[Sandy Nelson]

Last year i got this fish off the middle river





I noticed at the time it had a yellow spot on its belly, i know when the river used to get stocked they used to put a blue spot on the trouts belly and wondered if perhaps the spot can fade over time and become yellow.
I didn't really think much else about it until the other day when i got another fish and it also had a yellow spot on its belly
It was almost the same size as last years one and would be about right for a grown on stockie



Anyone else noticed yellow spots on the bellies of fish, or have an empirical evidence that the blue spot can turn yellow over time, or perhaps even knowledge of fish being stocked with yellow spots.
I'd be interested know

Cheers

Sandy

[Allan Liddle]

Not 100% on this one Sandy but always thought the blue spot simply faded away.  have found fish with coloured markings on the belly before, many of them in places not stocked, so can only assume it's a natural mark?  Maybe more caused by fish having damaged or lost scales in this area and the recovery scales simply coming in a different colour?

Pure guess this though.

[Rob Brownfield]

I found this http://fishbull.noaa.gov/953/thedinga.pdf

Blue appears to remain pretty constant and does not show signs of fading after 33 weeks.

Orange marker does fade in that time.

Not conclusive, but studied in this experiment.

[Sandy Nelson]

I found this http://fishbull.noaa.gov/953/thedinga.pdf

Blue appears to remain pretty constant and does not show signs of fading after 33 weeks.

Orange marker does fade in that time.

Not conclusive, but studied in this experiment.

That is a very interesting study, cheers Rob

I was thinking more like 3-4 years rather than 33 weeks based on the size of the fish, so i doubt anyone has data on that.
Will keep my eyes peeled for more fish with marks and see if there is any consistancy.

Cheers

Sandy

[Rob Brownfield]

I spoke to my better half last night as she does work with a fish lab (Yes, they test long term effects of chemicals on fish, the evil woman!!) .

She suggested that even if the dye was permanent, it would disperse over time due to growth. If we are talking 3-4 years she suggested that the “spot” would be large, faded and the edges not clearly defined.

I see her point.

Interestingly (well, to me anyway), the tropical fish trade came under fire for colour injecting Glassfish with dyes to change their colours. The practice is now banned in the UK although the fish are still available freely  The dye lasted about 6 months or until the fish died, which was normally quite quickly. There were even attempts to tattoo fish in the US using lazer dyes. The "scientists" who came up with the idea wrote messages on the sides of fish. Sick!