The us fda will not recommend an average daily amount (only maximums) for omega 3 fatty acids but health canada has done some studies and they came up with 1000 mg.
Researchers have studied larger dose amounts (at least 3 grams) in patients with health conditions but there are no conclusive results at this time.
The us fda recommended maximum (for adults) is as follows:
total daily intake of epa and dha not to exceed 3 grams per day with no more than 2 grams per day from a supplement.
If you have no health problems then stay with 1000 mg per day but you need to look at how those 1000mgs are made up.
The actual omega 3 part usually comprises only 400- 500mgs and of this dha is the most important (and expensive) component (followed to a lesser degree by epa). Current recommendations for daily intake of dha is 220 mg but I think this is too low for this essential substance. The product I use has around 300mg.
Recently, research has begun to pile up which shows that dha offers greater cardiovascular benefits than epa. Originally it was thought to be the other way around which is why fish oil supplements always had more epa than dha (and most still do). Dha is important for brain health particularly for babies (including unborns).
So look for fish oils termed 'pharmaceutical grade'; as these are concentrated oils - this is what you want. Look firstly at dha content when comparing brands (at least 250 mgs up).
Also look for oil that is in an 'ester' form (not triglyceride form as most are) as this offers significantly higher levels of absorption in the body (fish oils in triglyceride form have to convert to esters before the body can use them!)
and don't forget to use an oil that is molecularly distilled (this removes all contaminants) - most manufacturers avoid this as the process is expensive - but the word is getting out now and I see more molecularly distilled oils appearing on the market all the time.
Cheers
brett