There are typically three stages of G.A.S.

In the first stage the fish is presented with a survival decision- fight or flight? Koi can’t fight of course, but they can ‘resist’. Net a koi, handle a koi or bag a koi and they WILL FIGHT YOU! This is when ‘we’ become a stressor. Koi have no teeth, claws or spines to fight with , so except for a lashing of a tail ( an escape technique really) koi are almost all about ‘flight’.But what happens when a koi can’t flee? And what happens inside when a koi decides to flee?

In the past we’ve talked about how koi are made up of fast and slow muscle and how one is for busts of speed and the other for the long haul swimming. In the ‘flight’ mode, these muscles become supercharged when the autonomic nervous system stimulates the release of adrenaline from a gland off of the kidney. That is easy to understand and appreciate as we all have felt the effect of adrenaline. But what is more subtle is the fact that at that moment other systems are deprived as all the effort is directed towards fight or flight. In our koi at that moment in time, all nutrient and oxygen reserves are sent to the escape effort, meaning none of that is being used in a routine way. In other words, no healing or digestion is taking place in that moment. This is trade-off and meant to be an effective short term event in which survival is more important than routine. And it is important to understand that ‘flight’ does not always imply physical danger. Flight can also be a desire to ‘runaway from’ or escape bad water, toxins in the immediate surrounds, freezing temperatures, pH crash etc. And in nature, of course, the fish can simply swim away to another area of the river, lake or pond.

But what happens if the challenge does not go away? As in ammonia laden water or chronic cold or heat? Stage two of GAS begins.

In this stage, the fish will attempt to adapt to the chronic stress. This may be somewhat possible or not possible at all. But the body will try. In this process huge hormonal and cell changes will occur. In time these hormones will begin to actually damage internal organs and systems. Ironically, these hormones designed to protect, short term, become the suppressor of the general health of the koi, including the suppression of the all important immune system. For example, the constriction of blood vessels in Stage one, a good plan for rapid escape, lead to blood pressure issues in stage two. The demand for ‘sugar’ energy in the circulating blood leads to blood glucose issues in general. Salt retention begins and potassium excretion increases. There is a general increase in protein metabolism at a time when feeding is not likely. In other words, all systems within the fish abandon normal metabolic function in favor of adaptation. This might buy some time for the individual fish until conditions improve, or unfortunately may lead to stage three.

Stage three- very few koi will survive stage three without direct intervention. In this stage, the shift in metabolic direction is either too great or just lasted too long. The immune system is shut down so infection or infestation is a likely cause of death in many cases. The best characterization of things at this point is one of complete physiological exhaustion. This can be seen in the now depressed fish that has begun to lose equilibrium due to general osmotic regulatory function.

Hopefully this post will put some logic to why we use things like darkness, optimal temperature zones, neutral pH, massive oxygen, mild salt and withhold normal feeding ( fresh protein only and sparingly) to improve water quality when we have a fish in GAS mode ( Stage one or two)

Running long- JR