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Basis of colour difference between wild and cultured fish

The work undertaken gave the opportunity to define the coloration pattern of wild red porgy and to characterize the major difference in skin colour between reared ans wild fish.

It was found that:
- There is a significant dorsoventral gradient in skin brightness in both wild and reared fish, with the dorsal area being less bright than the ventral one. A similar gradient was also observed in melanophore density (number of melanophores/mm² skin) and in the skin melanin content.

- There is a significant difference in all chromaticity parameters between wild and reared red porgies especially in the dorsal body area and the tail. Wild fish display a bright pinkish hue (mean dorsal: L=60, Hue=66°, Chroma=11; mean ventral: L=60, Hue=78°, Chroma=12) while cultured fish display a dark gray colour (mean dorsal: L=35, Hue=34°, Chroma=3). Thus, the basic difference between wild and reared fish is mainly to the amount of light the colour reflects or transmits (L) and to its saturation (Chroma) and to a less extend in hue (the attribute of colour as found in its pure state in the spectrum). Colour differences were also found in wild fish of different origin, indicating possible differences due to habitat or size/age.

The basis of the difference in skin colour between wild and (non-carotenoid fed) reared red porgy is due to:

- Differences in the type of dermal chromatophores; wild fish skin contain melanophores, iridophores and xanthophores while reared fish skin only melanophores and iridophores;

- Differences in the size and shape of melanophores; melanophores of reared individuals were in the dispersed state;

- Differences in skin melanin content; reared specimens contained approximately 3 times higher melanin content than wild fish;

- Differences in the amount and type of carotenoid present in the skin; Wild red porgy contained predominantly astaxanthin diester, astaxanthin monoester and free astaxanthin (approximately 50% of the total carotenoids, contributing to the red hue) and unidentified “yellow” carotenoids (approximately 47% of the total carotenoids, contributing to the yellow hue). Reared fish contain either none or an extremely weak “yellow” band.

Reported by

Hellenic Centre Marine Research
71 003 Heraklion
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