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Secondary Hi Removal

The practice of effecting cosmetic changes to animals is a much talked about subject and not everyone agrees with it. Amongst the koi fraternity cosmetic changes are made globally and most notably, by some of the most prominent breeders in Japan. For the hobbyist it is a personal choice. Given the fact that a hobbyist can only accommodate a limited number of fish during his lifetime and relatively few Tosai that he/she has carefully selected, will retain the specific attributes that led to the selection in the first place, decisions about cosmetic changes must sometimes be made. There are few options available to the hobbyist. Should the fish that has been raised and cared for be destroyed or passed on to someone else, while the chances are very good that the next selected fish will develop some other more serious defect?  It is also a known fact that no koi is perfect. So how many times should the hobbyist select a fish and then get rid of it?
 Koi are kept for their awesome presence, beauty and grace. Once a single irritating feature develops on a fish, much of the joy of keeping such a fish will disappear. I have therefore compiled the following for those hobbyists that may be interested in removing secondary hi or also known as “tobi hi” in order to keep a much loved pet. It is not a difficult process but such a procedure requires knowledge of the anatomy of a fish and reasonable skill and a few “trade secrets”. These “secrets” come with experience and no amount of reading can prepare the average hobbyist to execute the procedure flawlessly. I normally ask the fish owner to leave me alone during the procedure, because the questions and sometimes panic is distracting. Please note that during the process, an absolute hygienic situation must be maintained. The first line of defence against pathogens, namely the cuticle, scales and skin will be breached and if the hygienic conditions are compromised during the procedure, the resulting infection will ruin the fish, or even kill it.

This Matsunosuke Sanke developed secondary hi at the age of 18 months. It was initially thought that it may develop a Kanoko (dappled) pattern but at 30 months, on the 1st of June 2011, it was obvious that the secondary hi spots will not develop further and that it will just remain a bad case of secondary Hi. This secondary hi developed mainly on the right shoulder with a few discoloured scales also to the left of the dorsal area. 
     top_view         1_June_left_shoulder

On closer inspection, it was evident that the development of the hi and sumi plates are satisfactory and the Sanke exhibits good skin quality and shiroji. In light of the above, the owner requested that the secondary hi be removed. It is not a show fish, but the sentimental value warrants intervention. The following steps would be followed during the procedure.
The Sanke is bowled and when the appropriate dosage of Phenoxetol takes effect, it is moved to a smaller “operating” bowl with a smaller dosage of anaesthetic. Since the procedure is conducted next to the pond, we cannot utilize the normal pump that will circulate the anaesthetic over the gills, nor do we have the luxury of a decent operating table. The fish is therefore placed on top of a rubber platform surrounded by a few litres of water that contained the lower dosage of anaesthetic. Although we do not anticipate that the procedure would be conducted over an extended period of time, we will frequently place the fish in the water containing the lower dosage of anaesthetic, to keep it deeply sedated.  
We know that during the fairly invasive procedure there will be damage to the various epidermal layers so the starting point is to administer an intramuscular injection of a broad spectrum antibiotic. In this case, it is a combination of antibiotics that are effective against gram negative bacteria. The fast acting antibiotic is injected intramuscular while the slow release antibiotic is injected intraperitoneal.


A quick test is conducted to determine where exactly the hi is seated.


The scales of a fish are seated in pockets in the Dermis and emerge out of the connective tissue. In most cases of secondary hi, the pigment is contained in the outer edges of the scale pocket and can be easily scraped off with a sharp instrument. In this case we first tried to scrape the pigment off but unfortunately the pigment is not only contained in the outer edges of the scale pocket. The pigment is also visible within and underneath the scale in the dermis as demonstrated in the drawing below. The skin of a fish is divided into two layers, the Epidermis (outer) layer and the Dermis. The Epidermis is made up of Epithelial cells, arranged one above the other. Inter-spaced between the Epithelial cells are cells which produce mucus secretions that form the very important protective covering that we know as the slime coat. In the drawing below, the location of the pigment is indicated in orange

On closer inspection it is evident that the procedure would be more invasive than anticipated.


The two photos below clearly show the progress made when removing the scales and the hi pigment that remains in the dermis when the scales are removed.



With the scales removed, it is necessary to remove the hi pigment that remains in the slimy membrane that also contains the Epithelial cells.


It can be seen that the hi is seated much deeper than originally anticipated and the work on the fish must now rapidly continue




Time is of the essence but soon the hi is completely removed, except for three scales close to the dorsal area.
With all the hi pigment removed, the area is sealed with Pro-cure that contains propolis.


The fish is turned over to remove the same type of problem on the left of the dorsal area. The same procedure is followed.





Again it is sealed with Pro-cure.


When the Pro-cure has sufficiently set, the fish is released in a quarantine pond. The quarantine pond contains 5 gram of Virkon S per 1000 litres to keep the bacteria count low.

This is the progress almost 3 months later. The photo, taken on 28 August clearly shows the regeneration of scales. In this instant the scales are much thinner that the surrounding original scales and the stress of netting still causes a pinkish tint in the skin. The new scales are not yet the same size as the ones that were not removed, but in time it will regenerate fully! Fortunately the hi has not returned. There are a few spots that I missed, but it will be very easy to remove at a later stage. If everything goes to plan, the scales will be normal sized by the end of summer.


Please note, there are certain risks involved in this procedure. If the “root” of a scale pocket is damaged, the scale will re-grow in a distorted way or if the damage is severe, not at all.

29 October 2011. My final follow-up on the Sanke. She is now 63 cm and I must admit, it was worth the effort! A final few hi markings that need to be removed but fortunately they are on top of the scale. It will be removed in seconds.


Last Updated on Wednesday, 16 November 2011 09:47