"as a fiduciary of a trust can i deduct management fees from a brokerage acount"
Yes. The fees, however, are subject to the 2% AGI floor.
See https://www.irs.gov/instructions/i1041/ch02.html#d0e3466
[Note that this answer is no longer accurate due to the Tax Cuts and Jobs Act - taxpayers cannot claim miscellaneous itemized deductions]
Edited 3/29/2019
