Instinet said it handled 43 percent more volume in the trading of stocks in the United States in August, compared to July.

The agency-only broker and developer of electronic trading technology said its U.S. brokerage subsidiary had average daily volume of 431 million shares. In options, average daily volume was 363,000 contracts.

The firm set a record of 613,000 contracts in a single day on August 8. That was the second day of trading after U.S. debt was downgraded for the first time ever by a major ratings agency.

“In August we continued to see strong growth in both US equities and options volumes,” said Jonathan Kellner, President of the Americas at Instinet. “While volumes were up Street-wide, we were particularly pleased to see our core institutional flow surge to the extent that it did during the month, indicating that the buyside continues to look to Instinet as a safe harbor during periods of extreme volatility.”