Lakecaster Online

Approaches to Manage Crappie Fisheries Varied and Controversial

 

Crappie fishing at our big East Texas lakes ranks right up there with bass and catfish angling in popularity based on creel survey statistics. It is therefore probably reasonable to conclude from the recently published economic impact study on Toledo Bend Reservoir that the $38 million dollar value of boat fishing to the economy is supported amply by crappie fishing. The management of viable populations and fisheries is clearly a priority. Management efforts by conservation agencies to provide stable year to year crappie fisheries have proven difficult at best since these populations tend to be cyclical, producing abundant year classes every 3-5 years. While a complete understanding of erratic year class strengths eludes researchers, several factors have been found to have an influence. These include turbidity, seasonal water level and fluctuations, water retention, reservoir morphology, bottom substrate at spawning site, and wind speed. Because these, for the most part, are environmentally related, little can be done to moderate or eliminate their effects. Of these factors, two having considerable impact- seasonal water level fluctuations and retention time- may be controlled to some extent by reservoir operations.

The most commonly used approach to stabilize crappie fisheries is the implementation of harvest restrictions. Daily bag limits alone are the least restrictive, however, anglers may harvest too many young fish when the supply of larger fish is low. Minimum length limits are attractive in situations where exploitation (harvest) is high and fisheries are erratic because they are designed to conserve fish stocks. A research study on 3 Texas reservoirs in the 1980's showed unregulated, exploited crappie populations were comprised primarily of small, young fish. The investigators termed this "growth overfishing"- the taking of available fish as they reach harvestable sizes. Positive effects (improved population structure, harvest) were reported following the implementation of 10-inch minimum length limits at these reservoirs. As a result of this study, a 10-inch, 25-fish bag limit was implemented for crappie on all waters within the state's jurisdiction in 1990. The excessive mortality of hooked (played) fish could potentially prevent any minimum length limit from having the desired effect. Studies addressing this issue typically have shown the loss of fish from hooking and handling to be inconsequential. In some cases, restrictions are eased during periods of excessive mortality; an example of this is the three-month winter period at Toledo Bend Reservoir. While minimum length limits have been used successfully in a number of situations, they are not recommended where crappie natural mortality is high and growth slow. Under this type of scenario, researchers have found protection of a length range of fish with minimum length limits provided less harvest and yield to anglers than what would be expected with a bag limit alone. In some of these studies, black crappie were the predominate species suggesting higher mortality rates for this species. For this reason reservoirs with predominately black crappie populations may not be good candidates for minimum length limits.

Crappie populations and fisheries at Toledo Bend and Sam Rayburn reservoirs were monitored using frame netting and creel surveys from 1986-1997. Data were analyzed to compare the effects of the 10-inch minimum, 25-fish bag limit on crappie imposed at Sam Rayburn in 1990 with that for the 50-fish bag, no minimum on crappie imposed at Toledo Bend in 1988. The primary results of this study will be presented in the next issue. The previously referenced Texas research study is available at www.jas.net/~tpwd3d

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