The wobbling pull of the big crankbait stalls suddenly, and as the angler raises his rod, there’s a strong thumping pull 20 yards out and 18 feet down. After several runs, the bass approaches the boat and the angler loosens the drag to avoid pulling out hooks. After leading the fish around the boat carefully, his partner nets the 6-pounder. High fives all around and the anglers decide to weigh the lunker. A few photos are in order. And because the lake is managed with a 22-inch length limit, the measuring board is dug out. Then back she goes, with the anglers in a celebratory mood. But the fish is not feeling as well. It may be days until her metabolism returns to normal, and if her stress response is extended, a deadly disease may attack since her immune system has been suppressed.

Protected slot limits and other length limits are management tools essential to the future of bass fishing in most regions. At In-Fisherman, we’ve long championed selective harvest. But such regulations or decisions to voluntarily release fish only work if released fish survive and prosper. Dr. Bruce Tufts, Professor of Biology at Ontario’s Queens University and an expert on the physiology of catch and release, has pried and probed into the bodily functions and processes of fish and has carefully monitored how they react when we hook, fight, photograph, and set them free. In-Fisherman Field Editor Gord Pyzer, a fishery biologist himself, sat down with Tufts to review his key results.

“To maintain high-quality fisheries,” Tufts says, “we have to be selective of the fish we keep. In some waters, we’re already catching the same fish several times a year. A released fish must be able to quickly return to normal behavior—feeding and avoiding predators. Also, seriously stressed fish are more susceptible to disease.”

Tufts and his colleagues have made major discoveries involving catch-and-release angling in recent years. What they’ve observed bodes well for the future, but only if anglers heed the information and practice careful catch and release.

Counting Casualties

“In the early days,” Tufts explains, “information about catch and release came from studies that simply counted dead fish after they were caught, handled, and released under various conditions. Though limited in scope, these studies demonstrated to many skeptical anglers and some fishery managers that most bass and other species survive when released. But much biological information was missing.

“As with humans, fish can be in pretty rough shape, but still be alive. Today, we have considerably more information, obtained through physiological studies, to determine what goes on inside a fish when it’s caught and released. We’ve monitored many physiological variables and assembled a picture that tells us the condition of the fish after a disturbance like being caught.

“When a medical doctor needs to diagnose a disease,” Tufts explains, “he first takes a blood sample and analyzes it. In the hospital, an intravenous cannula is implanted in your arm to take samples anytime. We do the same with fish, surgically implanting tubes in blood vessels to determine how the fish is doing.

“We may also surgically implant tiny transmitters to monitor heart rate and muscle contractions. Sometimes we need to obtain physiological information from other tissues, which involves terminal sampling after the fish has been killed with anesthetic. We often use a combination of strategies to get a complete picture of the physiological response to angling under certain conditions. We keep conditions constant except for one particular factor, such as angling time, fish size, or water temperature.”

Fight Or Flight

Tufts says the first things that happen inside a fish when we hook it are similar to what takes place inside us when we realize we’ve hooked it. The initial physiological changes involve what he calls a “hormonal axis” commonly known as the “flight or fight response.”