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To dye or not to dye
Joseph P. Azzopardi
As a fish breeder and keeper I am amused to see the increasing rate of which dyed or painted fish are imported in our market and aquarium hobby shops.
Many fish keepers, and possibly even the traders, may not know the truth behind these painted fish. The practice of dyeing or "painting" the fish seems fairly innocuous and the artificially dyed specimens are certainly very eye-catching in their various "day-glo" colors. My investigations have revealed the truth behind the dyed fish .
Our first encounter with dyed fish was back in the late 1980's. Thousands of artificially colored glassfish, Parambassis ranga (formerly Chanda ranga) were imported into the UK.
The glassfish, so named because of its naturally semi-transparent body, obviously makes it an ideal subject for "painting".
They were seen with fluorescent shades of blue, purple, red, yellow, orange or green produced by dyes.
They were (and still are) imported under the names "painted glassfish" or "disco fish" (presumably because their almost fluorescent colors resemble discotheque lights).
Intrigued as to how the dye was applied we decided to carry out a little research. A few colored glassfish were sedated in MS222 anesthetic and observed under a binocular microscope. It became apparent that the dye is not on the surface of the fish, but lay under the epidermis.
Furthermore, the dye appeared fluid and could be moved slightly by gently squeezing the colored area.
This suggested that it must have been injected into the fish at various sites over the body in order to form the distinctive colour patterns. My fears were confirmed a few years later when I saw photographs of the colouring process on a prominent fish keeping magazine, revealing that each fish is individually injected using a syringe and needle.
The practice of dye injection is undertaken by fish farmers in some regions of Asia (but not Singapore as far as we know). Clearly, the common name "painted glassfish" is a cruelly misleading description.
If one considers the relative bore size of the injection needle with that of a glassfish, it would be the equivalent of us receiving several jabs using a needle of pencil-sized diameter - not a pleasant thought.
As experienced fish scientists told us, one would never dream of injecting fish of such small size. No wonder the injection process is alleged to cause high mortalities.
A survey which we carried out in the south of England revealed that over 40% of painted glassfish appeared to be suffering from lymphocystis virus. This disease manifests itself as small whitish growths on the fish's body and fins.
It is possible that the injection process increases the risk of this disease, perhaps by transmitting the virus from fish to fish via the needle (the same needle is used to inject tens or even hundreds of fish).
Alternatively, the stress of being injected with the dye may lower the fish's natural immunity to lymphocystis.
It must be said that, in our experience, those glassfish which survive the injection process go on to live fairly normal lives, despite the gaudy dyes present within their bodies.By time, the dye fades.
Many people believe that fish do not feel pain and so injecting them with dyes is perfectly acceptable. In fact, increasing scientific evidence suggests that fish are indeed capable of feeling pain, though we have no way of telling whether they perceive painful events in the same way as we do.
So dye injection is likely to be a painful experience for the poor glassfish. In fairness, many traders and hobbyists were mislead, just as we first were, into thinking that these fish were simply painted with the dye.
Now that the truth is out, it's time to stop this cruel practice, once and for all.
Glassfish are not the only species which are subjected to artificial colouring.
Many types of albino fish also make ideal "white canvases" for colouring. In the UK the following artificially coloured fish were noticed and suspect there may be others.
Albino versions of Corydoras catfish, such as aeneus; Tiger barbs; Albino Epalzeorhynchus (formerly Labeo) such as the Red-finned shark; Black widow tetras; Rams and some Botia species.
Practical Fish keeping magazine ran an award-winning campaign which started in 1996 and asked aquatic retailers to sign a pledge that they would not sell dyed fish. The majority of British retailers signed up and dyed fish are now relatively uncommon in the UK.
Now its our turn all fish lovers of the Maltese islands to do the same and ban buying dyed or painted fish.
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