I regularly refer to suggestion that uptake of DHA is reported to drop off at about 2grams a day.
Here is a link to a "trial" on the subject and a graph.
As usual please discuss dietary changes with your medical advisor. Fish oil causes blood thinning and some other issues for a small number.
RB
http://www.ajcn.org/cgi/content/full/83/6/S1467
"DHA doses of {approx}2 g/d result in a near maximal plasma response. "
http://www.ajcn.org/cgi/content/full/83/6/S1467/F5