Jeff, Good work, now you know more about the reality of aerated livewell water in the summer and the need for supplemental compressed oxygen. Your DO meter speaks the truth and the truth about livewell water quality can be ugly when you test the DO Saturations, especially in aerated bass boat livewells in the summer.
The short answer is maintain the DO Saturation at 100% or greater during total time of transport (1 fish , 10 fish or 100 fish), “too much oxygen” is not an issue for 7-8 hour transport in bass boat livewells or weigh-in bags, too much air causes nitrogen supersaturation (i.e. air venture entraining air on livewell water pump) can cause problems ( pop-eye, tissue emphysema, air embolism, bends, etc.).
Looking forward to seeing your DO Saturation test of the bass boat livewells when they arrive at the weigh-in containing limits of fish… if the officials will allow you to test the boat livewell water containing fish. That may be a problem, but I hope not.
Beware of the oxygen and air gas bubbles… read on.
TOXIC OXYGEN BUBBLES
Toxic Oxygen Bubbles – Thousands of Micro-Fine Oxygen Bubbles that remain suspended in water columns in livewells and bait tanks can poison live bait and tournament fish in livewells and bait tanks. These tiny micro-bubbles are so small and light that they cannot escape the water surface and remain suspended in the water column,
A LESSON IN OXYGEN BUBBLE SIZE IN SPORTSMEN’S LIVEWELLS AND BAIT TANKS
1. Water and gas chemistry – micro-fine oxygen bubbles so tiny they remain suspended in the water column that make livewell water look milky transfer oxygen into solution fast and efficiently, quickly saturating/supersaturating water in seconds in a typical 20-30 gallon livewell or bait tank. Diffusers that make larger bubbles may take an extra minute or two to achieve the same DO saturation/supersaturation, but the final result is the same DO Saturation.
2. Fish Physiology and Fish Pathology – another matter that is seldom mentioned is that micro-fine oxygen bubbles negatively affect fish health – oxygen poisoning caused by continuous exposure to micro fine oxygen bubbles that coalesce to fish gills, cornea’s, scales, skin and fins can cause serious chemical burns and tissue damage resulting in blindness, death or disabling scar tissue if the fish survives the initial insult. Oxygen toxicity is usually caused by the fisherman’s ignorance of the device that makes the oxygen bubbles in his livewell water.
Micro-pore oxygen diffusers and livewell water pumps that entrain oxygen or air on the inlet side of a water pump’s impellers gas venturi device can produce thousands of suspended micro-fine gas bubbles in the livewell water column as the oxygen goes through the pump’s impellers. The size of an oxygen or air bubble can dramatically affect livewell water chemistry, gas transfer rates and dissolved gas concentrations.
We queried university professors and experts. Our concern is the pathophysiology (oxygen toxicity) occurring when micro-fine oxygen bubbles stick inside fish gills, get into blood, stick in eyes, on scales, fins and skin.
We asked University Professors, Fish Physiologist, the real fish doctors:
When captive fish are forced to breathe in clouds of suspended micro-fine oxygen bubbles (so fine the water looks milky) in livewells with relatively small functional water volumes, can these tiny gas bubbles injure fish or bait?
Is the stress response increased? Is the probability of delayed mortality increased?
Are we actually causing physiologic harm to tournament fish or live bait when holding and transporting them in clouds of bubbles for hours or even all day?
When we transport tournament bass, redfish, snook or live bait for hours or all day, what happens to gill tissue when thousands of tiny oxygen bubbles remain stuck in gills, on scales and fins all day?
We thank these university professors for offering their time, providing their knowledge, expertise and opinions freely so that catch and release tournament anglers, as well as fishermen worldwide, can become better educated and hopefully take better care of live tournament fish and live bait in livewells and bait tanks during live transports.
We appreciate these expert opinions in fish cardiovascular physiology, fish biochemistry, fish pathology, fish physiology, and the principles and practices of modern aquaculture techniques.
