The striped bass, Morone saxatilis, is traditionally tied to coastal waters, yet it can definitively survive in non-marine environments. This species possesses a remarkable biological adaptability, allowing it to thrive in its native Atlantic Ocean and in numerous inland lakes and reservoirs across the United States. The ability of the striped bass to flourish in these freshwater systems is a testament to its unique physiological makeup, which manages the extreme shift in water chemistry.
The Biology of Salt Tolerance
The striped bass is naturally an anadromous species, spending its adult life in saltwater but migrating upstream to spawn in freshwater rivers. This migration requires the fish to be a euryhaline organism, capable of tolerating a wide range of salinities. The mechanism enabling this transition is called osmoregulation, primarily controlled by the kidneys and gills.
When in the ocean, the fish constantly loses water and gains salt. Specialized chloride cells in the gills excrete excess salt, while the kidneys produce concentrated urine to conserve water. Conversely, in freshwater, the body gains water and loses salt. The osmoregulatory system reverses, with gills actively absorbing salt and the kidneys excreting large volumes of dilute urine to eliminate surplus water, making permanent freshwater residency possible.
Establishment of Landlocked Populations
The existence of large, stable freshwater populations is largely a result of human intervention. Initial landlocked populations were often created accidentally, such as when dams built in the mid-20th century, like those on the Santee-Cooper River in South Carolina, trapped migratory fish in new reservoir systems. Seeing the success of these populations, fisheries management agencies began extensive stocking programs, introducing striped bass into hundreds of suitable inland lakes and reservoirs.
For landlocked populations to succeed, the environment must meet specific needs beyond the absence of salt. Striped bass require a large body of water that maintains a deep layer of cool, well-oxygenated water, often below 70 degrees Fahrenheit. In many reservoirs, warm surface temperatures combined with low dissolved oxygen levels can create a summertime “habitat squeeze,” limiting the area where the fish can comfortably survive and feed.
Reproduction and Growth in Freshwater
The most significant limitation is the striped bass’s precise reproductive requirement. Unlike many fish that spawn in still water, their eggs are semi-buoyant and must be kept continuously suspended in a flowing current for 30 to 72 hours until they hatch. If the eggs sink to the bottom, they will suffocate and die.
This need for a long stretch of river with a sufficient flow rate means that most landlocked populations in reservoirs cannot reproduce naturally. They must be maintained through annual stocking of hatchery-raised fingerlings. Only a few locations, such as Lake Texoma on the Red River and portions of the Coosa River system, possess the necessary riverine conditions to support a self-sustaining freshwater breeding population.
Landlocked striped bass exhibit excellent growth rates due to abundant prey like shad and herring. However, they typically do not attain the maximum size or lifespan of their marine counterparts. This is largely because the finite resources of a lake cannot support the massive biomass that the ocean sustains.