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B.A.S.S. 22y

Keeping Bass Alive

What causes the delayed mortality of tournament-caught bass that appear lively and healthy at release? In a word, stress. Fish constantly expend energy to maintain body conditions within certain tolerable ranges necessary for survival. Although fish are cold-blooded and do not have to maintain body temperature, they still expend energy to supply oxygen to their
tissues, eliminate waste products, process energy reserves, repair damage, secrete mucus, fight disease, and maintain proper concentrations of salts in the body fluid.

In the spring, considerable energy is also diverted to spawning and nest guarding.

 

15 stress factors


1. Hooking
2. Playing
3. Landing/handling
4. Air exposure
5. Livewell
6. Culling
7. Bagging/handling
8. Staging tanks
9. Judging tray
10. Weighing process
11. Transport from weigh-in
12. Salt-dip
13. Release holding tanks
14. Release handling
15. Release environment


When conditions deviate from normal, the fish channels its energy to appropriate organs and tissues to restore normal conditions. Each of these situations is a stressor.

Cortisol and similar hormones trigger the production of energy to alleviate the stress. Hormone levels and physiological functions return to normal within three to five days after the stress is alleviated. But when multiple sub-lethal stresses occur in a relatively short time period, enough energy to fight them and still maintain normal body functions may not be available.

Generally, delayed mortality is a result of prolonged water-salt (osmotic) imbalance — salt concentrations in body fluids drop below the levels necessary for survival. We will describe techniques to greatly reduce this stress.

Stress Reduction

Reducing stress, and thus reducing delayed mortality, requires three things: 1) reducing handling injuries and loss of protective mucus, 2) healthy conditions in the boat livewell, and 3) quick, efficient weigh-ins where fish are subjected to minimal handling while maintained in adequate life-supporting conditions throughout the weigh-in.

Anglers should be aware that simply holding several fish in a livewell adds stress even when the livewell provides otherwise healthy conditions for the bass. Research has shown that the heart rate and oxygen consumption of a single smallmouth bass caught and placed alone in a livewell returned to resting cardiac output levels in about an hour. On the other hand, when two or more fish were caught and placed in the livewell, cardiac activity remained high, even after six hours.

Handling is a stressor. If you consider how many times a tournament bass is handled from the time it is caught until it is released, handling can be a significant source of stress. Every time a fish is handled — especially if it tries to escape the angler's grasp, bounces on the boat deck, or becomes active when being measured or weighed — its metabolism increases, its heart rate increases, and it needs more oxygen.

Research has now shown that simply exposing fish to air is also stressful. The point here is that while some handling is unavoidable, it should be kept to a minimum, and fish should not be exposed to air any longer than is absolutely necessary.


Why bass die — initial and delayed mortality

  • Injury

  • Water temperature

  • Dissolved oxygen

  • Water quality

  • Stress (You are here)

  • The angler's role in improving survival of released bass (Next chapter)

    Table of contents


    Hard copies of Keeping Bass Alive are available for $3.00 each, please contact the Conservation
    Department at (334) 272-9530 ext. 404 or conservation@bassmaster.com.

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