This is an article from December/Jan In-Fisherman in regards to growing trophy pike and proper management. If proper management tactics are not enforced, we will start seeing smaller and more numerous pike in our waters. Whether you are for or against pike, they are here and here to stay. Proper management is critical to the state to turn this unwanted “junk fish” into a productive and economically beneficial trophy fishery.
Understanding big pike
Recruitment, growth, and mortality: three words that on the surface may not make an anglers ears ring but buzz loudly in a fishery biologists. These three rate functions are important because they interact with fish populations. Recruitment and growth add, mortality subtracts. What results are characteristics of a fish stock age structure size structure and density at any point in time. Sounds like a simple equation. Yet careers are made trying to understand the nuances of these connections what affects the rate functions how to best measure them and how to most effectively manipulate them to achieve some desired end result.
In the realm of pike management, a common goal is to increase pike size in systems where later pike once swam or where at least more common. Another is sustaining top notch populations that currently exist. Although we don’t have all the answers yet, and it takes biological time to see results, the science is advancing on how to get the job done. Meanwhile, as progress inches forward, pike fisheries may be experiencing new challenges.
Pike Places
Habitat has a strong, if not the greatest , influence on pike reproductive success, recruitment (survival to adulthood), and growth rates. Meeting basic environmental requirements is a start, such as pike being a cool water species with a specific thermal niche. Beyond that, what the characteristics of waters that historically produce big pike over the long run?
That’s a question Peter Jacoson, fishery researcher with the Minnesota DNR, approached using long term fishing contest data for pike caught in northwestern Minnesota lakes between 1924 and 1989. He asked: What factors are correlated with catches of trophy pike ( those greater than 15 pounds) on a per acre basis? More big pike came from larger deeper lakes with small littoral zones (areas less than15ft ) biomasses of pray fishes suckers, perch and ciscoes were also related factors.
Jacobson concluded that trophy pike management has the best chance of succeeding in lakes that maintain a cool (68 degree F) water throughout summer, and that larger deeper lakes with ciscoes may show the most promise. Small pike, thought, grew best in shallow fertile lakes with long growing seasons.
Along similar lines, Minnesota fishery biologists Rod Pierce and Cynthia tomcko examined how characteristics of Minnesota lakes affected pike density and biomass. While the density of pike exceeding 14 inches was lined to the percentage of littoral habitat, lake area and shoreline length were more important factors for pike longer than 20 inches, the largest length group tested in the analysis.
All this points to connections between big pike and deeper, larger waters with thermal refuges during summer, along with coldwater forage like ciscoes. Make water too warm eliminate thermal refuges, and pike become stressed, suffering longer periods of reduced growth in summer.
This is a phenomenon I observed while working on my dissertation research at South Dakota State University, Tracking seasonal growth of pike trough monthly samples at Lake Thomson, a shallow windswept glacial lake in eastern south Dakota, growth ceased in summer while water teps climbed through the mid to upper 70s. The lake didn’t stratify so no thermo cline related thermal refuge existed. Annual growth rates were astoundingly fast overall however occurring during the cool and cold water periods. But pike tended to top out in the upper 30in range.
Limited production of trophies at lake Thompson points to a live fast die young lifestyle in warmer waters such as those at the southern fringe of the pikes distribution. When I examined pike entries (15puonds or 34 in) in south Dakota anger awards program during the years around the timeframe of my research, only 6% were caught from the states natural lakes the majority taken from large deep reservoirs that thermally stratify.
Recruitment Factors
All this isn’t to say tat smaller lakes don’t produce big pike, In fact, decades ago, 10 iners extracted from select little gems around our Brainer Minnesota headquarters and elsewhere in the pike belt weren’t uncommon. The habitat was there and harvest hadn’t yet taken its toll. Today, its rare but still possible to hook up with a legit gator at some of these locales. But for trophy pike on small waters, the best bet s are private lakes or remote waters with little pressure.
