When Does It Work?
Sport fish stocking is an important management tool for biologists in their efforts to improve sport fisheries or to recover species in peril. Unfortunately, the use and expectations for success from fish stockings is often misunderstood by the general public.
As a general rule, if a particular species, such as largemouth bass, occupies a body of water and natural reproduction is occurring, then the stocking of additional fish will not increase the number of bass available to anglers. This management concept is hard for many to accept. However, the explanation is not overly complicated. A fish population in a body of water occupies that body of water at an abundance that is determined by the other species that are present, the available habitat, water quality, nutrients, water temperature range, food, and mortality rate. All of these factors result in a body of water supporting a maximum weight or biomass of all fish present. Biologists refer to this as “carrying capacity”. Each species of fish in a particular body of water also has a maximum weight, which is a portion of the overall “carrying capacity”. Under these circumstances, stocking fish will not result in more adult fish unless the species of interest is not reaching its full carrying capacity for some reason.
Therefore, Alabama fisheries biologists take advantage of stocking to improve fish populations under two general circumstances; (1) stocking fish that are not able to reproduce or have limited reproduction in the wild and (2) stocking fish with desirable genetic characteristics.
Striped bass is an example of a native Alabama species that has lost its ability to reproduce in the wild and must be maintained by stocking.
Due primarily to the construction of dams on most Alabama rivers, striped bass no longer have access to the long stretches of free-flowing river they need to successfully spawn and for their eggs to hatch. Therefore, annual stockings of 1 to 6 fingerlings per surface acre have proven successful in establishing and maintaining fisheries for this species. Without these stockings, striped bass would disappear from most of Alabama’s major reservoirs.
The introduction of desirable genetic characteristics is the reason Florida largemouth bass are stocked in many Alabama reservoirs. Largemouth bass have two sub-species, with somewhat different characteristics. Florida largemouth bass are native to Florida and Northern largemouth bass are native to the rest of the range, including Alabama. Florida largemouth bass grow to a larger size but are not as aggressive as Northern largemouth bass and are therefore harder to catch. Young Florida largemouth bass that are stocked into Alabama waters will displace some of the young Northern largemouth bass so the overall population is not increased. However, when the Florida and Northern bass reach adult size, they can interbreed, resulting in an overall bass population with the better growth of Florida largemouth bass, while retaining the more aggressive nature of the Northern largemouth bass.
Alabama fisheries biologists are using hatchery raised fish to enhance or develop great fishing opportunities. Information about the Alabama waters that have been stocked in recent years can be found at www.outdooralabama.com/research-mgmt/hatcheries.
The following is a description of many of Alabama’s Division of Wildlife and Freshwater Fisheries (ADWFF) recent public water fish stocking efforts.
Florida Largemouth Bass
The intent of Alabama’s largemouth bass genetic enhancement program is to introduce the superior growth characteristics of the Florida sub-species not to increase abundance.
In order to maximize the effectiveness of the Florida largemouth bass genetic enhancement program, reservoirs that were thought to provide the best possible habitat for Florida largemouth bass were selected for intensive stockings, with the stockings of fingerlings being concentrated into isolated areas of each reservoir. Lake Guntersville was stocked with Florida largemouth bass using this intensive strategy for three consecutive years from 1992–1994. Subsequent genetic assessments revealed that this new strategy was a great success and similar efforts were duplicated at reservoirs throughout the state. Although success rates varied, populations in Guntersville, Lay, and Wheeler have all experienced significant positive shifts in the frequency of Florida genes. In recent years, ADWFF dedicated more pond space on its fish hatcheries to the production of Florida largemouth bass fingerlings and can now produce up to 500,000 annually. Division biologists have continued to follow this same intensive approach to Florida largemouth bass stocking and recently began a 3 year stocking cycle in an area of Sandy Creek on Lake Martin. This cycle will introduce up to 1.5 million Florida largemouth bass fingerlings into a concentrated area where they will have the best opportunity to supplant the native fingerlings.
Results from crappie stockings have been extremely variable. Presently it remains unclear if these experimental stockings will contribute to the fishery and dampen the “boom and bust” cycles that this species is known for.
