Striped Bass - Dissolved Oxygen


Hypoxia can occurs when dissolved oxygen levels dip below 3 to 4 ppm in water.

The Striped Bass needs Dissolved Oxygen levels over 5 parts per million (ppm).
Their Oxygen Preference is between 8.1 - 10.1 (PPM) with the peak activity around 9 (PPM).
Temperature preference between 50 and 75 degrees.

Dissolved Oxygen (DO) refers to the level of free, non-compound oxygen present in water or other liquids.
It is an important parameter in assessing water quality because of its influence on the organisms living within a body of water.
In limnology (the study of lakes), dissolved oxygen is an essential factor second only to water itself.

Temperature limits the amount of oxygen water can hold.
So in general, summertime Lake Ouachita water hold less oxygen than can winter waters.
During hot weather the water becomes stratified, or divided into several layers, with the upper layer being the warmest and highest in oxygen.
The largest impact on striped bass often occurs in late summer (August and September) when water temperatures are highest and DO values are lowest.
Deeper levels are cooler but contain less dissolved oxygen.
This will generally occurs during the latter part of the summer and varies in magnitude from year to year.
As summer progresses, the upper layer becomes too warm for stripers, which prefer water less than 78 degrees, and the fish move to deeper and cooler waters where the best balance of cool temperatures and high levels of oxygen are found.

As the Dissolved oxygen levels in the lower layers are depleted to around 3 ppm, the suitable habitat for the striped bass is reduced, they become stressed will sometimes quit feeding and maybe die.

Stripers caught during this time of the year should not be released.

As the summer sun continues to warm the lake, the surface temperature increases between the surface (epilimnion) and deeper waters (hypolimnion). The temperature differences eventually create a physical called stratification (the formation of layers), water temperatures decrease from the surface to the bottom
The lake now stratifies into three layers of water a situation termed summer stratification.
The upper layer is a warm (lighter), well-mixed zone called the epilimnion.
Below this is a transitional zone where temperatures rapidly change called the metalimnion.
The layer of rapid temperature change separating the two layers is called the thermocline.

The lake's temperature variations are important in influencing what types and how many fish will live and reproduce in the lake.

IF the colder, deeper waters of the hypolimnion have enough oxygen, then that area will provide a refuge for fish species that prefer, or require, cooler water temperatures.
However, if dissolved oxygen levels become too low in the cooler hypolimnion zone and fish are forced into the warmer surface waters, Stipers may not be able to survive.
Water temperature is one of the most significant factors to rely on when trying to locate and catch Striped Bass.
As water temperature changes throughout the year, so does fish behavior and metabolism.
Learning to identify how Ouachita changes and how stripers adapt to these changes can improve your success.

Fishing for Striped Bass during the end of the summer months is often frustrating because warm water temperatures can make finding and catching fish difficult. And sometimes when you do find them they won't eat.

 In early fall a precursor to the fall turnover is when upper water temperature drops into the 75° F range.

Pre-turnover water temperatures instinctively cue fish that winter is coming and feeding activity increases

What is fall turnover?

It’s a process that breaks down the stratification, or layering, of warm surface waters above cool or cold deeper waters that occurs in lakes during the summer.
During the summer, mixing only occurs in the uppermost layer of water.
Fall turnover occurs as surface waters cool, become more dense than underlying layers, and sink, thereby pushing the underlying water layers to the surface.
This mixing action occurs until all water is the same temperature from surface to bottom.
Dead zones and DO levels can vary widely from year to year, and habitat preferences of stripers depend on more than just DO levels.

The USGS Water Science School
Dissolved Oxygen
Nathan G. Smith, Texas Parks and Wildlife Department:
Adult striped bass are vulnerable to high summer water temperatures and low dissolved oxygen (DO) in southern reservoirs, potentially resulting in poor body condition and elevated mortality.


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