Bass management

The keys to maintaining good numbers of desirable-sized largemouth bass are protecting habitat and regulating sport fishing.

Largemouth Bass Management

Habitat Protection

Largemouth are adaptable and prolific. They live and successfully spawn in a variety of conditions. Being very prolific, only a few bass are required to populate a large body of water. Consequently, stocking plays a very small role in largemouth management. It is usually limited to circumstances where largemouth are being introduced to newly filled basins, winter kill lakes or chemically "rehabilitated" waters.

What is important in managing the largemouth is the protection of its habitat. Specifically, the largemouth needs the following if it is to flourish:

  • Spawning areas with a firm bottom of sand, mud or gravel.
  • Beds of rooted aquatic weeds or other heavy cover, such as logs, to provide protection for fry and fingerlings, and cover and ambush sites for adults.
  • Adequate dissolved oxygen, particularly during the winter.

State law protects these kinds of habitat in a number of ways.

Ecological types of Minnesota waters.
Average number of hours needed to catch a bass in each of Minnesota's ecological waters types.

Shoreland zoning and related laws aid bass and other fish by controlling lake and river shoreline development that otherwise might pollute lakes with septic-system drainage. This effluent contributes to eutrophication, which decreases water clarity and dissolved oxygen. The DNR requires that landowners first obtain a permit before working in the beds of public waters or removing aquatic weeds that provide cover.

Various state laws limit various kinds of industrial and sewage-plant pollution that deprive fish of oxygen or poison them outright. Other forms of pollution-such as soil erosion, pesticide runoff from farmland, manure runoff from feedlots, and storm runoff from city streets and lawns --also consume oxygen and contribute to algae blooms. These "non-point sources" of pollution are extremely tough to correct.

Winter aeration systems are a boon to shallow, marginal fish lakes in southern Minnesota. In the past, these lake would lose their bass to periodic winterkill. With aeration, however, these lakes produce fast-growing bass that survive from year to year.

Regulating Fishing

Bass fishing regulations haven't changed much over the past several decades. They still have two main features: a six-fish limit, and a season opener in late May, generally when spawning is complete. (An exception is found in northeastern Minnesota, where the bass season begins with the general fishing opener.)

These regulations don't protect large bass. Heavy fishing pressure--particularly by knowledgeable, well-equipped anglers --can drive down the average size of bass and affects other fish populations. Fish managers are experimenting with various size regulations for largemouth bass to protect fish of a particular size.

Fish managers have found that a "slot" limit protecting all bass between 12 and 15 inches increased the average size of the bass caught and caused bass to grow faster. Among the disadvantages of a slot limit are the catch rate drops as bass become not only large but also fewer. If the average size of the bass increases, the average size of the bluegill may decline. Why? Probably because a few large bass do not eat as many bluegill as a lot of smaller bass. So bluegill proliferate and begin to show signs of "stunting." Yellow perch, too, may figure into this complicated equation.

Another common size restriction is a minimum-size limit--12 inches is common in many states. All bass under a foot must be returned to the water. This restriction may have begun with the common but mistaken belief that releasing small fish will produce many big fish. Actually, only releasing big fish will ensure the presence of big fish. The minimum-size limit has the opposite effect: with heavy fishing pressure, the bass population "stacks up" under the limit. This horde of small bass may not be large enough to prey on small bluegill. In some metro-area lakes, a minimum-size limit for bass of 16 inches is being tried to create a population of small and medium-sized bass in the hopes that these predators will limit the number of small sunfish and increase the number of big sunfish. The effect of this size limit on bass is of secondary concern.

Fish managers recently have begun discussing the use of special regulations to create a trophy bass fishery. Under such a plan, a high slot limit might be used to protect truly large fish. For example, 16- to 22-inch fish might be protected. Thus, anglers could keep small fish (and reduce competition) as well as an occasional trophy (a 22-inch largemouth weighs about 6 pounds.) Another approach to producing trophy bass may be a simple no-kill requirement.

The exact effects of any size restriction or other change in regulations depend on lake fertility, fishing pressure, competition form other species, condition of the forage base and other factors that must be studied lake by lake.

Smallmouth Bass Management

Habitat

As with the largemouth, the best smallmouth management is the protection of its habitat.

Minnesota's smallmouth bass live in a variety of lakes and streams. Some waters have fared well; some have been completely destroyed as smallmouth habitat.

The lakes of northern Minnesota, including those of the Boundary Waters Canoe Area Wilderness (a nationally known smallmouth fishery), are in good health, suffering relatively little pollution. Still, acid precipitation threatens many of the lakes of the Canadian Shield. These granitic basins have little capacity to buffer the effects of acid rain. Even mildly acidic waters prevent smallmouth bass from successfully reproducing. (They are, in fact, one of the first species to be affected by acidification.) The smattering of smallmouth lakes across central Minnesota are better protected from acid rain by the greater buffering capacity of their more alkaline waters.

Smallmouth rivers have more immediate problems. The rivers of central and southern Minnesota suffer to varying degrees from poor municipal sewage treatment, farmland runoff, sedimentation from soil erosion and extremes in water level fluctuation.

Grazing livestock along bass streams causes banks to slough, increasing siltation and changing the profile of the stream channel from narrow and deep to broad and shallow. The consequences are warmer water, less dissolved oxygen, and fewer spots with the depth necessary to hold bass. Runoff from feed lots reduces dissolved oxygen and increases ammonia, killing bass and other fish.