Young crappie are more sensitive to environmental change than many other species. This causes highly variable recruitment, in which many young crappie survive in some years and very few survive in other years.
When the fish reach adult size, the result can be a “boom and bust” fishery. To address this problem, ADWFF has stocked several public reservoirs with black crappie over the last 10 years. Yearly crappie stockings have ranged from 40,000 to 120,000 fish in Weiss Lake. Other reservoirs such as Lewis Smith, Logan Martin, Inland Lake, and Mitchell Lake have also received crappie stockings in recent years. Most of these stocked crappie are marked so that they can be differentiated from the native fish when ADWFF biologists sample the populations. Continued stocking and evaluation will be required to determine if stockings are successful.
Due to the widespread construction of dams on Alabama’s major rivers, striped bass are no longer able to successfully reproduce and maintain their populations in many of our rivers and reservoirs. In 1987 the fish and wildlife agencies of Alabama, Florida and Georgia along with the U. S. Fish and Wildlife Service formed a cooperative partnership with the goal to conserve and restore native Gulf striped bass. Since entering that partnership, the ADWFF has shifted its fish hatchery effort to the production of only striped bass fingerlings of Gulf strain stocks.
Presently the Alabama reservoirs and rivers that are annually stocked with striped bass are limited to those waters with suitable prey populations and habitats that reliably support striped bass populations adequate to provide a recreational fishery and where no significant natural reproduction is evident. ADWFF annually stocks 14–16 of Alabama’s reservoirs with approximately 500,000 striped bass fingerlings at a rate of 2–3 fingerlings per surface acre. These fish are produced at the three fish hatcheries operated by ADWFF and are stocked in the reservoirs each year during the months of May and June.
Hybrid Striped Bass
Hybrid striped bass have the warm water tolerance of white bass; therefore, it is possible to establish a fishery for hybrids in reservoirs and rivers that lack the cool water summer refuges necessary to support adult striped bass. Hybrids produced by Alabama fish hatcheries are crosses between striped bass females and the white bass males. They are fast growing and often reach weights of five to seven pounds within just a few years, offering anglers another species of fish to pursue in open water habitats.
Since hybrids are functionally sterile and relatively short lived, the populations can be managed simply by modifying the annual stocking rates.
This combination of good growth and warm water tolerance makes them particularly attractive for stockings in smaller lakes and reservoirs. At the present time ADWFF annually stocks 10–12 of Alabama’s reservoirs and lakes with approximately 300,000 hybrid striped bass fingerlings at a rate of 2–10 fingerlings per surface acre.
Channel catfish, when stocked in proper numbers, are a good compliment to largemouth bass/bluegill populations in small impoundments. The ADWFF State Lakes Program manages 23 public fishing lakes that range in size from 23 to 184 acres. Channel catfish provide an additional fish for anglers, are easy to catch, grow to large sizes and, perhaps most importantly, are good table fare. Consequently, they have become an angler favorite in State Lakes. Approximately, 120,000 channel catfish are stocked each year into State Lakes and other public bodies of water.
In order to maintain and improve the smallmouth bass fisheries in the tributaries of the Tennessee River in North Alabama, stocking emphasis is focused on those tributaries that enter from the south, draining Little Mountain and Moulton Valley in the central and western regions and Sand Mountain and the Cumberland Plateau in the east. Smallmouth bass populations are common throughout their native range of the Tennessee River drainage but appear fragmented due to reservoir construction and poor water quality. To date, 52,884 smallmouth bass fingerlings have been stocked in tributary streams of the Tennessee River.
Delta Largemouth Bass
Delta largemouth bass were stocked in two delta sites at 20–23 bass per acre during February 2010. Largemouth bass samples have been collected three times since then and recapture rates of tagged bass varied from 2% to 33% of the given size group of bass evaluated. Further study over the next 3 years will help biologists evaluate the stocking of this advanced size, fingerling bass while measuring their growth and survival success in the Mobile-Tensaw Delta.
