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tennessee technological university


Physiology, Survival, and Dispersal of Tournament-Caught Largemouth Bass


The number of live-release fishing tournaments in North America has increased considerably since the 1970s, especially those targeting largemouth bass. Delayed mortality occurs after fish are weighed and released and can represent a considerable portion of total mortality associated with tournaments. Delayed mortality of largemouth bass through the 1990s in live-release tournaments was estimated to range from 10% to 23%.

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Tournament Fishing

nitial mortality and delayed mortality rates are strongly influenced by water temperature. Mortality is particularly high at water temperatures above 25 ° C (77 ° F). Researchers documented depleted muscle energy stores and elevated lactate concentrations in largemouth bass when they monitored Canadian live-release tournaments. The weigh-in process in live-release fishing tournaments has been shown to cause a physiological disturbance due to lack of oxygen in transfer bags and air exposure during the weighing procedure.

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Weighing In
In conjunction with researchers at Queens University (Ontario , Canada ) and the Natural Sciences and Engineering Research Council of Canada, the fishing tackle manufacturer Shimano, Canada, Ltd., developed the “Water Weigh-In System” (Shimano Water Weigh-in System) to reduce physiological effects on tournament-caught fish. This system is comprised of a series of troughs with aerated water. Each tournament angler receives a plastic tub with drain holes to hold his or her catch. The tubs and fish are submersed in the aerated troughs and fish are then weighed in a water basin on a scale that has been tared to discount the weight of the plastic tub, the basin on the scale, and the water. This new weigh-in method has been shown to reduce stress in tournament-caught fish because handling time and air exposure is minimized.
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Trough Weigh-in

The goal of our study is to evaluate the efficacy of a water weigh-in system in reducing stress and lowering delayed mortality compared to standard weigh-in procedures in Tennessee reservoirs. The specific objectives are to (1) compare the blood chemistry of largemouth bass caught in tournaments and subjected to either a water weigh-in system or a traditional weigh-in; (2) determine whether there is a relationship between the blood chemistry of tournament-caught fish and delayed mortality, and (3) describe dispersal and movements of largemouth bass after they are released from tournament weigh-in sites. We are conducting our research on J. Percy Priest Reservoir located in Davidson, Rutherford, and Wilson Counties, Tennessee .


We constructed three portable aluminum troughs (9' x 2' x 15”), which are transported to local bass club tournament weigh-ins at J. Percy Priest Reservoir. Each trough can accommodate five plastic tubs. Each tub has multiple drain holes, which allows water to drain quickly when the tournament angler reaches the weigh-in scale. Our water weigh-in troughs are also equipped with air-stones supplying bottled oxygen.

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Chad Holbrook at weigh-in station

We plan to monitor at least sixteen fishing tournaments (8 standard weigh-ins and 8 water weigh-ins) between March 2006 and June 2007. Fish subjected to a standard weigh-in procedure (i.e., fish are transported to the scale in bags containing water and then weighed in air) and the water weigh-in procedure are being randomly subsampled for the purposes of drawing blood and external radio tag attachment. At the conclusion of the study, we will have drawn blood from approximately 150 largemouth bass subjected to each of the two weigh-in procedures. Blood chemistry assays analyzing lactate, cortisol, and osmolarity will be conducted at Tennessee Tech University .

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Largemouth Bass

We will attach radio tags to about 40 fish from each of the two weigh-in groups. The radio tags have a lifespan of 7 months and are equipped with a mortality switch that will activate if the tag does not move for 12 hours. The tags are labeled with a message offering a $50 reward for returning the tag. Each tag is identified by a unique radio frequency between 30.001 and 31.999 MHz. Tagged fish will be tracked immediately upon release, four days in the first week, and three times in the second week to determine their status as dead or alive. The locations of tagged fish will be determined using a GPS unit and a GIS database will be created in order to determine dispersal patterns.

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The blood chemistry of bass will be compared between the two weigh-in systems using analysis of variance models. The relationship between delayed mortality, blood chemistry, and environmental variables will be examined using stepwise multiple logistic regression models. Ideally, our findings will allow us to predict the subsequent survival of tournament-released fish based on a few simple blood parameters. Such knowledge would be useful in evaluating the efficacy of the water weigh-in method compared to standard weigh-in techniques at tournaments throughout the southeastern United States .

Suggested Reading

Bennett, D.H., L. K. Dunsmoor, R. L. Rohrer, and B. E. Rieman. 1989. Mortality of tournament-caught largemouth and smallmouth bass in Idaho lakes and reservoirs. California Fish and Game 75: 20-26.

Edwards, G. P. Jr., R. M. Neumann, R. P. Jacobs, and E. B. O'Donnell. 2004. Factors related to mortality of black bass caught during small club tournaments in Connecticut . North American Journal of Fisheries Management 24: 801-810.

Hartley, R. A., and J. R. Moring. 1995. Differences in mortality between largemouth and smallmouth bass caught in tournaments. North American Journal of Fisheries Management 15: 666-670.

Neal, J. W. and D. Lopez-Clayton. 2001. Mortality of largemouth bass during catch and release tournaments in a Puerto Rico reservoir. North American Journal ofFisheries Management 21: 834-842.

Schramm, H. L., Jr., P. J. Haydt, and K. M. Portier. 1987. Evaluation of prerelease, postrelease, and total mortality of largemouth bass caught during tournaments in two Florida lakes. North American Journal of Fisheries Management 7: 394-402.

Suski, C. D., S. S. Killen, S. J. Cooke, J. D. Kieffer, D. P. Philipp, and B. L. Tufts. 2004.

Physiological significance of the weigh-in during live-release angling tournaments for largemouth bass. Transactions of the American Fisheries Society 133: 1291-1303.

Suski, C. D., S. S. Killen, M. B. Morrissey, S. G. Lund and B. L. Tufts. 2003. Physiological changes in largemouth bass caused by live-release angling tournaments in southeastern Ontario. North American Journal of Fisheries Management 23: 760-769.

Taylor, J. B. 1990. Delayed mortality and physiological stress responses in tournament-caught largemouth bass ( Micropterus salmoides ). MS thesis, The University of Tennessee , Knoxville .

Wilde, G. R. 1998. Tournament-associated mortality in black bass. Fisheries 23(10): 12-22.



J. Percy Priest Reservoir with Elm Hill Marina complex outlined in the northwest and Fate Sanders Marina complex outlined in the southeast portion of the reservoir.



Two bass released from Elm Hill Marina, coordinates for fish one are designated by a circle and the coordinates for fish two are designated by a triangle. Numbers represent days after tournament release.



Two bass released from Elm Hill Marina, coordinates for fish one are designated by a circle and the coordinates for fish two are designated by a triangle. Numbers represent days after tournament release.