Common pesticides, especially root-worm insecticides called organophosphate, wash off fields into streams and are particularly toxic to bass and others of the sunfish family. Biologists throughout the upper Midwest report that smallmouth bass have disappeared from many streams as corn production and insecticide use have increased. Several of the once productive smallmouth streams in the heavily farmed Minnesota River Valley are now devoid of bass or produce only a fraction of what they once did.

Perhaps the most pervasive destroyers of smallmouth streams are the quick, intense floods and siltation caused by the drainage of wetlands (which retard runoff) and the destruction of soil cover. Heavy spring rains raise a tide of chocolate-colored waters in small streams, often at the very time smallmouths are spawning. The productive limestone streams in the steep, erodible valleys of southeastern Minnesota are particularly prone to siltation, which destroys spawning areas for bass and forage species alike.

Given these environmental problems, the most important aspects of smallmouth management are the prevention of soil erosion, better containment of pesticides and feedlot runoff, the regulation of shoreline development, the reduction of acid rain, and better treatment of municipal sewage. Several agencies, including the DNR, are working toward these goals.

Regulating Fishing

Bass fishing regulations haven't changed much over the past several decades. They still have two main features: a six-fish limit, and a season opener in late May, generally when spawning is complete. (An exception is found in northeastern Minnesota, where the bass season begins with the general fishing opener.)

These regulations don't protect large bass. Heavy fishing pressure--particularly by knowledgeable, well-equipped anglers --can drive down the average size of bass affects other fish populations, fish manages are experimenting with various size regulations for largemouth bass to protect fish of a particular size.

Fish managers have found that a "slot" limit protecting all bass between 12 and 15 inches increased the average size of the bass caught and caused bass to grow faster. Among the disadvantages of a slot limit are the catch rate drops as bass become not only large but also fewer. If the average size of the bass increases, the average size of the bluegill may decline. Why? Probably because a few large bass do not eat as many bluegill as a lot of smaller bass. So bluegill proliferate and begin to show signs of "stunting." Yellow perch, too, may figure into this complicated equation.

Another common size restriction is a minimum-size limit--12 inches is common in many states. All bass under a foot must be returned to the water. This restriction may have begun with the common but mistaken belief that releasing small fish will produce many big fish. Actually, only releasing big fish will ensure the presence of big fish. The minimum-size limit has the opposite effect: with heavy fishing pressure, the bass population "stacks up" under the limit. This horde of small bass may not be large enough to prey on small bluegill. In some metro-area lakes, a minimum-size limit for bass of 16 inches is being tried to create a population of small and medium-sized bass in the hopes that these predators will limit the number of small sunfish and increase the number of big sunfish. The effect of this size limit on bass is of secondary concern.

Fish managers recently have begun discussing the use of special regulations to create a trophy bass fishery. Under such a plan, a high slot limit might be used to protect truly large fish. For example, 16- to 22-inch fish might be protected. Thus, anglers could keep small fish (and reduce competition) as well as an occasional trophy (a 22-inch largemouth weighs about 6 pounds.) Another approach to producing trophy bass may be a simple no-kill requirement.

The exact effects of any size restriction or other change in regulations depend on lake fertility, fishing pressure, competition form other species, condition of the forage base and other factors that must be studied lake by lake.

Smallmouth Stocking

As with largemouth, smallmouth are never stocked to add to an already vigorous population. Stocking is used only to introduce or reintroduce smallmouth to a body of water. A recent example in a riverain situation illustrates the difficulties in stocking.

A section of the Cannon River had lost its population of smallmouth bass. Fingerlings from a lake dwelling smallmouth bass population were stocked in this river section but were never found again. The following year fingerlings from a nearby river were stocked into this same river section. Today, anglers are catching many nice smallmouth bass in this river section.

Fishing Pressure

As far as regulations are concerned, smallmouth have been included with largemouth. Statewide regulations protect smallmouth during the spawning season and limit the overall harvest but do little to protect large bass in heavily fished waters.

Smallmouth can be easily "overfished" for several reasons:

  • Even in good smallmouth waters, smallmouth are not terribly abundant. They are never as numerous as trout are in a good trout stream, for example.
  • Many smallmouth waters, such as modest-sized streams, are shallow and easily fished.
  • In the fall, bass migrate considerable distances, sometimes dozens of miles downstream, and congregate in a few deep holes, where big bass can be easily caught.

An infertile area such as the Boundary Waters Canoe Area Wilderness retains its good fishing for trophy smallmouth bass because of its vast acreage and few people and because most anglers seek walleye, lake trout and northern pike rather than smallmouth. But where many anglers fish for bass, catch-and-keep smallmouth fishing can quickly drive down the average size and make big bass scarce indeed.

As a result, several states have used 12-inch minimum size limits to allow the fish to grow a bit before they are fried up and eaten. Nonetheless, 12-inch minimums are good at producing 12-inch fish, not 18-inch fish. And 12-inch fish are hardly trophies.

In a novel attempt to produce large smallmouth bass on a heavily fished section of the Zumbro River, the DNR established a 9-inch maximum size limit: all smallmouth larger than 9 inches had to be returned to the water immediately. Furthermore, fishing was limited to artificial to reduce hooking mortality. Early results indicate that the special regulations increased the average size of the bass in that section of the Zumbro while letting people take some fish home. Additional experimentation and, above all, better compliance by anglers will be needed to prove the worth of a maximum size limit.