I actually tried my best to get the standards of WHO and FAO for fish tissue and was unable to find it as I browsed WHO and FAO Websites. I will be very thankful if somebody can help me out.
Do you know this publication? EFSA European Food Safety Authority (2012): Scientific opinion on the risk for public health related to the presence of mercury and methylmercury in food. EFSA Panel on Contaminants in the Food Chain (CONTAM). EFSA Journal, vol. 10, no. 12, 2985-3326. Best regards, Lenka
Permissible Limit of heavy metals in fish tissue of L.rohita[Table-3] and C.striatus[ Table-4] as given by FAO(1983) and WHO(1985) SEE ATTACHED FILE[ZOOM200]
The heavy metals were accumulated at varying levels in different tissues of L. rohita and C. striatus. The concentration of heavy metals in different organs of fishes followed the decreasing order Pb > Cd > Zn > Cu >Cr > Hg.
a good paper for this question: http://ac.els-cdn.com/S2314808X14000256/1-s2.0-S2314808X14000256-main.pdf?_tid=238f33b0-9a6b-11e4-8d57-00000aacb35f&acdnat=1421074747_03c796cbae7b6fbdf9bb9bef216e44fe.