Research Spotlight

Summer Habitat, Exploitation, Connectedness, and Age Structure of Striped Bass in the Ochlockonee River Drainage, Florida

By: Stephen Stang, Andy Strickland, Ryan Henry, and Mike Allen

Before the construction of the Jackson Bluff Dam and formation of Lake Talquin in 1927, the Ochlockonee River supported a naturally reproducing population of Gulf Striped Bass Morone saxatilis, a genetically unique strain of Striped Bass that were historically found in coastal rivers from the Suwannee River, Florida to the Lake Pontchartrain Basin, Louisiana. The construction of dams eliminated access to critical spawning and thermal refuge areas throughout their historic range and populations began to decline. As a result, biologists from Florida, Georgia, Alabama, Louisiana, Mississippi, and the USFWS helped draft a Gulf Striped Bass Management Plan to outline goals for conservation and management of this popular gamefish throughout their native range. Annual stocking efforts are now necessary to sustain this species, and reliable sources of broodstock are important for hatchery operations.

Lake Talquin was eventually chosen as a broodfish repository for Gulf Striped Bass and has been supplying broodfish to both state and federal hatcheries for over 20 years. Male Striped Bass and Female White Bass M. chrysops are also collected from this system and spawned to produce all Hybrid Striped Bass M. chrysops x M. saxatilis used in Florida’s Sunshine Bass program. As a result of annual stocking efforts, a popular Striped Bass fishery exists in Lake Talquin and its tailrace for anglers looking to catch one of America’s premier gamefish.

In recent years, larger Striped Bass have become less common in annual broodstock collections (Figure 1). These larger fish (and presumably, older year classes) are not only popular among anglers, but Striped Bass that are age-3 and older are required by hatchery personnel for spawning purposes. Biologists speculated that the lack of large size classes was a result of high natural and/or fishing mortality. Striped Bass become more sensitive to warmer water temperatures as they age. Summer temperatures of thermal refuge areas in this system could be increasing due to climate change or habitat degradation and could be contributing to a high level of natural mortality of larger fish. Striped Bass are targeted heavily by anglers during the winter and spring months below Jackson Bluff Dam, and fish in Lake Talquin are targeted by anglers in a select few creek mouths during the summer months. Researchers aimed to understand how fishing mortality and habitat limitation due to a lack of thermal refuge are influencing mortality of Striped Bass in Lake Talquin and the Ochlockonee River.

Figure 1: Length-frequency of female Striped Bass collected from Lake Talquin and lower Ochlockonee River, Florida and sent to state and federal hatcheries for spawning from 1993 to 2022.

Biologists investigated the quality of summer habitat for adult Striped Bass throughout Lake Talquin during the summer of 2020. Hourly water temperatures were measured using HOBO temperature loggers, and dissolved oxygen levels were recorded weekly using handheld YSI units. Adult Striped Bass, especially fish greater than 4.5 kg, avoid water temperatures greater than 25°C and dissolved oxygen levels less than 2 mg/L. This fishery depends on the availability of thermal refugia. Electrofishing data and angler reports indicate that adult Striped Bass in Lake Talquin congregate in the mouths of creeks during the summer months as they provide a source of cool, oxygenated water. During wet summers, these creeks can flow up to a mile into the reservoir. In some of these creeks, a buildup of aquatic plants has resulted in reduced flow, increased temperatures, and sub-optimal dissolved oxygen levels. Temperature and dissolved oxygen data suggest that Lake Talquin currently offers marginal summertime habitat for adult Striped Bass. Several creeks where adult Striped Bass were historically sampled have become so impacted by the buildup of aquatic plants, muck, and reduced flows that they no longer provide summer habitat.

Biologists tagged 201 Striped Bass in Lake Talquin and the tailrace below the Jackson Bluff Dam from December of 2020 through February of 2021 (Figure 2). After a year, 80 of the fish were recaptured, with 47 harvested and 33 released. Annual exploitation was estimated to be 25%, with most of the effort focused directly below the Lake Talquin dam (8 recaptures in Lake Talquin and 72 recaptures in lower Ochlockonee) during the winter and spring on mainly 2 cohorts of fish (age-2 and age-3). Anglers harvested nearly 2/3’s of all fish caught over 24”. Dam escapement was evident, and 23 of the recaptured fish in the lower Ochlockonee were originally tagged in Lake Talquin. These data support a high level of connectivity between the population in Lake Talquin and the lower Ochlockonee River.

Figure 2: Tagging location for Striped Bass using Floy plastic-tipped dart tags.

An age sample was collected from Lake Talquin during the winter of 2021-2022. Fish from age-2 to age-4 were collected, while very few age-4s made up the sample (Figure 3). Stocking numbers (half as many fingerlings stocked in 2020 due to impacts of COVID) can explain the low number of age-2s observed. The low number of age-4s and lack of fish older than 4 is likely due to a high level of natural morality. Historically fish as old as age-6 were sampled in Lake Talquin.

Figure 3: Length-frequency and age distribution of Striped Bass collected from Lake Talquin during the winter of 2022 using gillnets (n=101) and hook and line (n=7).

Results from this study indicate that the lack of older age classes are likely due to a combination of degrading thermal refuge areas, angler exploitation, and dam escapement. These Striped Bass are living in the southernmost extent of their range; therefore, any change in climate has the potential to have negative impacts on this population’s persistence. There have been several management actions taken to conserve this population for future generations to enjoy. FWC biologists working with AHRES have undertaken shredding projects on several thermal refuge areas to restore critically important flows. A proposed regulation change will be presented to FWC’s commissioners in December to protect the limited number of adult cohorts below the Jackson Bluff Dam where exploitation appears to be highest. The proposed regulation would result in a 3 fish per person per day bag limit with only 1 fish greater than 24” per person per day, with the goal of reducing harvest of age-3 and older Striped Bass. A radio telemetry study to track movement of adult Striped Bass in Lake Talquin and the lower Ochlockonee River is also set to begin in 2023, with the goal of identifying thermal refuge areas that large fish are utilizing. This will allow biologist to fine-tune where habitat enhancement projects should be focused.  

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