Pond Boss Forums INTRO Questions & Observations Is Fast Bass Growth Optimal?

IS FAST BASS GROWTH OPTIMAL?

Long Term Bass Research – Much of the support for stocking Florida-strain bass is based on studies suggesting that young Floridas grow faster than northern-strain largemouths. There is evidence that more fast-growing and thus larger fry survive their initial winter. But there has been little evidence, other than the capture of huge pure-Florida and F1 hybrid largemouths from select superior bass habitats, to suggest that fast growth translates into greatly increased production of larger bass.

A Texas Parks ad Wildlife report provides insight into the relative long-term importance of fast and slow growth.* In 1985, Texas biologists bred two pure Florida largemouth, then separated the fastest and slowest young bass into two 400-bass groups. The groups were stocked and maintained with adequate food supplies in separate but equal pond habitats with yearly growth and condition recorded for 17 years. The number of bass in each group was reduced as bass grew, food requirements increased, and natural mortality occurred.

Three years after the experiment was started, bass were given electronic tags so records could be maintained. This allowed stocking a pond with 50 fish from each growth-rate group and 50 from a control group that grew at average rates, so variations in pond habitats would not affect comparisons. The sex of each individual was identified at age 6 (1991) during a spring examination, so growth differences related to sex could be identified.

Slow-growing bass fry lived longer than their fast-growing siblings. Under these experimental conditions, slow growers did not die during the first two winters at rates much different from fast growers. In fact, between age 1 and 2, fast growers had high mortality (31 percent) than slow growers (16 percent).

In 2003, when a cut in funding required the report to be written, 13 slow growers had survived (lived 17 years). Only two fast-growing females remained. Of the slow growers, seven were females and six males. Mortality had varied between 2.5 and 34.0 percent over the initial 4 years, but by age 5, mortality was less than 5 percent for these mature adult bass living in controlled habitats, with ample forage and no angling losses.

By age 9, mortality rates again varied from 5.0 to 34.0 percent yearly, while 16-year old fish had 26 to 31 percent annual mortality. This suggests that aging lunker bass released by anglers may have at least a 60 percent chance of surviving another year.

Mortality was related to sex, with females more abundant than males each year. Male mortality has been attributed by biologists to stresses associated with spawning and guarding fry. At age 6, only 33 percent of 119 surviving fish were males, and from age 7 though age 12, males accounted for 24 to 33 percent of the survivors. But males were 37 percent of the surviving population at age 13 and averaged about 41 percent for ages 14 through 17; so male losses decreased proportionally after age 12. After the initial growth differences that allowed separation into groups, average growth rate of the fast growers was only slightly more than that of slow-growing bass. The rates of the two groups varied with slow growers enlarging faster in some years than the fast-growing group. At ages 13 and 15, the two largest bass were 24-inch-long females from the slow-growing group.

As with the comparisons of length increments, fast growers gained weight fast growers gained weight only slightly faster than the slow-growing group. But after age 6, individual bass from both groups varied widely in weight. Twelve test bass, 5 fast and 7 slow growers, exceeded 8.8 pounds at some point in their lives. In 1998 at age 13, the heaviest bass was a slow-growing female weighing 11.2 pounds. A fast-growing female weighing 10.8 was a runner-up. Some males remained relatively small throughout the study, with one slow grower at age 15 weighing 3.3 pounds.

The author concludes that categorizations such as fast growing or slowing growing (young-of-the-year) failed to predict subsequent growth. Slow growers survived as well and appeared to live longer than fast growers. Although only two parents contributed to the gene pool, there were great variations in the growth, weight gain, mortality, and longevity of individual bass. This research suggests that some assumptions need to be further evaluated over the long term.

Robert Manns

*Howells, R.G. 2003. Comparison of initially fast and slow growing sibling largemouth bass through age 17. Management Data Series No. 210, Texas Parks and Wildl. Dept., Austin.