Position

A length limit regulation can be an appropriate management strategy if certain conditions exist: (1) anglers desire larger fish and/or greater catch rates, (2) over harvest is occurring, (3) anglers are willing to comply with the regulation, (4) recruitment is steady, and (5) growth rates are good. If these conditions are present, a length limit can be selected which will have the best potential for improving the fishery.

Purpose

This position statement on the application of sport length limits in managing Ohio's fisheries will unify the Division's thoughts and approach to this management practice and improve the public's understanding of length limit applications.

Background

The Division's Fish Management and Research Group continually evaluates the potential application of old and new management strategies for improving our fisheries. Management approaches may change as the fisheries themselves change or as advances are made in the science and art of fisheries management. Fishery management practices can include stocking, habitat improvement, angler access development, or manipulation of the existing fish population. Manipulation of the fish population is often accomplished by regulation of the anglers or their harvests.

In the late 1940s and early 1950s, many restrictive sport fish harvest regulations were eliminated because they were not necessary given the low fishing pressure and angler desires at that time. As fish communities and conditions have changed, management techniques that were inappropriate in the past may now, under certain circumstances, offer potential for improving fisheries. In recent years, fishing pressure on Ohio's waters has greatly increased and the Division has greatly improved its capability to survey and measure fish populations. Length limits have been reevaluated and have provided positive results when properly applied.

General Principles of Regulations

Fish are a renewable resource which in many cases produce an annual surplus, over and above those numbers needed to maintain the population. Anglers can harvest this surplus without harm to the population. In some instances, regulations are required to limit the anglers' harvest to the surplus. Length limits are used primarily to increase fishdensities, which can improve catch rates, or to increase the size of fish in a population, which can result in larger fish for the fishermen. In some instances, length limits on predatory species (e.g., largemouth bass) can also be used to improve size structure of a prey species (e.g., bluegill).

Properly applied length limits can improve the quality of a fishery. Improperly applied length limits can slow growth rates and result in the loss of most fish to natural mortality before they reach harvestable size. Broad application of length limits, without consideration of all relevant factors, provides very limited or no beneficial results. To be most effective, regulations should be tailored to specific problems. The following guidelines will help ensure that all factors have been considered prior to the proposal of a length limit regulation.

Factors to Consider

The Customers: Anglers

Anglers differ widely in their attitudes about fishing. Some want to catch a few large fish, while others are satisfied to catch a large number of smaller fish. Some like to fish competitively, while others fish simply for relaxation.

Therefore, the first step when considering a length limit regulation is to determine the desires of the various angling groups: Do they want to release or keep the fish they catch? Do they want a lot of fish of any size, or a few big fish?

Angler attitude surveys provide the mechanism for determining angler desires. Knowing whether or not anglers will accept and comply with, the regulation is also critical to its success. Once the anglers' desires are understood, the fisheries manager can investigate various regulations that address those preferences.

Biological Factors

The aquatic habitat determines the potential numbers and sizes of fishes in a water area, while the anglers determine the harvest from and impact on the fish populations. By regulating the anglers' impact on a fish population, the population can sometimes be manipulated to produce the most benefit to the anglers. Limits on the size of fish the angler can harvest can be beneficial to the species being regulated if all the following conditions exist: (1) excessive harvest of all or part of the population, (2) consistent recruitment, and (3) good growth rates of all or part of the population.

The most obvious condition which suggests that a size limit will be effective is excessive harvest of the species to be protected. For most species, harvest is excessive if more than 30 to 40 percent of the population is removed by anglers annually. If excessive harvest is not occurring, a length limit generally will not result in measurable benefits to the population. Over harvest is measured by direct calculation of the harvest rate based on creel surveys and population estimates, by tagging studies, or by examining the age structure of the population. A scarcity of older fish indicates excessive mortality, due either to angler harvest or to natural causes. If natural mortality (e.g., predation or disease) is high, then restrictive harvest regulations will not be effective,

The second condition needed for an effective size limit is consistent recruitment; i.e., a steady supply of young fish entering the population. If recruitment is poor or variable, benefits from a size limit will be very limited. With only a few fish to protect, a length limit will not result in a noticeable improvement in fishing. Some anglers argue that protection of the spawners through length limits would improve recruitment. However, for most warm water species, no relationship has been proved between abundance of the spawning stock and recruitment to the population. Natural factors, such as weather and the amount and condition of spawning habitat, are the primary ones governing recruitment.

The third condition needed for an effective size limit is good growth rates. If growth is slow, few fish survive to legal size. In some areas, minimum length limits have resulted in a buildup of slow growing fish in poor condition, with even fewer fish reaching harvestable size than without a limit. In some cases, slow growth rates of small fish can be improved by using a slot length limit. A slot length limit encourages the harvest of small fish to leave more food for those that remain, while protecting the larger fish which exhibit good growth.

Conclusions

Length limits can be an effective management strategy to improve fishing for a specific fish species if the conditions specified in the position statement are met. If these conditions are not present, length limits can be counterproductive, reducing fishing opportunities and success instead of making improvements. For these reasons, the Division of Wildlife will impose length limits only where they have a good chance of success or for research purposes. Further, the effectiveness of existing length limit regulations will be monitored, and where appropriate, modified or discontinued to maximize benefits to the anglers.

12CM 15

4/13/88

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