Study sheds light on trout mortality

Courtesy of Centre Daily Times by Mark Nale

Study sheds light on trout mortality

Every angler bringing in a tagged trout was interviewed about bait or artificial used, hook size and type, time caught and other factors. Numbered tags allowed the researchers to keep track of the trout throughout the study. - Mark Nale For the CDT

Every angler bringing in a tagged trout was interviewed about bait or artificial used, hook size and type, time caught and other factors. Numbered tags allowed the researchers to keep track of the trout throughout the study. – Mark Nale For the CDT

If you are a trout angler, at some point you likely learned that trout caught while bait fishing often die after they are released.

Biological studies from the 1950s, 1960s, 1970s and early 1980s reported variation in the mortality of bait-hooked trout ranging from 5 to almost 80 percent. For some bait fishermen, this became a reason for creeling their fish. After all, they would probably die anyway.

For others who developed a conservation ethic, it seemed to be a sound reason to switch from fishing with worms, minnows or salmon eggs to using lures or flies. Research indicated that trout caught using these artificials had a much better chance of survival if released. A hooking mortality of less than 10 percent was reported in the studies.

Using that same logic, fisheries managers across the United States limited catch-and-release and delayed harvest areas to flies or artificials only. For example, in Pennsylvania, we have five different special regulation types based on this thinking: Catch and Release Fly-Fishing Only, Catch and Release Artificial Lures Only, Trophy Trout Artificial Lures Only, Delayed Harvest Artificial Lures Only, and, new this year, the eight Keystone Select Stocked Trout Waters.

“Prior to 1985, the vast majority of fisheries managers would have considered bait fishing incompatible with catch and release regulations,” noted retired fisheries research biologist Bob Carline, who spent much of his career with the U.S. Geological Survey Cooperative Fish and Wildlife Research Unit at Penn State.

However, according to Carline, newer research is slowly changing these attitudes by showing that trout mortality from bait fishing is not very different from the mortality attributed to flies or artificial lures.

“The list of stream studies showing a much lower mortality from bait fishing is growing,” Carline said. “Trout research in Connecticut, Wisconsin, Idaho and, just last month, a new Maryland study on bait hooking mortality with native brook trout was released.”

A 1989 study on flowing water in Connecticut’s Farmington River documented a 10 percent mortality for bait-caught trout. An early 1990s Idaho study on Badger Creek found 16 to 18 percent mortality. In 2004, research done on the Little Brule River in Wisconsin recorded a seven percent mortality for bait-caught trout. The Maryland study, just published in the North American Journal of Fisheries Management, showed only a two percent mortality with bait-caught native brook trout.

Three years ago, Carline teamed up with the organizers of the annual Bald Eagle Creek Trout Tournament to study trout hooking mortality right here in Centre County. The Bald Eagle tournament has catch-and-release regulations — registered anglers must bring their trout in alive in order to collect prizes.

Based on casual observations during the years, Mark Jackson, one of the tournament founders, thought that the hooking mortality associated with the tournament was much lower than previously-published studies.

“Great wild trout fisheries exist on Penns Creek, the Little Juniata River and Spring Creek, and they all allow bait fishing,” Jackson stated. “Based on my own bait-fishing experiences and our tournament results, I had trouble believing that bait hooking mortality caused even a 25 percent mortality, let alone 80 percent. A few trout die as a result of our tournament, but I didn’t think that it was anywhere near 25 percent. Bait anglers who carefully release their trout experience the same low mortality as those fishing flies or spinners.”

The opportunity for a local research project piqued Carline’s interest and he agreed to design a study around the tournament. Observations were made and a study protocol was written in 2013. Data was collected in 2014 and 2015. The final year of the study will occur later this month.

To date, 805 bait-caught trout have been part of the study. Anglers were interviewed with respect to variables that Carline thought might influence hooking mortality. These included trout species, barbed versus barbless hooks, holding method and length of time held, fishing method, hook type, size and other specifics. Almost 75 percent of the tournament trout were caught on mealworms, wax worms, minnows and Powerbait.

“In both years of the study, a total of only 40 trout died of handling and hook injuries. Thirty-seven of these fish were caught on natural bait and Powerbait, while three were caught on artificial lures,” Carline explained. “Trout that were deeply hooked — and the line was cut — were three times more likely to die than were trout without embedded hooks. Fish with blood in the holding water — characteristic of deep hooking — also had a higher probability of dying.”

Tagged trout were held for a nine to 10-day observation period following capture. Even though study trout were subjected to a much higher stress level than trout in a typical catch-and-release situation, the mortality for bait-caught trout was 5.4 percent in 2014 and only 4.1 percent in 2015. A primitive necropsy was performed on the trout that died, looking for specific internal damage and/or the presence of an imbedded hook.

“It is interesting to note that almost all of the trout that died did so during the first 24 hours after capture,” Jackson said. “Many fly anglers believe that trout caught on bait might swim away, but often die a few days later. Only one percent of the bait-caught trout died during days 2-9 of the nine-day observation period.”

Carline detailed the significance of the Bald Eagle Creek study.

“Our study used regular, average anglers fishing with the method that they thought would be most productive. I think that this, along with the total number of trout studied, are the strengths of the Bald Eagle Creek study.

“The important message to be taken from our research and other recently-published studies is that the hooking mortality from bait fishing can be rather low,” Carline added. “The key to low hooking mortality is angler behavior. If bait anglers fish with a tight line and set the hook immediately upon detecting a strike, the fish will not be deeply hooked. Deep hooking has been shown to increase mortality.”

Even requiring the use of barbless hooks or limiting anglers to single-hooked lures might be unnecessary.

“Over 97 percent of the people who caught tagged trout in our tournament used barbed hooks — including double and treble hooks — and we still had a very low mortality,” Jackson said. “This study and other recent research demonstrates that there is no scientific basis for excluding any segment of the angling public from specially-regulated trout waters.”


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