August was the first full month in which the nation's second-largest gambling market was competing against table games offered in neighboring Pennsylvania, whose slots parlors have been siphoning off Atlantic City's revenue for nearly four years.
The shore resort's 11 casinos took in $347.5 million in August, down from $391.7 million in August 2009.
Slots generated $245.1 million, down 11.3 percent, and table games accounted for $102.4 million, down 11.4 percent from a year ago.
For the first eight months of the year, the casinos won $2.5 billion, down 8.4 percent from the same period in 2009.
Friday's bad news arrived as New Jersey lawmakers were holding the second in a series of hearings on the future of the state's casino and horse racing industries. Gov. Chris Christie has proposed ending state subsidies for horse tracks and opposes letting them install slot machines as tracks in other states have done.
The struggling casinos vehemently oppose racetrack slots, arguing they can't absorb an even further revenue loss.
All 11 casinos saw their revenues fall in August, ranging from Caesars Atlantic City (down 5.7 percent) to Resorts Atlantic City, which was sold last month to veteran casino executive Dennis Gomes and developer Morris Bailey for the fire-sale price of $35 million
by far the lowest price paid for an Atlantic City casino. Its August revenues were down 21.2 percent.
Other declines were seen at Harrah's Resort Atlantic City (6 percent); the Showboat Casino Hotel (7.5 percent); the Trump Taj Mahal Casino Resort (8.3 percent); the Borgata Hotel Casino & Spa (11.7 percent); the Tropicana Casino and Resort (13.9 percent); Trump Plaza Hotel Casino and the Atlantic City Hilton Casino Resort (both down 14.5 percent); Bally's Atlantic City (14.9 percent); and Trump Marina Hotel Casino (20.4 percent).