There is a quote that says: “counting fish is just like counting trees — except that they are invisible and keep moving.” That is accurate, but we still try.

If you have ever purchase a couple of dozen minnows at a bait shop, then you will understand the difficulty of trying to count fish. Sometimes that “couple dozen” looks like 20, and sometimes it looks like 200. They don’t stand still, and often they all look alike.

However problematic to pull off with some degree of accuracy, fish surveys are a valuable tool in the management of the resource, and this is especially true on Lake Erie, where the resource is so precious to so many.

Lake Erie is a flattened gravy boat filled with “ests” — the warmest of the Great Lakes, the shallowest of the Great Lakes, and the undisputed fishiest of the Great Lakes. The walleye fishery in Lake Erie is widely regarded as the best-est in the world.

The home run statistic is this: Lake Erie holds only two percent of the water in the Great Lakes, but it is home to 50 percent of the fish in the Great Lakes. Flip that stat over and we learn that big, deep, cold, and crystal clear Lake Superior has 50 percent of the water in the Great Lakes system, but only two percent of the fish.

So we take inventory of that Lake Erie fish stock every year, surveying the walleye and yellow perch numbers while realizing that it is environmental and economic gold swimming around out there. Sportfishing is big business on the Ohio and Michigan sides of the lake, and commercial fishing dominates the waters on the Ontario side.

Ohio and Ontario do fish surveys by conducting trawls, which amounts to dragging a strong net along certain areas of the lake bottom, and then inventorying what the net brings up. Usually done in August, this method allows biologists to gain some picture of the success of the spring hatch, since by late summer those new fish are large enough to be caught in the nets. The relative success of the hatch gives biologists a way to anticipate future populations.

Trawls have been used in the western basin for more than 45 years, and in the central basin for 25 years. Western basin surveys are conducted at 41 sites between the Michigan border and Huron, Ohio, while the central basin surveys are done at 51 sites from Huron east to the Pennsylvania border. A 10-minute trawl is done at each site and the same sites are used each year to give biologists comparative data. The eastern basin is not included, because the western and central basins hold much of the primary walleye habitat.

The participating agencies also collect harvest information, and formulate some picture of the number of fish harvested from each age class. All of the trawl numbers are fed into a computer model, along with previous hatch figures, and a population estimate is formulated. From those estimates a harvest policy is then created.

Once that harvest framework is established, the total allowable catch (TAC) for walleyes and yellow perch are set, and those numbers are divided between the partner agencies that manage Lake Erie’s fishery.

“We don’t want to fish the population too hard, and we always want to make sure the population can rebound,” said Chris Vandergoot, a biologist with the Ohio Division of Wildlife’s fisheries unit in Sandusky. “In general, when we see a good hatch in August, that means we should see a stronger population in two years. Our walleye numbers are down a little in terms of historical perspective, but a good hatch last year should bode well for the future.”

The walleye class of 2003 is still the champion, and those fish make up a lot of the trophy walleyes caught today. The stronger classes from 2011, 2010, and 2007 are also primary contributors to the current fishery.

Lake Erie is divided into Ohio, Michigan and Ontario sections when walleye assessments are done, based on the amount of lake habitat located in those jurisdictions. The TAC is then divided among those parties based on their share of the lake: Ohio 51.11 percent, Ontario 43.06 percent, and Michigan 5.83 percent.

New York and Pennsylvania are not part of the walleye quota computations, but their numbers are included in the annual harvest figures. Since yellow perch habitat is more widespread throughout the lake, those two states to the east are included in the yellow perch TAC figures.

Vandergoot emphasized that the TAC numbers are not harvest targets, but instead indicate what is projected to be the ceiling on that year’s harvest, without doing harm to the long-term health of the fishery.

The TAC is rarely reached. The last time it was exceeded was in 2004 when the TAC for walleyes in the lake was set at 2.4 million and 2,451,794 fish were harvested. Last year’s TAC was 4,027,000 walleyes and 2,868,977 were harvested.

The TAC recommendations for 2015 represent a three percent increase in allowable catch for walleye and a five percent decrease in yellow perch.

Vandergoot said the sharing formula between the states and Ontario has been in place for about 30 years. Ohio still has a few commercial fishing operations for yellow perch, but does not permit commercial fishing for walleyes. Ontario allows commercial fishing for both species. The majority of Ontario’s allocation goes to commercial fishermen.

“International management gets a bad rap a lot of places, but here it is something that really works,” Vandergoot said. “This is the only way to do it — as a cooperative venture between states and nations. We have a great partner in Canada.”

Vandergoot said Ohio’s bag limits for walleyes and yellow perch have not changed, and that the TAC figures will have very little impact on the individual angler.

“We are trying to understand the dynamics of our fishery, and tailor the harvest policy to account for changes, but the fishermen out there won’t really see this,” he said. “The bottom line is — there are a lot of fish in Lake Erie, and you are going to be able to go out there and catch fish.”

Contact Blade outdoors editor Matt Markey at: mmarkey@theblade.com or 419-724-6068.

First Published April 5, 2015, 4:00 a.m.