May 2017
From Wildlife and Freshwater Fisheries

Lake Guntersville: Perception vs. Reality

Many believe Lake Guntersville is on the decline, but is it?

  Growth rates of Guntersville’s largemouth bass are exceptional.

For the first time in my tenure as director, the Conservation Advisory Board meeting March 4 was not dominated by dog hunting issues. Instead, crabbers from the coast and concerned fishermen from the Lake Guntersville area took center stage. I’ll let Chris Blankenship and the Marine Resources Division deal with the crabbers, and I’ll discuss the Lake Guntersville fishery. Apparently, several groups are concerned that the lake is on the decline and steps like supplemental stocking, reductions in creel limit, and other items should be addressed to save the lake. I’ve asked my fisheries staff to examine the fishery at Guntersville and prepare a statement addressing the concerns. The following was written by Damon Abernethy, assistant chief of Fisheries.

 

A Little Bass Biology …

A bass’s total length at age 3 is a good indicator of growth potential. Largemouth bass in most Alabama reservoirs attain lengths of 12-14 inches by this age. Growth rates of Guntersville’s largemouth bass are exceptional, reaching a mean total length of 15.5 inches by age 3.

Recruitment is the abundance of fish surviving to reach 1 year of age. It can differ vastly from one year to the next depending on environmental and biological variables that can have a significant impact on recruitment potential. Despite the fact that Guntersville tends toward lower recruitment, environmental conditions in 2008 yielded an all-time-high young-of-year bass. Unfortunately, weak year-classes followed in 2010 and 2011 creating a noticeable void behind the 2008 year-class. Good year-classes were produced in 2012 and 2013 that have fully entered the fishery and will sustain it moving forward.

At approximately 40 percent, the annual mortality rate of Guntersville’s largemouth bass is considered moderate. However, to make fishery management decisions, fishing mortality must be separated from natural mortality because only the fishing component can be controlled through management regulations. At the present time, research indicates that combined fishing mortality (harvest, hooking and delayed tournament mortality) is approximately 10 percent, while natural mortality accounts for the other 30 percent.

 

Will Reducing the Creel Limit Help?

Recent creel surveys show Lake Guntersville is dominated by bass anglers who practice catch and release. Nearly 90 percent of the fishing effort was directed at bass. Bass tournaments are very popular on Lake Guntersville and almost universally self-impose a five-fish limit and require mandatory fish release. The Bass Angler Information Team Program has monitored and recorded the statistics from bass tournaments for the past 30 years and indicates Guntersville is currently producing a quality of fishing almost identical to the 30-year average for the lake.

Angling effort has been relatively constant over the period in question with no discernable changes in bass harvest rates. Recent creel surveys indicate only 5 percent of anglers harvested any bass. They also documented an average catch rate of 0.5 bass per hour, meaning less than half of Guntersville’s anglers catch five or more legal bass per day. Given these estimates, reducing the creel limit – even to five per day – would only change the behavior of about 2 percent of Guntersville’s anglers.

There are only four types of bass mortality occurring at Lake Guntersville: natural mortality, hooking mortality, delayed tournament mortality and consumptive harvest. Reducing the creel limit would impact only one of those four. The other three combined account for the demise of seven times more bass than does consumptive harvest.

Expectations that harvest restrictions will improve fishing are only realistic if the primary sources of mortality are limited, or curtailed, by the regulation. Clearly, this would not be the case. The recent decline in fishing quality must be attributed to something else that can be explained by examining the historical bass year-class production over time.

The most abundant year-class on record was the one produced in 2008, resulting in a number of fish 2.5 times greater than what is produced in a typical year. This phenomenon was documented to a lesser extent in many other Alabama reservoirs and was correlated with the severe drought of 2007-2008. Given the rapid growth-rates of Guntersville’s bass, the 2008 year-class began to reach legal size in 2011. Since then, catches have mirrored the evolution of this year-class over time. Record densities of 15- to 18-inch fish were documented during 2011 and 2012, and the abundance of bass over 20 inches began peaking in 2014. Given a reasonable life expectancy of about 10 years, most of these fish are now disappearing from the population. However, we expect to see some very large fish caught from the remnants of the 2008 year-class. Casey Martin’s 40 pounds 11 ounces limit caught in the Bass Fishing League tournament on March 4, 2017, is a testament to this.

 

The Flaw Behind Supplemental Stocking

Anglers often believe restocking is an easy way to boost the quality of fishing in reservoirs; however, the math simply doesn’t add up. Few anglers have a grasp on just how many juvenile bass are produced in a typical reservoir. Assuming a conservative estimate of 3,000 fingerlings per acre, a 70,000-acre reservoir such as Guntersville naturally produces 210 million fingerlings every year. The Alabama Wildlife & Freshwater Fisheries Division has three fish hatcheries capable of producing approximately 500,000 fingerlings, annually. If the Division’s entire production of largemouth bass fingerlings was stocked into Guntersville, it would increase total abundance by only 1 percent.

There has never been a documented spawning failure in any of Alabama’s reservoirs. Bass are prolific spawners producing a tremendous number of eggs. A single 3-pound largemouth bass can lay over 20,000 eggs every spring.

So why is it that a typical spring electrofishing sample on Guntersville yields less than 10 age 1 bass/hour? The answer is natural mortality. Angling pressure does not affect 2- to 5-inch bass. These fish are dying from natural causes such as predation, disease and competition among themselves and with other species. Stocked fish must survive the same environmental conditions as naturally spawned fish. Adding more fish will not address the factors that cause their mortality. The abundance of age 1 bass in a reservoir is determined solely by the environment in which they must live.

Previous reservoir stockings have been done with the goal of introducing certain desirable genetic traits such as those of Florida bass alleles. This was done successfully at Guntersville over 20 years ago, but is not feasible to do again. Stocking a large reservoir like Guntersville with the goal of increasing abundance would be futile and cost-prohibitive, and shift hatchery production away from areas where success is being realized.

 

As you can see from Abernathy’s data, Lake Guntersville is still an extremely productive fishery. It may be down a bit by Guntersville standards since the unusually high recruitment of 2008 first matured, but it’s still better than 90 percent of the fisheries in Alabama. Whether you are discussing deer, turkey or bass, wildlife populations experience fluctuations in numbers over time. That is why we must base our decisions on scientific data rather than emotions.

 

Chuck Sykes is director of the Alabama Division of Wildlife and Freshwater Fisheries.