Skittering and Snails Two ways Of Catching Or Avoiding low Oxygen in a pond

Tilapia in growing situations where the oxygen level is fluctuating  do not always have a way to communicate with humans to let them know that the oxygen level is dropping to a dangerously low level.  Except when they start skittering.  Skittering appears to be a process where the tilapia rise to the surface and suck a very thin layer of water from the surface thus drawing a more highly oxegenated or oxygen enriched layer of water from the surface.

The action of skittering by tilapia happens whenever the oxygen in the water is below the level where they can get it out of the water easily.  If the tilapia have just been fed the skittering may not signal a low oxygen level  because often, right after feeding, the tilapia will often come to the surface and skitter.  This skittering is not necessarily a sign of low oxygen , but generally means that there is not as much oxygen as the tilapia would like to have to digest the amount of food they have just eaten, so they are skittering for more..

Tilapia do generally go to the surface and draw the surface water down over their gills whenever they need to take advantage of a slightly greater amount of dissolved oxygen in the water drawn from the surface.  The level of oxygen can be 6ppm or above, and even though tilapia can get along fine at 6ppm, if they have just eaten a meal and have a full stomach and they need slightly more oxygen due to the need to digest the extra food in their stomach, they skitter.

This skittering helps to draw extra oxygen rich water (which is probably richer in oxygen than than the rest of the water below the surface where it is much lower) down over their gills thus giving themselves an advantage over fish and other creatures that can not  skitter.  This micron thick layer which is in direct contact with the oxygen rich atmosphere has enough dissolved oxygen in it for the tilapia to be able to meet its needs.  They may even be drawing tiny amounts of air or bubbles.

This skittering can also help the tilapia survive in situations where the oxygen is critaly low.  Hickling in his article told of a lake where tilapia were able to survive at virtualy  zero oxygen level for several weeks by skittering. TILAPIA HAVE LONG BEEN APPRECIATED for their ability to withstand low oxygen in ponds and lakes where almost every living animal in the body of water died, while the tilapia survived.  This shows that skittering can be comparatively be effective as long as their are not to many fish for them all to have a small area on the surface to skitter.

The process of skittering probably helps them when the oxygen is very low or at  zero parts per million.  Because the  oxygen rich microlayer of water on the surface of the body of water is pulled down from the surface over the gills where the haempglobin in the blood of the fish can extract the oxygen and allow the oxygen to be circulated to the parts of the body most requiring oxygen.

Several other things also seem to help.  One is that the tilapia is able to switch from
aerobic digestion to anerobic digestion thereby reducing the demand within the tilapia, and still another may be the tilapias ability to percieve the oxygen level and when it drops to one or two parts per million the fish seem to regurgicate the contents of their stomachs which  allows this food debris to drop to the bottom in a deep pond where its demand for oxygen is not translated to stress on the tilapia which are up twittering.

All of this tells what the tilapia do to respond to low levels of oxygen (which can be due to their own internal need after a heavy feeding.)
In any case none of us know a good way to measure this without an oxygen meter.

In this scenario there are large african Snails that may provide information (almost as good as an oxygen meter) as to the oxygen level in a pond.

They may be able to help because when we can pay attention to  what part of the pond they are in when it relates to oxygen. The snails can respond to the level of oxygen by  floatng to the top of the pond by creating gas inside of themselves or climbing up water plants in the pond.  So when almost all of the snails are out of the water or are floating at the surface, the ppm is generally below 3 ppm, which is dangerously low for most aquatic organisms.

My observations have seemed to relate to the oxygen level of the pond with the percentage of snails that were at different levels in the pond varied according to the oxygen level in the pond.

WHEN IT WAS 5 PPM NEARLY ALL OF THE SNAILS WERE ALL OVER THE POND.  wHEN IT DROPPED TO 3 PPM OR LESS MOST OF THE SNAILS WERE WTHIN A FEW INCHES OF THE TOP OF THE WATER AND WHEN IT DROPPED TO TWO PPM MOST OF THE SNAILS WERE NEAR THE SURFACE.  wHEN THE PPM DROPED BELOW 2 OR ONE PPM THEY WOULD NEARLY ALLBE FLOATING, ALIVE AND WELL, AND DRAWING THEIR OXYGEN FROM THE AIR RATHER THAN THE POND.

THIS CAME IN  HANDY WHEN THERE WERE OTHER FISH OR SHRIMP IN THE POND BE CAUSE WHEN THE SNAILS WERE ALL UP IN THE LATE EVENING IT WAS A GOOD SIGN THAT THE OXYGEN IN THE POND WAS ONLY ABOUT 3 PARTS PER MILLION. SO IT WAS A GOOD IDEA TO BEGIN AERATION OF THE PONDS WHICH COULD HOLD UP THE OXYGEN DURING THE NIGHT.

Their are also many other ways to judge the relative level of oxygen in a lake or pond such as the location of dragonfly larvae, mosquito fish other insects and any other critter that absorbed their oxygen from the water but had the ability to get more by reaching the surface.
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Related Posts

1. SKITTERING COMPARED TO TWITTERING
2. OXYGEN & AQUATIC LIFE
3. OXYGEN & THE HUMAN FISH
4. FINANCING AQUACULTURE PILOT PROJECT FOR BREAKTHROUGH DEMONSTRATION
5. RESEARCH ON OXYGEN LEVELS NEEDED FOR FOR VASTLY IMPROVED AQUACULTURE PRODUCTION

About the author

MIKE SIPE

I am 70 as of August 4th 2010.  I have spent over 41 years Breeding tilapia, improving tilapia gene lines creating Red tilapia, and improving the body form of "pennyfish" from 24% in 1963 to 50% in 2009. I have pioneered and installed high oxygen intensive aquaculture production  systems.   We (TILAPIA AQUACULTURE INTERNATIONAL) built the first u-tube used to control oxygen and co2 levels in aquaculture.   We can dissolve up to  800 parts per million parts of water and thereby control oxygen levels in growing situations. ( THIS IS WHAT MAKES OUR INTENSIVE CULTURE SYSTEM WORK SO WELL) We have designed hatchery systems to produce thousand of pennyfish fingerlings a day using breeder cages.   We have helped to establish the production of over two billion pounds per year of our tilapia in over 50 locations in North America, Mexico, South America, Central America, Kenya Africa, and Saudi Aribea in the Middle east.  Our goal is to help people with the production of tilapia necessary to *feed everyone* in the world a well balanced nutritious* diet, and to restore the forest of the world. If you wish to talk with me my phone number is 877 217 7006. Please feel free to call me during normal Eastern daylight times. At this particular time I believe that I have more hands on experience in building , designing and running u-tubes to lower the cost and risk for growing all kinds of Aquaculture by 10% - 20% and the cost of dissolving oxygen in an intensive system by 50- 85%. The safety issue is by far the most important issue because having complete control over the oxygen level in a tank helps to assure he safety of the crop and the cost. Another area where I have extensive experience is on what is required to create new characteristics in a gene line. We can take a tilapia that is black and turn it to a brilliant red or take a gene line and select for various body form changes or various internal genetics needed needed to manufacture certain expensive biochemical products..such as Heparin which is an important molecule in haemoglobin that plays a role in clotting blood. A good breeding and selection system could virtually increase the production of almost any biological chemical system in the tilapia.

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