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Delayed Mortality of Tournament Caught Largemouth Bass

GENE GILLILAND (Oklahoma Fishery Research Laboratory, 500 E. Constellation, Norman, Oklahoma 73072)

The Oklahoma Fishery Research Laboratory (OFRL) began a two-year project in spring 1995 to determine delayed mortality rates of largemouth bass following tournament release. Three tournaments in the spring and two in the summer were monitored. Fish were held in large live-nets placed in marina boat stalls after weigh-in. Up to 30 tournament bass per net were held for six days after each contest along with control fish collected by electroshocking. Dissolved oxygen and temperature were measured in the nets and in contestant’s boat live wells as they came to shore.

Spring tournament total mortality (initial + delayed) was less than 6%. Spring water temperatures average 63°F and live-well oxygen levels averaged 7.3 ppm. In the summer, we recorded less than 7% initial mortality. However, after six days we experienced an average of 39% delayed mortality. Most of the fish died between the third and sixth day after weigh-in. High water temperatures (average of 80°F) and low oxygen levels in boat live wells (minimums of 1.3 ppm) were measured. At one summer tournament fish were separated according to oxygen in boat live wells, one group from ‘‘low-oxygen’’ live wells (<6.0 ppm) and another from ‘‘high-oxygen’’ live wells (>6.0 ppm). Fish in the low oxygen group experience a 51% delayed mortality rate while the fish in the high-oxygen group had only a 35% delayed mortality rate. Boaters that ran their aerators continuously rather than relying on a timer had better oxygen levels in their live wells and 16% lower mortality.

The second year of our mortality study (1996) will test procedures that have been recommend by other researchers to see what Tournament Directors and anglers can do to reduce summer mortality.

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For More Information Contact:

Gene Gilliland
Oklahoma Chapter of the American Fisheries Society
Oklahoma Fishery Research Laboratory
500 E. Constellation, Norman, Oklahoma 73072

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Copyright © 1996 Texas Chapter of the American Fisheries Society
Last modified: 03/08/07 01:08 PM