“Bass tend to abandon their nests due to the physiological stress of being caught,” he says. “Other scientists have taken detailed physiological measurements and found the bass truly exhausted. Nest abandonment was high.”

Those studies were cooperative ventures by researchers working with the Illinois Natural History Survey, the Ontario Ministry of Natural Resources, and the Queen’s University Biological Station. The biologists selected a series of lakes and rivers in southeastern Ontario, near the Ontario-New York border where the bass season is closed in spring, but the season for other species is open. They wanted to assess the effects of preseason catch-and-release angling on the reproductive success of largemouth and smallmouth bass.

In one of the lakes (Lake Opinicon) as many as 63 percent of anglers were observed targeting nesting bass under the guise of fishing for another species—typically crappies, walleye, pike, or perch. When the researchers went underwater and counted the number of bass with visible hook wounds, they found that in the most heavily targeted lake, almost 100 percent of the nesting males had been caught and released. If the bass season had been opened, every single nesting male possibly could have been harvested.

But the season was closed so the researchers turned their attention to determining if the illegal catch-and-release fishing they’d observed affected the spawning success of the bass population? It did, they say, in a major way.

In the lakes and rivers that received the most preseason angling, spawning success was the lowest. Fewer than half the bass nests were successful. But in the lakes and rivers where catch-and-release angling for nesting bass was minimal, 84 percent of the guarding males successfully raised a brood.

A relationship also appeared between the time it took a male bass to return to its nest after being caught and released and the rate of nest abandonment. When a groggy bass took more than 10 minutes to return to its nest, the eggs and fry were preyed upon more than 90 percent of the time and over 90 percent of the nests were abandoned. Even when males returned to the nest in two to five minutes, more than half the nests eventually were deserted.

Ontario Ministry of Natural Resources biologist Barry Corbett, who recently completed an extensive multiyear smallmouth bass tracking study on Lake of the Woods, reported seeing the same thing. In order to surgically implant radio transmitters inside a number of bass, Corbett waited until the males were guarding nests. When he dove below to net a fish, he says he was shocked to see two things: The number of males with hook wounds and the number of the exotic rusty crayfish harassing the bass.

“It was like a scene out of the movie Aliens,” Corbett says. “So many crayfish were surrounding the nests, waiting for a chance to gobble up the eggs, that we had to leave a technician underwater to protect the site, while we placed the transmitter inside a bass and then returned it to the nest.”

“Aliens from above and aliens from below,” say the Canadian and American researchers. “Illegal preseason angling of nesting bass,” they concluded, “even on a catch-and-release basis, appears to be detrimental to overall fry production and survival because of an increase in brood predation and male nest abandonment.

“And we should never forget,” cautions Ridgway, referring to the paltry 30 percent of male smallmouth that are preselected to spawn each season, “that no more bass are waiting to move onto the nests.”

*Gord Pyzer, Kenora, Ontario, is a field editor for In-Fisherman magazine. Formerly a senior manager with the Ontario Ministry of Natural Resources, he now operates a fishing and deer hunting guide service on Lake of the Woods. Contact Gord at 807/468-4898 or .