trans Am. Fish. Soc. 135:1512-1522.