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Why We Fish

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I knew that I couldn’t stop the fish, no matter how skillfully I played it. I waded out into the water as far as I dared, knowing as I did so that it was a pointless gesture.

But then the miraculous occurred, just as I looked down at my reel to see all of the line gone except for the knot.

Excerpt from Why We Fish.


'Fisheries-Induced Evolution' Could Make Bass Tougher To Catch

Following what is believed to be the first research to look at fish stress as it relates to angling success, scientists have some bad news for bass fishermen.

"We could potentially be selecting for fish that are harder to catch," said Cory Suski, University of Illinois natural resources and environmental sciences professor, who conducted the investigation, along with Illinois Natural History Survey research scientist Jeffrey Stein and graduate student Michael Louison.

Over time, as the bass within a population willing to bite are diminished by anglers who keep their catch and/or delayed mortality, "fisheries-induced evolution" could occur, leaving behind a larger percentage that are not. Commercial harvest of the only the largest fish in a species provides an example of how that happens.  Eventually, fish predisposed not to grow as large dominate and average size declines.

Before this research on bass, most studies of fish vulnerability have focused on personality traits, such as boldness and aggression. This one looked at levels of stress hormones and how they related to a fish's reaction to presentation of a bait.

"When it encounters a challenge or novel situation, a fish's adrenaline shoots up, and that individual is more likely to attack or run away," Louison said. "But if an animal shows a relatively high cortisol response and a low adrenaline response, they're more likely to freeze."

Based on a study of 113 largemouth bass for boldness and stress response, those that freeze are the least likely to bite. For the boldness test, researchers looked at how often each fish left a refuge area of a tank and ventured into the open. For the stress test, they took blood samples, exposed the fish to the open air for three minutes, and then returned them to the tank, where they recovered for a half hour before a second blood sample was collected.

The researchers compared cortisol levels in each fish before and after the air-exposure challenge. A separate trial measured the fish's metabolic rate.

They then released the fish into a small pond and commenced seven days of two-hour angling trials, using a variety of lures. They found no correlation between a fish's metabolism or willingness to explore and its likelihood of being caught. But they did see a substantial association between stress-related cortisol levels in the fish and their likelihood of being captured by angling. Post-stressor cortisol concentrations were 48 percent higher in the fish that were never caught than in those that took the bait.

The researchers cautioned that their findings so far apply only to one species under a special set of conditions. Other species may respond differently.

"The ultimate question that we're trying to ask is, 'Why do fish hit a fishing lure?'" Suski said. "We tested a lot of mechanisms that could potentially explain this behavior, and we saw that hormonal response was the main driver."


Florida Bass Fingerlings Receive Survival Training

Because of unique survival training that they received as fingerlings, more stocked bass are reaching catchable size in Florida's waterways.

"Previously, fingerlings went from indoor ponds, where they had food dropped in to them, to lakes," said Nick Trippel, a fisheries biologist with the Florida Fish and Wildlife Conservation Commission (FWC). "They didn't know to run from bigger fish and birds."

As a consequence, telemetry studies using radio tags the size of a grain of rice revealed that survival rates for stocked bass at Lake Carlton on the Harris Chain was far lower than for fish spawned in the wild. Researchers discovered that hatchery bass tended to wander away from cover more often than wild bass. Failure to avoid predators, including birds, was apparent from the tags that turned up on shore under nests, in neighboring Lake Beauclair, and even inside a live double-crested cormorant.

"Hatchery fish didn't know how to use habitat or run from predators," Trippel said. "Wild fish knew to hunker down."

Also, study of fingerlings in experimental ponds, "with everything found in real lakes," showed that most mortality occurred within two weeks of stocking.

So biologists from the Eustis Fisheries Research Laboratory teamed up with researchers at the Florida Bass Conservation Center to see if they could educate young bass about the dangers of life in the wild. Turns out, they could.

"For conditioned fish, the survival rate was 60 to 65 percent," Trippel said. "It had been just 30 percent for naive fish."

Researchers educated the bass by moving them from indoor tanks to outdoor ponds 10 days before stocking. Plus, they added seven mature bass and seven bowfin to each pond.

"We wanted the fish to see their brothers and sisters eaten and know there was danger," the biologist said.

By contrast, fingerlings moved to outside ponds with no predators managed only 35 percent survival. Exposure to predators seemed to make the big difference.

Following that success, biologists tried adding mature bass to indoor tanks, which had habitat for the young bass to hide it. That type of conditioning improved survival as well.

Also, the number of fingerlings lost during conditioning was minimal in terms of impact to overall production. "Keeping them inside, we lost fish to disease," Trippel said.

Now, FWC is working on incorporating these strategies into its statewide stocking program.

"We don't have enough ponds to move all the fish outside," the biologist said. "But we can add predators to the raceways inside. Also, it's less stress on the fish because we don't have to move them.

"Right now, we're able to do this with smaller scale stockings."



Secrets From The Headwaters

In general, finding the right locations are more important during summer and winter. That’s because bass tend to school and stay in the same places for days or even weeks during these times. By contrast, lure selection can be more important during spring and fall. Fish roam more then, looking for places to spawn and chasing bait in the shallows.

Find out many more fish-catching secrets like this in my book. Buy at Barnes & Noble or Amazon.