Bed fishing revisited

Impact on bass stocks is minimal

It’s spawning time for largemouth bass throughout much of Mississippi. It’s time for sight fishing bass on the beds, and it’s prime time for the perennial debate about the effects of bed fishing. I’ve written on this subject before, emphasizing that there is no effect on bass populations in Mississippi’s waters. A new study finally closes the case on the biological effects of bed fishing.

Fisheries researchers have demonstrated that bed fishing can adversely affect the production of fry. The longer a guarding male bass is kept away from a nest, the more predators like bream and shiners are likely to consume the eggs or fry. And the more eggs or fry removed by the nest-robbing predators, the more likely it is that the buck bass will abandon the nest completely, leaving the remaining eggs vulnerable to more predation, lack of oxygen and fungus.

Yes, bed fishing can reduce the production of fry from an individual nest. But it only takes successful reproduction from a few pairs of largemouth to populate a large pond or cove in a reservoir. In Mississippi and other southern waters, far more bass are spawned every spring than the environment can support. There is no evidence — repeat, no evidence — that bed fishing has ever hurt a largemouth bass population in southern waters.

Nevertheless, many anglers still call foul, insisting that bed fishing causes dwindling numbers of catchable bass.

University of Florida fishery researchers Daniel Gwinn and Mike Allen used a population model to identify conditions where spawning-season protection may benefit largemouth bass populations. Like most population models, this one used established values of bass growth, natural mortality, catch and harvest, and recruitment rates to predict changes in the bass population.

However, the model also incorporated new knowledge about the effects of fishing for spawning bass, namely the loss of eggs and fry when females are harvested before they spawn or males are harvested while guarding nests, the prevalence of catch and release (C&R) and hooking and handling mortality of released fish. The model also included functions for density-dependent mortality of young bass, such that survival of young bass decreases when more adult bass produce more offspring.

The models predicted the abundance of adult bass under four different management strategies: a year-round open fishery with a 14-inch minimum length limit (open fishery), a complete closure (no fishing) during the spawn, a C&R fishery during the spawn and a year-round C&R fishery. These management strategies were modeled for northern (low productivity, slow growth, long life span and late maturation) and southern bass populations (fast growth, shorter life span and early maturation).

For bass fisheries typical of those in most Mississippi reservoirs, C&R during the spawn increased the adult bass population 8 percent compared to the year-round open fishery. Spawning-season closure increased the adult bass population 20 percent compared to the year-round open fishery. The greatest increase in adult bass abundance — 42 percent compared to the year-round open fishery — resulted from the year-round C&R fishery. Similar but smaller effects were seen for less productive, northern bass fisheries.

Very different results were seen when the models were applied to lakes where anglers caught a high proportion — 70 percent per year — of the catchable bass population. This condition could occur in Mississippi’s state fishing lakes during the first several years after they open, either as new lakes or after closure for renovation. For these high-exploitation lakes, C&R during the spawn again had the lowest increase in adult bass — only 8 percent — compared to the open fishery. The greatest increase — 45 percent more adult bass than the open fishery regulation — resulted from the spawning-season closure. Year-round C&R resulted in a 38 percent increase in adult bass compared to lakes with an open fishery.

What does this mean for Mississippi’s bass fisheries? For almost all fisheries, C&R during the spawning-season closures will have a minimal effect on bass abundance compared to a year-round 14-inch minimum length limit. Neither anglers nor biologists employing conventional population assessment protocols would be able to detect an 8 percent increase in adult bass.

Spawning season closures would increase the adult bass population enough that anglers would probably see increases in catch rate. In the last few years, several states have lifted long-standing spawning-season closures for black bass, and only one state (Minnesota) retains a closed season for bass. It is a pretty safe bet that Mississippi anglers would not be willing to give up fishing during the spawn to catch a few more bass during the rest of the year.

If anglers really want more bass to catch — a predicted 42 percent more — they need to consider year-round catch and release.