Fishing Factors to Calculate Trout Mortality

Interesting study on trout mortality (based on differing catch & release scenarios) posted on denverpost.com today.

Fishing Factors to Calculate Trout Mortality
Charlie Meyers, The Denver Post
Posted: 06/10/2009 01:00:00 AM MDT


To illustrate the likelihood of postrelease trout mortality, the Colorado Division of Wildlife produced a program illustrating what happens when certain factors come into play. These elements include severity of hooking injury, length of fight, size of fish, time out of water and water temperature. No distinction was made between flies or lures. All calculations were made for an 18-inch trout. Here are a variety of scenarios and the projected percentage of mortality:

Flies and lures

1. 60-degree water temperature, superficial hooking, playing time 4 minutes, 1 1/2 minutes out of water. 10 percent probability of dying.

2. All the same elements, but with 70-degree water. 17 percent probability of dying.

3. 60-degree water, superficially hooked, playing time 2 minutes, 1 minute out of water. 5 percent probability of dying.

4. 70-degree water, superficially hooked, playing time 2 minutes, 1 minute out of water. 8 percent probability of dying.

5. 60-degree water, playing time 2 minutes, no time out of water. 3 percent probability of dying.

6. All elements the same except 70-degree water. 5 percent probability of dying.

7. 60-degree water, playing time 4 minutes, other elements the same. 5 percent probability of dying.

Bait

1. 60-degree water, playing time 4 minutes, 1 1/2 minutes out of water, superficially hooked. 22 percent probability of dying.

2. All the same elements, except a deep hook set, leader was cut. 42 percent of dying.

3. All the same elements, except the leader was not cut. 66 percent probability of dying.

4. 70-degree water, superficially hooked, playing time 2 minutes, 1 minute out of water. 17 percent probability of dying.

"This illustrates that if you reduce the playing time in half at 70 degrees, you reduce the probability of dying by more than half when fishing with artificials," DOW biologist Jeff Spohn said. "Playing time and the time kept out of the water clearly are the most important elements in keeping fish alive."

Read the Denver Post article here:
http://www.denverpost.com/extremes/ci_12556903

Also, a secondary (& longer) article about mishandling of fish on Antero Reservoir:
http://www.denverpost.com/extremes/ci_12556902

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