They used a laser to blast the fish. Barbaric doesn't even start to describe this practice...
On a side note, I probably could finally create my avatar for real
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Production methods
Dyed fish have been on sale in the aquarium hobby since the 1980s, and were previously produced by injecting acrylic paints or dyes into the body cavities of fish using hypodermic needles. New forms of dyed fish have entered the UK aquarium hobby in recent years bearing much more intricate patterns of dye, but suppliers in the Far East have remained tight-lipped about the techniques used to produce the fish.
Dr Alex Ploeg, Secretary General of Ornamental Fish International, told Practical Fishkeeping: "The topic of dyed fish is one that is being discussed within OFI on an ongoing basis. However, it is proving exceptionally difficult to obtain direct information on the techniques used.
"Being ever-conscious that we cannot enforce any worldwide restrictions on the industry - we actively take steps to emphasise to our members that OFI is against any practices that are unethical or embody negative welfare aspects".
Although tattooing has previously been suggested as a possible method of applying intricate patterns of dye to fish, this is the first official confirmation from within the aquarium industry of the techniques being used to mark these particular fishes.
It is not yet known whether some recently imported dyed fishes bearing similarly complex patterns of coloured spots, coloured stripes and even "lipstick" were produced using this technique, but most aquarium industry experts believe that all forms of dyeing are both unethical and unnecessary.
Welfare issues
Dr Peter Burgess, a fish health consultant whose work on dyed glassfish was published in Practical Fishkeeping in the 1990s, told us:
"The skin of a fish is living tissue throughout. Any colouring method that damages the skin's protective surface will render fish prone to potentially life-threatening infections.
The artificial colouring by laser presumably involves restraining the fish out of water for some time and this is likely to cause further unnecessary stress. And how do we know it isn't painful?"This practice should be condemned as being cruel and totally unnecessary..."
"This practice should be condemned as being cruel and totally unnecessary. It devalues living creatures and treats them as if they were some inanimate object that can be decorated purely for whim or commercial gain. For too long, fish have been widely perceived as cold, unfeeling creatures that do not perceive pain, but we know this is far from true. This despicable practice only serves to perpetuate the myth."
Dye lasers
The techniques being used to tattoo the fish in Hong Kong could be similar to those already in use by fisheries scientists to monitor the movements of wild fish.
The technology dates back to 1975, when it was first used on catfishes. Later work by Lee Blankenship and Dan Thompson of Washington Department of Fisheries in 1993 investigated the use of Coumarin Dye (CD) lasers for tagging wild salmonids.
Blankenship and Thompson found that the initial blasts from CD lasers tore away scales and the epidermis down to the surface of a layer of tissue called the stratum compactum.
Their research suggests that acoustic damage tears away tissues from the margins of the hole, rather than burning the area as some other lasers do.
The end result is that pigment cells above the stratum compactum are removed, effectively bleaching the area, and allowing it to be dyed using the pigment in the lasing medium.
When used on salmon, the damage from a CD laser can last up to five weeks. Blankenship and Thompson said:
"The epidermis recovers from the laser blast quickly. It closed within a week over all but the very largest injuries, which are completely re-epithelialised a few days later. The upper layers of the epidermis remain open textured for some time as a function of the underlying connective tissue injury, but return to normal morphology after about five weeks."
Fish with darker colouration need 4-5 blasts from the laser to bleach their melanophore pigment cells, which causes massive blistering beneath the stratum compactum.