The announcement last week that night fishing would be banned this year on Mille Lacs and that the walleye limit there would be one — as in one — was not unexpected. Given the relatively few walleyes that swim in the lake these days, a declaration making Mille Lacs walleyes entirely catch-and-release beginning with the May 9 opener could have been justified.

That the state's premier walleye fishery could decline so far so fast suggests skulduggery on many fronts, and the inclination is to point fingers. Indian nets are to blame. Or the Department of Natural Resources. Or the U.S. Supreme Court, which ruled 5-4 in 1999 that eight Minnesota and Wisconsin Chippewa bands reserved off-reservation hunting and fishing rights in what is now a 12-county region of east-central Minnesota, including Mille Lacs.

Yet whatever short-term comfort might be realized from casting blame, and some blame is due, ultimately no good will come of it. The choice now is to keep complaining, or to support DNR and tribal fisheries researchers in their efforts to boost Mille Lacs walleye numbers, even if those numbers ultimately all short of historical highs.

Let's recap how we got to this point with Mille Lacs, where we are now, and where we're headed:

• State fisheries managers couldn't have known when they were first required to divide the state's Mille Lacs walleye spoils with tribal netters beginning in the 1990s that the task they were given was impossible to achieve. Or nearly so — assuming their charge also was to maintain the lake's walleyes at historically high levels.

Fisheries management is challenging enough in rivers, lakes and reservoirs, all of which are in constant flux, when only one user group and fishing methodology has to be satisfied. Add another user group, especially if its catch methods are diametrically different from the first, and management becomes exponentially complicated.

The walleyes that made Mille Lacs famous are in smaller numbers than ever, leading to strict regulations and plenty of anxiety.

• Within the context of the lake's challenging walleye co-management task, state fisheries managers now concede they made a key mistake. In dividing up the "safe allowable harvest'' — the number of walleyes they believed could be taken from the lake without harming its population — state and tribal biologists thought they could sustainably harvest 24 percent of the lake's walleyes longer than 14 inches.

Inadvertently, what occurred instead, says DNR fisheries chief Don Pereira, is that "we took 24 percent of a narrower size range of walleyes between 18 and 20 inches.''

This occurred, Pereira said, because Chippewa nets and sport-angling regulations targeted the same size fish, and also because the nets unexpectedly harvested a larger-than-expected number of young male walleyes.

• DNR researchers also now believe that even before Mille Lacs walleyes were co-managed by the state and the Chippewa, many juvenile walleyes in the lake for reasons unknown were not surviving to adulthood. This problem has only grown worse, and now fisheries managers are hoping the lake's 2013 year class of walleyes will survive in numbers sufficient to help rebuild the lake's population.

"We don't know why, but they're [the 2013 class] coming through OK at this time,'' Pereira said. "But we have two more [population] assessments to do before we declare they are going to come on pretty strong for us.''

The 2014 class, meanwhile, is doing OK. So far. But while walleyes in that class are abundant, the individuals are small, perhaps because of cool weather last spring and early summer.

In an attempt to figure out why entire classes of walleyes appear to be suffering in Mille Lacs, researchers are studying the diets of various predators, including smallmouth bass and northern pike, both of which are enjoying population heydays in the lake.

• Aquatic invasive species now in Mille Lacs possibly play a role in the lake's current game fish mix. Zebra mussels, spiny water fleas, Eurasian watermilfoil — these in combination with the clearer water that zebra mussels bring, which in turn spurs vegetative growth, and the lake's heightened numbers of northern pike and smallmouth bass might affect the lake's walleyes adversely for reasons unknown, and in ways unknown.

• Going forward, the greatest immediate challenge for fisheries researchers is to determine why so few Mille Lacs juvenile walleyes are surviving to adulthood. If that can be accomplished, the next test would be to devise a strategy to reverse the die-off trend.

A complication here, however: The same problem with dying juvenile walleyes might be occurring in other lakes, among them Fish Lake (actually a reservoir) not far from Duluth, as well as in various northwest Wisconsin lakes. If this phenomenon is in fact not limited to Mille Lacs, finding a solution might be more difficult than if the problem were Mille Lacs-specific.

• The good news is that fisheries experts know more about Mille Lacs walleyes now than they ever have. So if these fish can be stabilized, their harvest division between state and tribal factions likely will be done differently than in recent years.

Example: In an effort to expand the size distribution of harvested walleyes, sport-angling regulations might target one size fish one year, and another size the next. Similarly, mesh sizes of Chippewa nets would be altered to target a wider size distribution of walleyes. Additionally, Pereira said, the Chippewa would be encouraged to take a greater share of their harvest by spear, rather than by net. That way, sizes of harvested walleyes could be more widely distributed.

• Many challenges remain. One is that adult walleyes are among fish that eat juvenile walleyes, and if fisheries managers successfully increase the abundance of walleyes between 15 and 20 inches (typical sizes anglers prefer), they necessarily will intensify predator pressure in the lake. Again, this might or might not occur to the detriment of walleyes, depending on the number of ciscoes, perch and other baitfish in the lake.

• Finally, a little serendipity wouldn't hurt. Mille Lacs juvenile walleyes must survive in greater numbers. Fisheries researchers and managers could use a break to help them better understand the fishery. And continued cooperation between the state and the Chippewa is needed so Mille Lacs can better satisfy the interests of both.

Who can say? All of that might happen sooner than anyone thinks.

What is known is that spring is here and summer is nigh.

Time, as they say, to shut up and fish.

Dennis Anderson danderson@startribune.com