How to fix Mille Lacs: One man's perspective

Editor's note: In the commentary below, Dick Sternberg of Deephaven offers his insights on current Lake Mille Lacs walleye management. He is a former DNR fisheries biologist who 12 years ago forecast problems for the lake's walleyes. The Department of Natural Resources and Great Lakes Indian Fish & Wildlife Commission (GLIFWC) have been invited to offer their versions of the Mille Lacs situation to appear in coming weeks.

It's been more than a decade since I worked on behalf of the Mille Lacs landowners group to expose threats to the walleye fishery that had begun to develop as a result of the new court-ordered "treaty management" program. With fish-management decisions being made on the basis of treaty dictates rather than biological facts, most of the serious fisheries problems we are experiencing today were easy to predict. Now, after 15 years of treaty management, the walleye population is at a historic low and the Department of Natural Resources seems to be at a loss as to how to solve the problem.

Upon hearing of the walleye nose-dive in 2012 (4.8 walleyes/inshore gill-net lift down from 9.7 in 2011), many felt that the netting results were an anomaly — the population couldn't possibly have plunged by more than 50 percent in a year. So there was great interest in the 2013 netting results. At first glance, the net counts looked like a big improvement over 2012 — from 4.8 walleyes per net to 8.7 per net in the inshore, and from 9.9 per net to 19.2 per net in the offshore. But a closer look at the data revealed that 55 percent of the walleyes netted (365 out of 660) were large young-of-the-year. Normally, only a few of those walleyes (less than one per lift) are taken in the gill nets; most are too small to get caught in the mesh.

To get a more accurate picture of how the walleye population is really doing, I looked at the gill-net counts from both 2012 and 2013, not including young-of-the-year. That leaves the 2012 count at 3.8 in the inshore and 9.2 in the offshore nets. The 2013 count stayed the same (3.8) for inshore, but the offshore count dropped to 8.7. In short, the 2013 netting is no cause for optimism.

Hopefully, the larger young-of-the-year will survive better than many other recent year classes and contribute to a future recovery. But as the DNR warns in its recent letter to the Mille Lacs Input Group, "We have seen very good walleye reproduction the past few years only to have these young fish experience high natural mortality at young ages, likely due to predation."

You can find the DNR's assessment of the dismal walleye situation on its website (dnr.state.mn.us/millelacslake/index.html) under Background FAQ. They admit that "a serious problem has developed; not enough small walleyes are becoming big walleyes."

The DNR says: "The problem is complex. Many things are or have been going on at once. They include targeted harvest on smaller and younger walleye, more northern pike and smallmouth bass feeding on walleye or what walleye eat, more walleyes eating walleye, more unwanted aquatic invasive species, a smaller forage base, and less system predictability due to unknown interactions between fish community and new aquatic invasive species."

Another omission: the alarmingly low percentage of males in the walleye population. In the 2013 sampling, only 39 percent of the walleyes were males. DNR biologists suspect that the gender imbalance is the result of the tribal harvest, which runs 80 to 90 percent male, in addition to the nontribal harvest, which is heavy to males because slot limits force anglers to target the smaller fish. The long-term effects of the gender imbalance are unknown.

What is most concerning to me is that many of the most serious problems on the DNR's list have persisted for more than a decade. In my 2003 paper, "It's Time for a Change," I wrote at length about the population imbalance that was resulting from an ever-tightening slot limit that allowed harvest of only smaller walleyes. "As long as the Mille Lacs walleye population remains heavily skewed toward the larger size classes, the threat of heavy cannibalism of young-of-the-year walleyes will persist," I wrote.

But the DNR didn't need my input on the issues of cannibalism and heavy predation by other fish species; it knew exactly what was going on. "The pattern of year classes starting out strong but diminishing significantly over time has been occurring since 2000," DNR said in the 2008 Technical Committee report. "Lower survival of young fish may be a recruitment response to the increased numbers of large fish since treaty management began in 1997," it concluded.

So if the DNR understood this problem and most of the others on the above laundry list, why hasn't it taken stronger action to solve them? Cannibalism, for example, could be reduced by adjusting the slot to allow more harvest of large walleyes. That, in turn, would increase levels of perch and other forage fish, thereby benefiting smaller walleyes. But as the DNR reminds us every time this solution is proposed, harvest of more large walleyes would put us above the safe harvest level as dictated by the treaty management system.