The 23-year-old batsman, who had to be escorted away by police, hit the fan last week after he verbally abused him by chanting "Ashraful bhua" (Ashraul rubbish) as he trained at an indoor stadium in the capital Dhaka.
"He appeared at a disciplinary hearing of the Bangladesh Cricket Board (BCB) in relation to his involvement in the incident," the board's spokesman Rabeed Imam said Monday.
"The board concluded that Ashraful's action was in gross violation of the BCB Code of Conduct and decided to deduct 25 percent from his retainer for the month of March 2008," he added.
Ashraful, whose team suffered a 3-0 whitewash at the hands of the visiting South Africans early this month, later apologised for the incident.
The diminutive cricketer, appointed captain last June after some stunning batting in the Cricket World Cup in the West Indies, has been in poor form recently, managing just 17 runs in three matches against South Africa.
"His latest act supported the growing concern that the little right-hander is just not strong enough to tackle the intricacies of a post that requires a cool head," the English-language newspaper Daily Star said immediately after the incident.
The BCB also deducted 20 percent from the monthly retainers of vice captain Mashrafe Mortaza, spinner Abdur Razzak and pace bowler Syed Rasel for playing in an unapproved match in a western Bangladesh town.