Understanding Aeration for Marine Livewells & Baitwells

Better Fishing Results & Healthier Fish:
The New Benchmark In Livewell Performance

As we strive to improve customer’s experience with our livewell products we have been gathering research on fish health as it relates to tournament and catch and release fishing.

Comparing the data to the performance of current “best-in-class” aerators on the market, a significant opportunity for improvement was identified.

As you will see in the following report, fish in a livewell environment are stressed and have definable oxygen requirements necessary to stabilize, be returned to their natural environment, to grow bigger, and to live and fight again!

Importantly, this data has enabled Flow-Rite to categorize the performance of our current aerators, which already set industry standards for oxygenation, and develop a premier addition to our aerator product suite that is economical and establishes the benchmark for livewell aeration performance.

Understanding O2 Solubility Science:
The common currency of all aeration systems

Air is about 21% Oxygen 78% Nitrogen and the rest various stuff that fish really don’t care about.
Water solubility of pure oxygen at 25°C and pressure = 1 bar is ~ 40 mg/L water. In air with a normal composition the oxygen partial pressure is 0.2 atm. This results in dissolution of 40 x 0.21 ≈ 8.4 mg O2/L in water that comes in contact with air.
Oxygen solubility is strongly temperature dependent and decreases at higher temperatures. Oxygen solubility is negatively correlated with the amount of dissolved solids.
Consequently, oxygen solubility in freshwater exceeds that in seawater by 1-3 mg/L, depending on temperature.
Bottom line – in freshwater, we can achieve a baseline of ~8.4 mg/l oxygen at 25°C in water. This is our maximum replenishment goal to keep fish healthy.

Air Derived Saturation in mg/l (ppm)

In Summary: Air = ~21% Oxygen
Air derived saturation = ~8.4 mg/l Oxygen @25°C

Understanding Fish O₂ Consumption Science:
Oxygen use in Livewells & Baitwells

Various studies dating back to the 1970’s and earlier have investigated the amount of oxygen used by aquatic animals. The amount of oxygen consumed by these aquatic animals varies with species, size, temperature, time since feeding, degree of physical activity and other factors. One recent study from Auburn University’s Department of Fisheries and Allied Aquacultures determined the average oxygen consumption rates for adult fish usually are between 200 and 500 mg oxygen/kg fish/hour.

Auburn University goes on to additional oxygen use assumptions and results. They make comparison with game fish vs. bait fish. Large 500-gram channel catfish were reported to use 480 mg oxygen/kg fish/hour. In contrast, 10-gram channel “bait” catfish consume 1,050 mg oxygen/kg fish/hour.

Oxygen consumption is also strongly dependent upon temperature – the rate roughly doubles with a 10 degrees-C increase in temperature within the temperature tolerance of the species (confirmed by Schramm & Heidinger 1988). Although less data are available on oxygen consumption by crustaceans, it appears that shrimp consume oxygen at rates similar to those of fish.

Here is what the summary of biology & goal for success looks like:
500 mg O₂/kg fish per hour for calm fish & 1000 mg O₂/kg fish per hour for stressed fish as a benchmark for assessment

Results from recent fisheries research publications:

Aquatic species research has further refined oxygen consumption rates needed to maintain healthy Livewell and baitwell environments. Here we’ll explore more of that information.

Fish O₂ Consumption:
Recommended O₂ range in Livewells:

Recent Texas Parks and Wildlife (TPWD) studies and corresponding recommended
dissolved oxygen levels can be summarized thusly:

The most important factor relative to minimizing stress and mortality on livewell held
bass is dissolved oxygen. Warmer water naturally holds less oxygen than
cooler water. At a moderate water temperature of 70˚F (21°C), 100% air derived
oxygen saturation is 8.9 mg/L (ppm). Saturation rates drop at higher temperatures
of 80 (26.6) and 90˚F (32.2°C), to 8.0 and 7.3 mg/L.
Oxygen levels less than 5.0 mg/L are harmful to bass, especially if allowed to
remain this low over extended periods.
TPWD defines sufficient dissolved oxygen levels to be 7.0 mg/L or greater.
Therefore, the attainable and acceptable range of air supplied dissolved oxygen is
between 8.4 and 5 mg/l at 25°C (standard pressure and temperature) [see graph].

Air derived saturation = ~8.4 mg/l Oxygen @25°C

In Summary:
Minimum Allowable = 5mg/L O₂ @ 25°C

The Maths of Livewells: Fish Consumption of O₂ within a Livewell

30 gallon live well = 113.5 liters

9.25 mg/liter O₂ @ 20°C (1 atm – solubility) [Chemistry]

Minimum allowable O₂ level = 5 mg/liter [TPWD]

Available O₂: (9.25 – 5) x 113.5 = 482.4 mg

6 (21-inch bass) * 6 lbs = 16.33 kg / bass

O₂ consumption 500 mg/kg fish – hour [Biology]

Why that's so important:
6 ave. bass have ~3.5 minutes of oxygen w/out replenishment before dropping below 5 mg/L O₂ (in a 30 gallon livewell).

This leaves 3.5 minutes before a dangerous situation is presented to the six, captive fish!

New Marine Product Coming Soon!

Based on the information and research in these articles, Flow-Rite has developed our best performing Livewell Aerator yet!
Follow Us On Social Media to catch our product launch coming soon this Spring 2025!

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