EXPERT OPINION
Toxic Oxygen Bubbles – Thousands of Micro-Fine Oxygen Bubbles in Livewells can poison live bait and tournament fish.
Micro-pore oxygen diffusers and some bait pumps that entrain oxygen or air on the inlet side of a water pump’s impellers can produce thousands of suspended micro-fine gas bubbles in a livewell water column. The size of an oxygen or air bubble can dramatically affect livewell water chemistry, gas transfer rates and dissolved gas concentrations.
We queried university professors and experts. Our concern is the pathophysiology (oxygen toxicity) occurring when micro-fine pure oxygen bubbles physically stick inside fish gills, get into blood, stick in eyes, on scales, fins and skin.
We asked the real FISH DOCTORS, the FISH PHYSIOLOGIST, the UNIVERSITY PROFESSORS
When captive fish are forced to breathe in clouds of suspended micro-fine oxygen bubbles so fine the water looks milky, in livewells with relatively small functional water volumes, can these tiny gas bubbles injure fish or bait?
Is the stress response increased?
Is the probability of delayed mortality increased? And, are we actually causing physiologic harm to tournament fish or live bait when holding and transporting them in clouds of bubbles for hours or even all day?
When we transport tournament bass, redfish, snook or live bait for hours or all day, what happens to gill tissue when thousands of tiny oxygen bubbles remain stuck in gills, on scales and fins all day?
We thank these university professors for offering their time, knowledge, expertise and opinions freely so that catch and release tournament anglers, as well as fishermen worldwide, can take better care of live tournament fish and live bait in livewells and bait tanks during transport. We appreciate their expert opinions in fish cardiovascular physiology, fish biochemistry, fish pathology, fish physiology, and the principles and practices of modern aquaculture techniques.
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Professor Joseph J. Cech, Ph.D.
University of California – Davis Campus
Department of Wildlife, Fish, and Conservation Biology
1393 Academic Surge
Davis, CA 95616-8751
(530) 752-3103
[email protected]
Specialty: Physiological adaptations and adjustments of fish to their environments
“Micro-fine gas bubbles sticking to gills could obstruct respiratory gas exchange, by blocking ventilatory water flow between the minute lamellae on the gill filament surfaces.
If the livewell transport water becomes clouded, appearing milky with miniscule bubbles that adhere on gills and scales or to the inside walls of your livewell, consider these conditions potentially toxic and generally unhealthy for the exposed fish.
If the gas/gill exposure is persistent and the partial pressure of the oxygen remains near 1 atmosphere (instead of 0.2 atmospheres, as in air), the exposed fish’s chances of survival will probably decrease.
Compressed oxygen is a good thing when supplied continuously within safe dissolved oxygen concentrations, but exposure to compressed oxygen or delivered at high partial pressures can physically harm your fish. With extremely high oxygen partial pressure in the water, the fish may stop breathing, allowing carbon dioxide to build up in the fish. This may lead to acid-base changes (respiratory acidosis) in the fish and increase delayed mortality after release.
It is important to remember that pure compressed oxygen contains five times the oxygen content as air does. Thus, proportionately less (about 1/5 less) gas flows (bubbling rates) are needed from a pure oxygen supply, compared with an air supply, to adequately oxygenate water for fish.
Very small (micro-size) oxygen bubbles should dissolve faster than larger bubbles because of their greater surface to volume ratio, but all gas bubbles (air or oxygen) need some ‘solubility space’. Without sufficient ‘space’ available for the bubbles to dissolve, tiny micro-fine bubbles may remain suspended within the water column, attach to surfaces, or slowly, rise to the surface. Of course, fish do not breathe (gaseous) oxygen or air bubbles, the oxygen must first be dissolved in water for it to diffuse across their lamellar membranes.
And also, saltwater has a higher density than freshwater does. The higher water density compresses gas bubbles to a smaller size. This characteristic, along with saltwater’s lower gas solubility demands that saltwater livewells should be monitored for signs of oxygen/air bubble-related problems at least as well as freshwater ones.”
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Professor Bruce Sidell, Ph.D.
