Study: Time out of water endangers the nests of bass

Springfield, Ill. — Bass anglers have embraced catch-and-release fishing over the past two decades, a commitment to conservation that can pay off with future catches of bigger fish.

But the practice may come with a catch, so to speak.

Researchers say that anglers concerned about bass populations in their favorite fishing holes should cut down on the time between the moment they catch a largemouth bass and the time they release it, especially during the early part of the fishing season. A recent University of Illinois study revealed that catch-and-release anglers who spend too much time admiring their catch of a male bass may give bass predators a window to invade a largemouth nest and eat young bass the adult male was protecting.

Fisheries biologists have long asserted that female largemouths abandon the nest immediately after laying eggs, leaving the male bass to defend the nests from predators.

In essence, time spent away from the nest during a catch-and-release event and the subsequent exhaustion it causes the male are critical to the survival of the embryos, particularly in lakes with high densities of brood predators, the study claims.

The number of fish that feed on young largemouths – primarily bluegills, pumpkinseeds, or rock bass – in a lake plays a big part in the equation.

“One of the main conclusions was that in a lake where there are very few brood predators, when you angle a male away from his nest and then immediately release him, the chance of a negative impact is less, but if the nest is located in a part of a lake where there is a high density of brood predators, once the male is removed, predators get into the nest very quickly,” said Jeff Stein, a senior research scientist with the Illinois State Natural History Survey and an adjunct professor at the U of I.

What is the ideal catch-and-release time window?

“On average, the time it took brood predators to begin eating bass young was less than five minutes in cases where the nest was located near schools of brood predators,” Stein noted.
In the U of I study, 70 nests were located within nine lakes with natural largemouth bass populations. The numbers of known brood predators in each lake varied. Stein snorkeled in shallow water and observed the nests. He assigned scores representing the number of brood predators and the quality of parental care demonstrated by the largemouth bass males.

As part of the study, nesting males were captured and held in a livewell for 15 minutes, then released. According to Stein’s records, it took an average of 30 minutes for the male bass to return to their nests.

Tactics used by catch-and-release anglers came into play for the researcher. He analyzed the habits of various types of fishermen.

“A pro who isn’t interested in anything about the fish other than that he caught it will rip that fish in about 15 seconds into the boat and spend only about another minute or two with the fish before releasing it back into the water,” Stein said. “Casual recreational anglers may be afraid they’re going to lose the catch and so may play it a little more, which exhausts the fish more. After the fish is caught, it might accidentally flop around on the floor of the boat for a while. They may put it in a livewell if they’re thinking of keeping it or until they get the camera out. Five minutes or more elapse.”

When finally released, male bass are disoriented, “so they go to the bottom to sit and recover for a while and get their heart rate back to stasis,” Stein said. “The fish is saying, ‘OK, I lived through whatever that was. Now where is my nest?’ and by the time it actually gets back to the nest it has been gone from it 30 minutes.”

Most concerning to bass fans is the assertion by Stein that delayed catch and release eventually has an effect on largemouth populations – especially in smaller lakes.

Bass typically spawn only one time per year. Stein contends that if the male bass loses the nest’s eggs, it’s unlikely another spawn will take place.

“In a lake with 100 bass nests but very little angling pressure and not many predators, one, two, or three nests where the male gets captured and the nest is raided won’t make a big difference in the overall population flow because most of the first-year young are going to survive,” Stein said. “But in a smaller lake with lots of bluegills and lots of anglers throughout the spawning season, that scenario could affect the next generation of bass.”

As far as fishing spawning beds for bass, Michigan has no restrictions other than season dates and catch-and-immediate-release mandates during the early season.

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