Unless a lake has been substantially impacted by shoreline development or where adjacent wetlands used as spawning habitat have been destroyed, most pike lakes don’t have a lack of natural reproduction. Although habitat loss is a serious issue on some waters, a major limitation to managing for big pike in smaller lakes is that many of them are actually too good at producing pike – small ones.
Recruitment is a function of reproductive success and survival to adulthood. To successfully recruit young fish need to grow and service the gauntlet of predation exploitation and other sources of mortality. The higher the recruitment though the more numbers and usually pounds of pike in a lake. As pike biomass increases, competition rises, a factor that can slow growth, What can result is a stunted pike population a large number of slow growing pike with a high natural mortality rate. Here you might see upwards of 100 or more adult pike per acre, as opposed to less than five or so per acre in waters with low recruitment
Recruitment tends to be related to lake size with problems of high recruitment affecting mostly smaller water with emergent vegetation covering a large proportion of the surface area. Larger lakes are rarely afflicted with stunted pike. Overpopulation has also bee attributed to lake of appropriate slippery and over harvest of lager pike or a combination of these factors.
Managing exploitation
Anglers select for ad harvest larger pike. In Minnesota for instance pike longer than about 24 inches make up a large portion of he harvest. “we’ve seen harvest rates as igh as 465 for pike longer than 20 inches “ Pierce says. The result of this size selectivity is that numbers of bigger pike have suffered.
In a set of orth central Minnesota lakes he fouhd that 9 to 10 pike longer than 14 inches exist per acre onf water on average. Compared to only a half of a pike per acre for fish longer than 24 inches.” besides density, we can also look at production rates the amount of tissue produced on an annual basis to provide some indication of how much harvest a fishery can sustain,” he says. “Its really low for the largest pike in a population. The second and third growth years made up 60 to 87% of the annual production while pike age 6 and older averaged only 4 percent.
That equates to an average production of only a tenth of a pound per acre per year for pike ages 6 and older. Theoretically if you had a 100 acre lake and removed a 10 pound pike you’d use up the entire production of lager pike for a full year” he says.
From the persoetive of angling effort, Ontario biologist tTom Mosindy walter momot and peter bolby found that as little as 1.2hrs per hectare of fishing effort removed 50% of the annual pike production in a Canadian shield lake. More fertile waters can produce more pounds of pike per acre and with stand more harvest but these numbers show how vulnerable the largest pike in a system are.
Length limits may be the most effective regulation tool for managing harvet and growing larger pike and correct choice of length limit depends largely on recruitment. Where recurrent is high and there are high densities of slow growing pike protected slot length limits allow harvest of small pike. The intent: thin the numbers of smaller pike to improve growth and size structure of the remaining pike while protecting larger fish within the slot. The problem. : anglers generally don’t harvest small pike enough to show any effect Improvements if any tend to be due to some pike making it through the growth bottleneck into the protected slot.
High minimum length limits are a better choice for preserving or resorting a trophy pike on waters with low recruitment low density and god growth potential. High slots maximum length limits and catch and release are other options to restore big pike or to pressure unexploited trophy fisheries once there opened to fishing suck as the gator factories in the far north.
Since 2003 over 100 lakes in Minnesota have received special length limit regulations one of three in a toolbox of choices based on pike population characteristics a 24-36in protected sot, 30in minimum and 40inch minimums. Those lakes are under evaluation for10 years
Pierce however has completed an evaluation of experimental regulations that were imposed between 1989 and 1997 lasting 9 to 15 years.” Those include some slot limits (20-30 in or 22-30 inch maximum ) and a few 30 inch minimums. Although the length regulations did not work in very lake the bottom line overall was that statewide length limits had a relatively large effect on size structure compared to reference lakes. The strongest effects seemed to be from maximum and minimum length limits whereas the slot limits had more mixed results probably due to the most fragile of lengths that were protected. In all length limits seem to be one of the most promising tools we have found for managing pike populations one of the more interesting results is that we didn’t detect any consistent reductions in pike numbers with the length limits. We had fully expected that improving size structure would result in lower density and that has not happened yet.
