Ask a bass angler after a subpar fishing trip what they think management needs to do to improve the fishing, and the answer almost always will be “stock fish.”
There are good reasons to stock bass. Certainly, you need to stock bass into a new or renovated farm pond to establish a new population, and some significant benefits have been realized by stocking Florida largemouth bass into northern largemouth bass populations to increase trophy fish potential. But study after study has shown that stocking largemouth bass into existing bass populations to increase the number of bass does not work.
A variety of factors can affect the survival of the stocked bass, but the most important factor usually is predation by other bass. Since losses to predation are size-dependent, and large fish are less vulnerable to predators than small, it would make sense that stocking larger bass might improve survival and stocking success.
A recent study by Illinois Natural History Survey fishery scientists rigorously evaluated the effect of size of stocked largemouth bass on survival.
Four Central Illinois lakes were each stocked with four sizes of largemouth bass:
• small fingerlings (2 inches long) stocked in July at
50 fingerlings per acre;
• medium fingerlings (4 inches long) stocked in August
at 25 per acre;
• large fingerlings (6 inches long) stocked in September
at 12 per acre; and
• advanced fingerlings (8 inches long) stocked in
May of the subsequent year at 6 per acre.
All fingerlings were spawned and reared to stocking size in the hatchery. The advanced fingerlings were held and fed in the hatchery over the winter and stocked the next spring.
Fish held in cages in the lakes for 48 hours after stocking indicated mortality related to transportation and handling was less than 6 percent and did not differ among sizes.
Electrofishing during the fall was used to monitor the survival of the stocked bass. During the first fall (advanced fingerlings had not yet been stocked), electrofishing catch rates of the large fingerlings were higher than the catch rates of the small and medium fingerlings. During the second year, these differences vanished, and there was no significant difference in catch rate among the sizes, including the advanced fingerlings. There also was no significant difference when catch rate was adjusted for the number stocked.
OK, size at stocking did not significantly affect survival, but what were the contributions of the different fingerling sizes to survival. The greatest catch rate was for the advanced fingerlings, and it was less than two fish per hour electrofishing the fall after they were stocked.
Is this significant? I’m certain that there are some anglers out there that think along the lines of, “well, that’s two more bass to catch, right.” They are correct, but let’s work through some simple math that ends in your wallet and the services MDWFP can provide for you.
First, the advanced fingerlings sampled by fall electrofishing had grown to about 9 inches long. The researchers did not report the electrofishing catch rates for all largemouth bass, both stocked and Nature’s own, so I have to do some estimating. Fall electrofishing catch rates in small impoundments average around 100 bass per hour, and about half or more of those fish — about 50 fish — would be 8- to 10-inches long. Those two advanced fingerlings per hour electrofishing would represent between a 2- to 4-percent increase in the abundance of that size class of bass.
A typical, fertile small impoundment, as occurs throughout most of Mississippi, will support about 50 pounds of bass per acre. Of this, about 10 pounds per acre will be 8- to 10-inch bass, or about 20, 8- to 10-inch bass per acre. Two to four percent of 20 bass per acre is less than one bass per acre, specifically about 0.4 to 0.8 bass per acre.
The advanced fingerlings cost $4.05 per fish to raise and stock and, at a stocking rate of six per acre, stocking would cost about $24 per acre per year. Stocking a 500-acre lake with advanced fingerlings would cost $12,000.
A Mississippi resident freshwater fishing license costs $8. It would require dedicating the license revenues from 1,500 anglers to increase the abundance of 8- to 10-inch largemouth bass by 2 to 4 percent in this 500-acre lake. Lakewide, the number added by stocking would be 200 to 400 bass, or approximately one-eighth to one-quarter bass for each of those 1,500 anglers that footed the bill to stock the fish.
By the way, even at $4 per advanced fingerling, those bass come with no guarantee that they will survive to 12 to 14 inches, or larger, and will be caught.
Yes, the stocking could be done more cheaply using higher densities of less-expensive medium or large fingerlings, but the outcome would be approximately the same.
Is it worth it to stock fingerling bass into an existing bass population? I’ll let you answer the question. It cost $24 per acre to stock advanced fingerlings, and the return was a couple fish per acre. Is that how you want to spend your license dollars?
I know of no lakes, reservoirs or rivers in Mississippi that support largemouth bass that lack natural reproduction. If you continue to think stocking bass into existing bass populations is good management of both fish and financial resources, do the math for 58,000-acre Sardis Reservoir.
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