By Robert Montgomery: When an angler can see a large bass, but just can’t entice it to bite, he often rationalizes the failure by saying, “Well, it didn’t get that big by being dumb.” He isn’t talking about size, though. He’s implying that the bass gained wisdom through age. In other words: “Big” equals “old.” But in the world of bass, “big” does not equal “old.” In Florida, scientists used otoliths (ear bones) to determine that a 10-pound-plus largemouth was just 4 years old.
By contrast, an angler recently caught and released a 3.5-pound bass in Montana that was judged to be 19 years old, based on a tag inserted 14 years ago, when it weighed 1.5 pounds.
So, a 4-pound bass in Minnesota or Montana might not be impressive in terms of weight, but it could be a real trophy if age is given equal consideration.
Does that mean that bass fisheries in northern waters should be subject to stricter regulations to protect a vulnerable, slow-growing population?
Not necessarily.
That same 4-pound bass could be 6 or 7 years old, instead of 18 or 19. Just as not all Southern bass grow to 10 pounds, not all Northern bass live to 19.
“Very old fish are rarities, just like human beings who live to be more than 100 years old,” said Roy Heidinger, who, before his retirement, studied age and growth in bass for years at Southern Illinois University.
“These old fish are not the bulk of the sport fishery.”
In a Florida study, 822 trophy bass (10 pounds and up) given to taxidermists showed a mean age of 9.7 years. That’s a growth rate of about a pound a year. As previously mentioned, the youngest was just 4 years old, while the oldest, likely from the northern part of the state, was 16.5.
Bass grow large and/or live long because of a variety of variables, including genetics; forage species and abundance; climate and latitude; and type of fishery, its water quality, and habitat. Fish in more northern climates typically live longer, but grow slower and don’t get as big as their counterparts in the South, especially Florida strain bass.
Genetics limit growth of Suwannee River bass to under five pounds.
Also, whether in the North or the South, bass tend to grow their entire lives. Rate of growth slows as the fish age but never stops.
Forage
For maximum growth, a bass must have available and abundant forage of the right size for each stage of its life, said Gene Gilliland, Oklahoma’s assistant chief of fisheries.
“In lakes with high recruitment, unless they are extremely fertile with lots of forage, you’re going to have slow growth because there are too many mouths to feed,” he explained.
A shad diet is better for growth than bluegill, added Wes Porak of Florida’s Fish and Wildlife Research Institute. That’s because shad have higher energy content or “bioenergetic” value.
In other words, bass get more bang for the buck with shad, especially threadfin, for biological maintenance (digestion, metabolism, and activity costs), body growth, and reproduction.
Trout are even better, according to Steve Pagliughi, a consulting fisheries biologist. Writing in the September/October issue of Bassmaster Magazine, he explained how a bass, nicknamed “Dottie,” grew to world-record proportions — 25.10 pounds — before it died in 2008.
Jeb Dickerson with Dottie when she weighed 21-11, just 9 ounces off the world record.
“Take trout out of the equation, and there’s no doubt this fish would not have weighed anywhere near 25 pounds,” he said. “Lake Dixon has been stocked for many years with large numbers of hatchery trout . . .
“Trout have high levels of lipids and protein when compared to more traditional prey.”
By contrast, crawfish aren’t nearly as nutritious. Much of their weight is mostly indigestible shells.
“It’s not just the forage, but how easy it is to capture,” said Porak. “Is it schooling? Can it be ambushed (with little expenditure of energy)? Threadfin and silversides in open water require higher energy to catch.”
Additionally, the scientist said, laboratory observations have revealed that prey capture efficiency declines when plants reach “excessive levels.” That means growth slows as well. Read on….