Despite the Mobile Delta’s popularity for bass fishing, angler catch data derived from Alabama’s Bass Angler Information Team (B.A.I.T.) program reveal that from 1986 to 2009, only 62 bass larger than 5 pounds were recorded during 107,836 tournament angler hours. In fact, the Mobile-Tensaw Delta generally ranks among the lowest for both average size and catch rates of big bass compared to other public reservoirs throughout the state. The issue of low abundance of large bass is not caused by over-harvest. It is associated with a “grow fast – die young” quality. Delta bass fingerlings from larger-than-average size (most are 3 to 9 pounds) parent bass are raised at Marion Fish Hatchery. These fast-growing fingerlings generally reach the preferred stocking size of 6 inches (size varies from 5 to 10 inches) in February, are then tagged and released. Since each fingerling bass is individually tagged, follow-up surveys allow ADWFF biologists to evaluate growth and survival of stocked versus wild fish. Additional benefits to these stockings follows that, when these larger fingerling bass are stocked into a body of water, they should attain higher growth, survival, and reproductive success compared to their smaller wild counterparts. Given the potential for survival advantage over smaller wild fish, these larger stocked bass with selective growth characteristics should exert a positive genetic influence on the bass population, thus improving average size over several years.
Currently, 8 to 14 inch rainbow trout are stocked into the Sipsey Fork River below Lewis Smith Dam monthly, except August. Through a cooperative agreement between ADWFF and the U.S. Fish and Wildlife Service, biologists from Dale Hollow National Fish Hatchery in Tennessee stock about 25,000 fish annually. An additional 15,000 rainbow trout are being stocked annually by ADWFF as a result of a new relicensing agreement for the Alabama Power Company hydroelectric facility at Lewis Smith Dam. The Sipsey Fork is a “put and take” rainbow trout fishery sustained by stocking adult fish into this highly regulated stream. The cool water discharged from Smith Dam allows these fish to survive throughout the year.
Over the past 3 years, State hatcheries have stocked over 2,600 alligator gar into their native waters. Alligator gar is a predator high in the food chain, capable of consuming abundant non-game forage species too large for most other predators to eat. These fish are valued by anglers and bow anglers for their large size and fighting ability. The purpose of stocking alligator gar is to replenish a diminished population in the Mobile-Tensaw Delta system.
Alligator gar are a long lived species that can live up to 50 years. Continued management and stocking efforts will help restore these fish to historic population levels.
Approximately 6,500 southern walleye fingerlings were stocked into Lake Mitchell in 2006. They are native to the Mobile River Basin in Alabama and Mississippi but have experienced a significant decline in abundance due to habitat alteration in recent years. Southern walleye were once targeted during winter months by anglers, but few fish if any have been caught in recent times. ADWFF biologists attempt to collect adults in January and February each year for spawning purposes. Since few individuals are collected, few young are produced. Besides broodfish collection efforts through a cooperative agreement with the State of Mississippi and the U. S. Fish and Wildlife Service, southern walleye are being stocked in several small lakes to produce future broodstock. The recovery of southern walleye will be a long-term stocking project.
Marion Largemouth Bass, Bluegill and Redear Sunfish
Each year ADWFF raises “Marion strain” fingerlings, bluegill and redear sunfish based on requests from ADWFF biologists to stock small public impoundments.
The “Marion Strain” largemouth bass was developed at the Marion Fish Hatchery during the late 1960’s under the direction of Jack Snow. Selective traits from both the Florida and Northern sub-species of largemouth bass were combined to produce the “Marion Strain” largemouth bass. This genetically superior intergrade exhibited fast growth and excellent catchability, and readily adapted to its environment. This type of bass appears to be an excellent fish for small impoundments.
Bluegill and redear sunfish (shellcracker) are also raised for stocking small impoundments along with Marion bass. The classic bass/bluegill stocking ratio is used in lakes that has been newly built, renovated or drained. Biologists might also consider a supplemental stocking of bass or bluegill to enhance existing fisheries.
A unique use for redear sunfish occurred recently. They have been stocked to assist with the control of introduced apple snails, an invasive exotic species, in waters of Baldwin and Mobile counties. These snails can cause severe damage to native wildlife habitats. Redear sunfish are known for their ability to feed on young snails, thus the origin of the name shellcracker.
ADWFF stockings of Marion bass, bluegill and redear sunfish vary greatly each year but on average about 750,000 are stocked in Alabama’s public waters.