Very likely because Fe is an essential metal. It is used in haemomoglobin, and as a cofactor in many enzymes.

You are correct Gerardo Gold-Bouchot, however, Zn and Cu are also essential and also part of many enzymes and metabolic pathways :)

That is very true. However, the amount of metal in the blood is higher than in any other compartment, except of course Ca in the bones.

That is right and the ability of Fe to accumulated differ from species to the other but the main target of its accumulation is in liver

I actually have a question: I read that over 90% of Fe is reabsorbed in the intestine, would this be true, no excretion route is available??

A lot of liver enzymes use Fe as a cofactor

It means that Fe is already present in fish in high amounts. Now how can i work out that what will be the actual amount of metal accumulated from environment.

Iron in hemoglobin, myoglobin and enzymes is essential or housekeeping iron. Iron in ferritin is storage iron. The main stores are in liver and muscle and are measure by measuring tissue non-heme iron. Iron accumulated in excess of requirements is measured as this non-heme iron. Google 'tissue non heme iron' and you will find assays.

Thanks to all

If "its presence in the water is higher in comparison" with other metals you are monitoring, what further cause of its higher body burden in fish are you looking for?

Actually i want to confirm that whether the accumulated iron is only from water or fish already contains rich iron.

Fish excretion system is primitive compared to that of land animals, for instance. Therefore, it is expected we find that accummulation of such elements is higher in fish (pure physiological explanation) than in land animals. Iron (Fe) in particular is found in tissues rich of haemoglobin and myoglobin. In your case, Fe is the more abundant element in your fish samples. However, it is difficult to conclude that Fe is the more abundant element in fish in general as this depends on many factors (species, type of tissue, age, duration of exposure, contribution from the environmental, etc). Contribution from the environment plays a key role in metals accummulation (water, soil, air, etc.). In fish, metals in general accumulate mainly in liver, kidneys and gills.

I think it is difficult to generalize, I advise you to go through litterature regarding Fe concentrations in different fish samples and see if this is a general case.

Are these marine or freshwater fish? The speciation of Fe in water would suggest it is not readily available for uptake across the gill, so it maybe of interest to look at dietary food sources. In answer to Rachel's question there is no known regulated excretory pathway for iron and iron homeostasis is controlled via the regulation of uptake. The reason for potential higher levels of iron is likely due to the ability of fish, and all vertebrates, to store iron in a relatively non-toxic form in ferritin.

Once more: I still wonder why nobody pays attention to the fact that "also its (meaning iron's) presence in the water is higher in comparison" - obviously with Zn, Cu, and Cr. I think that one should rather look for sophisticated explanations if iron content of fish's tissues were NOT higher as compared with three other metals.

Heavy metals accumulation in fish body depends on enviromental condition and it accumulated via food chain and food web. in the waters, heavy metals deposited by industrial effluents, domestic pipes, natural weathering and other pollution reasons. According to your result, iron contents in water is higher than other minerals so reason is clear that iron accumulation will be higher in body.

Dear Jeteendra, if I understand you correctly, you agree with a simple answer to the original question I proposed long ago and repeated recently. So I am ready to upgrade yours.

dear javed, "Fe" is our common element in our blood and these organs(gills, liver, kidney) give more blood than other organs, because of that their concentration is higher than others! this is usual we have high concentration of Fe in organs such those...