Age Data Important To Walleye Management In South Dakota
PIERRE, S.D. (AP) — South Dakota is a tough place to be a fish.
Most of the time a walleye living in the state won’t live past its sixth birthday.
That’s a fact proven time and again over a few decades, a number of research studies and several years of Game, Fish and Parks Department biologists counting the rings on fish ear bones known as otoliths. It informs their regulation recommendations to the Game, Fish and Parks Commission and acts as a signal for when the rules on a lake need to change.
Walleyes in the South Dakota’s Missouri River reservoirs are no exception when it comes to age structure, said Fisheries Program Administrator Geno Adams. Data from the Game, Fish and Parks Department show that six years is about as long as most Missouri River walleyes last, though there are a few that do live longer.
On Lake Oahe there are maybe one or two of the hundreds of otoliths biologists see from Lake Oahe in a year that will be about 12 years old, Adams said.
“That’s a drop in the bucket,” he told the Capital Journal ( ).
Fish tend to live longer when there is a more constant source of food and Lake Oahe generally has a lot of food available, Adams said.
Before 2009, the department had eight separate minimum length limits that applied to nearly 30 different bodies of water. There were length limits of 14 inches on some lakes and 16 inches on other lakes, for example. The problem was all the different length limits were actually accomplishing the same thing, it didn’t matter if the limit was 14 inches or 24 inches.
“One of the things we learned over time is these small little categories don’t do much,” Adams said. “Small, incremental differences in length limits were accomplishing the same thing.”
So in an effort to simplify regulations and better manage the state’s fisheries, the commission approved a plan in 2009 called the Walleye Toolbox. That created four minimum length limits and allowed for experimental regulations. None of the minimum length limits is under 15 inches and one allows for trophy fisheries with a limit of one fish over 28 inches.
The idea, Adams said, was to set rules that would have the best results for anglers and fish populations on the state’s lakes in six to eight out of 10 years.
But, Adams said, biologists know that there are no rules that will work best in every year — nature just isn’t that cooperative, especially in a region that is prone to wild weather extremes.
“Nothing lasts forever in South Dakota fisheries,” Adams said.
As a general rule, biologists want walleyes to grow to 15 inches long in about three or four years. That gives anglers a longer shot at the bigger fish. And on the lakes with minimum length limits, that gives anglers a better chance of catching keepers.
If the fish in a lake don’t meet that goal, biologists start taking a look at making changes to the regulations.
The folks who fish glacial lakes in the northeast corner of the state are finding out what that means first hand. Many of those lakes didn’t exist 30 years ago and those that did were a fraction of the size they are now. Thanks to a combination of a long wet cycle in the Prairie Pothole Region and, as new studies are beginning to show, increased tile drainage in the area, lakes and sloughs exploded in size.
As they grew, those lakes covered tons of vegetation, which translated to tremendous productivity. Fish grew fast and in impressive numbers and anglers took advantage.
Fast forward a few decades and that productivity has started to wane. That means fish are growing a bit slower these days. Opitz and Bitter Lakes are good examples.
In Bitter Lake, a huge number of fish were born in 2011. Four years on, and the vast majority of those fish still haven’t quite hit 15 inches, which means anglers can’t keep them. Bitter Lake has a 15-inch length limit.
The walleyes probably wouldn’t have been available to anglers before they started to die off naturally, according to the science. So the biologists asked the commission to pull the length limit from the lake. The idea being to allow anglers to take the smaller fish before they died of natural causes.
The commission recently approved the change. It will take effect Jan. 1.
On Opitz Lake the number of fish 15 inches and below far outstrips the number of fish over 15 inches, and they aren’t growing fast enough, either. On Opitz, anglers are restricted to keeping two fish over 15 inches per day.
Here, too, the biologists wanted to revert to the statewide limits. The proposal, however, was nixed last week as the other big driver of fisheries management, public opinion, reared its head.
Opitz Lake anglers spoke up both by writing letters and driving across the state to be in Spearfish for a recent Game, Fish and Parks Commission meeting to voice their fear that a more liberal limit would devastate the fishery. There were a total of 149 comments against changing the rules on Opitz Lake
“Our area is in trouble as far as walleye fishing,” Joe Honer, of Eden, said during the meeting. “This proposal has nothing to do with what’s in the lake now, it’s for in case they have another big year.”
The commission eventually decided not to change the rules on Opitz Lake.