University of Maine
School of Marine Sciences
306 Murry Hall
Orono, Maine 04469
Specialty: Cardiovascular physiology and biochemistry of fish
“If you observe clouds of suspended micro-fine oxygen or even air bubbles in fish transport water, you may be using too much of a good thing. Micro-pore diffusers can generate masses of tiny oxygen bubbles.
This condition may excessively supersaturate the water with oxygen if the mass of gas bubbles cloud the water and remain suspended; and, extreme hyperbaric oxygen can be toxic because of free-radical generation.
Clouds of micro-fine air bubbles may also cause problems with nitrogen toxicities, the bends and air emboli. Tiny gas bubbles may affect water quality positively or negatively, either way, avoid transport conditions where clouds of gas bubbles remain in suspension.
There exists a rather rich and extensive literature on oxygen toxicity and gas bubble trauma. Plus, the adherence of the small bubbles to gill surfaces could exacerbate this problem further.
My guess is that the potential oxygen toxicity from adherence of the pure O2 bubbles to the surfaces of delicate epithelia is potentially more of a problem than the possibility of “drying out” the surfaces as you speculate. Both must be considered.
These bubbles, after all, are in equilibrium with the water in which the fish swim, a far better source of water than the semi-permeable surfaces of the fish itself.
Arterial gas embolism and tissue emphysema can be a real and present danger when transporting live fish, avoid clouds of suspended gas bubbles in hauling water at all cost.
In my experience of transporting large numbers of capture-stressed fish (although in my case they were striped bass or salmonids that were captured by nets, not tournament hooked fish that were fought and landed), two key ingredients promote well-being of these animals.
1. Elevating the partial pressure of O2 above saturation with compressed oxygen and deliver bubbles large enough to escape the surface. A very gentle bubbling with pure O2 is sufficient for preventing coalescence. Problems may arise if gas bubbles stick to gill tissue and remember, with pure oxygen, you need only 1/5 the volume compared to the volume of air needed. Air is composed mostly of nitrogen, micro-fine N2 bubbles can stick to gills too, causing another related set of problems with additional stressors. Any gas bubbles attaching to gills can impair respiration degrading fish health; when transporting fish in foamy water with thousands of suspended bubbles, consider the probability of hypoxia, hypercarbia, respiratory acidosis, disease and possibly death.
2. Elevate the salinity of the water to 3-5 ppt. Something like Instant Ocean or seawater is great, but even just NaCl without iodine would do. Salt will still be very helpful when transporting freshwater fish. Remember that these animals regulate their internal ionic and osmotic composition at much higher levels than freshwater (generally 300-340 mOsm). When under stress, they lose ions and this becomes even more stressful. On top of that, the energetic demand of ion pumping can represent a significant energy expenditure requiring even more oxygen. I am confident that the elevated salinity will help.
Saltwater is denser that freshwater, therefore, micro gas bubbles will be compressed even smaller maximizing coalescence. In other words, this problem is multiplied in saltwater. Stress is multiplied too.”
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Professor Kevin M. Fitzsimmons, Ph.D.
University of Arizona
Environmental Research Lab
Tucson, AZ 85712
Phone (520) 626-3324
[email protected]
Specialty: Aquaculture Research Scientist
“Micro-fine gas bubbles that remain suspended in the water column increase the dissolved gas concentration in water more efficiently than larger bubbles in livewell water. Space must be available in the livewell for bubbles to dissolve. Most fish can’t breathe gaseous bubbles made with air or oxygen.
Gas bubble size directly affects water chemistry and when highly concentrated, can negatively affect fish health. Micro-fine gas bubbles may be unhealthy for captive fish being transported in boat livewells and ice chest having relatively small water capacities. Larger gas bubbles may be safer and healthier for captive fish than excessive micro-fine bubble environments.
Water Chemistry and micro-fine gas bubbles.
Micro-fine gas bubbles that remain suspended in the water column dissolve quicker and force more gas into solution than larger gas bubbles, a plus for water chemistry when the goal is high dissolved gas concentrations.
