Catch and Release Mortality

[Bear742]

Since the original discussion on the reader's voice forum in November, I came across an interesting report on Catch and Release mortality.

Believing firmly that Murphy was an optimist, I have always had the nagging belief that not all live released fish survive. However, putting a number on the mortality rate has always been the problem. Obviously I was happy to see a research based article on the subject.The whole article was in North American Fisherman. Unfortunately I could not find a way to link to it. Here are some highlights from the article.

RESEARCH UPDATE
"Handle With Care", by Dr. Hal Schramm, North American Fisherman, Dec-Jan 2012 p.16

The author draws information from this article, Risley, C.A.L., and J. Zydlewski. 2010. "Assessing the effects of catch-and-release regulations on a brook trout population using an age-structured model." North American Journal of Fisheries Management 30:1434-1444

"Memories and embellishments aside, I think there is good biological evidence to support the contention that, indeed, some fishing isn't as good as it used to be. Let me share an example for brook trout fisheries based on some population modeling done by Maine fisheries scientists.

"Good brook trout fisheries," those with numbers of fish larger than 12 inches contain a lot of old fish. Brook trout typically reach almost 8 inches by age 2, 10 inches by age 3, 11 inches by age 4, and surpass 12 inches by age 5. To get old, fish have to escape capture or survive after release.

"There is always some level of mortality, even when fish are handled gently and kept in the water for unhooking. Actual measured rates of post-release mortality for brook trout caught on single-hook flies are 0 to 14 percent, and average about 5 percent. It is considerably higher for actively fished lures, and jumps to about a 32-percent average for passively fished bait.

"As you might expect, the number of larger and older fish declines as hooking mortality increases. When hooking mortality increased from 0 to 14 percent (the range for single-hook flies), the calculated numbers of age 4 and 5 trout declined about 28 percent at low levels of fishing effort.

"Increasing the fishing effort had an even greater effect. With a 5 percent mortality rate, a fishing effort of 400 angler hours per acre per year cut the number of age 4 and 5 brookies in half, compared to no fishing effort and only natural mortality.

"While 400 angler hours per acre may seem high, it really isn't. An acre of brook trout stream may be one-half mile long. And the 400 hours can be reached by only two anglers fishing four hours each per week in the half-mile reach. This and higher levels of fishing effort have been measured in many Eastern brook trout fisheries.

"Brook trout are extremely resilient; and, as the population is reduced, the remaining fish will spawn at younger ages and the offspring will have higher survival rates. Thus, catch rate will tend to remain high, but the fish will be small."

This brings some true light into a discussion which is too often dominated by smoke and wind. I hope you enjoyed it.