Fish Health and micro-fine gas bubbles
Transporting live fish in livewell environments containing clouds of micro-fine gas bubbles with excessive gas supersaturation can be dangerous when transporting live fish, increasing chances of delayed release mortality.
Fish transported in milky looking livewell water containing clouds of suspended tiny micro-fine bubbles can increase stress, cause physical injury, increase susceptibility to infection and disease and may ultimately increase post release delayed mortality.
Micro-fine gas bubbles can stick to gill filaments, scales, fins, skin, and eyes, cause gas bubble trauma and gas embolus. Gill damage and gas embolisms negatively affect fish health and survival, compromise respiratory gas exchange and lead to hypoxia, carbon dioxide retention and respiratory acidosis.
Micro-fine bubbles consisting of pure oxygen can attach to gill filaments, drying, irritating, oxidizing and actually causing chemical burns to delicate epithelial tissue. Pure oxygen gas is a potent oxidizer.
Micro-fine air bubbles consisting primarily of nitrogen can cause gas bubble disease and tissue emphysema in captive fish being transported, a medical condition similar to the bends affecting SCUBA divers.”
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Professor Claude E. Boyd, Ph.D.
Auburn University
Department of Fisheries and Allied Aquaculture
Auburn, AL 36849
(334) 844-4078
[email protected]
Specialty: Water Quality and Aeration Systems
“Transporting live fish in livewell environments containing clouds of micro-fine gas bubbles is not healthy for most fish. Continuous exposure to tiny gas bubbles that attach to gill filaments is not normal and unhealthy. Additional transport stress must be avoided as much as possible.
Micro-fine gas bubbles that coalesce and stick to fish’s gills are not healthy and may physically disrupt normal respiratory gas exchange. A few fish specie do breathe gas, but respiration for most fish specie, available gaseous oxygen must be in solution or dissolved in water, commonly known as dissolved oxygen (DO).
When clouds of gas bubbles are visualized in livewell water and the bubbles are suspended within the water column, oxygen bubbles generated with pure compressed oxygen or liquid oxygen can burn gill epithelial cells located within gill filaments. Pure oxygen increases speeds at which oxidative reactions occur. Exposure time and oxygen partial pressures govern oxidative reactions.
Oxidative damage induced by pure gas exposure can harm fish. Upon releasing fish after the transport, provided the fish survives the initial toxic insult with oxygen; gill scar tissue may develop rendering highly stressed fish even more susceptible to pathogens resulting in additional delayed mortality rates occurring within days or even weeks after release.
Clouds of tiny air bubbles trapped and suspended within the water column may create additional fish health problems during transport. Also, the potential for gas bubble disease and arterial air emboli must be considered. Fish transported in shallow livewells cannot dive deeper increasing water pressures that will dissolve fine bubbles trapped within the circulatory system like wild fish released in lakes and swimming to deeper depths.
Excessive aeration with air can harm captive fish being transported in closed livewell systems having limited water volumes. Air entrained on the inlet side of livewell water pump indicates a defective pump and a common cause for high dissolved nitrogen supersaturation. This sort of pump defect may develop dangerously high dissolved nitrogen concentrations when air is sucked into the pump inlet and then pressurized by the pumps’ impellers.
Prolonged exposures to excessive nitrogen supersaturations can cause the bends, create additional stress and gas emboli. The bends, when caused by a defective water pump, is a mechanical problem that is preventable. Understanding what problems to look for and where to look is essential. If you detect an air leak on the inlet side of your livewell pump, repair the air leak.”
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SUMMARY
You now should be able to better judge and evaluate various livewell oxygenation technologies from a fish health point of view. The health of tournament catch and release fish is dependent upon your understanding of the oxygen technology you choose to use in your livewell. Choosing the wrong livewell oxygen equipment can increase stress during transport and ultimately cause disease and increase delayed mortality. Choosing the right livewell oxygen technology can greatly improve summer livewell water quality improving survival up to 93% in the harshest summer tournament conditions.
