Options trading activity edged higher last month as more than 315 million contracts were traded in the industry's busiest June ever, according to a Wednesday report from the Options Industry Council.

The Chicago Board Options Exchange remained the biggest trading venue, though its average daily volume of 4.2 million contracts came in 14% lower than the year-ago period.

CBOE reported heavy trade in Apple Inc. (AAPL) options for the month, as the technology brand saw brisk sales of its new iPhone model and the return of chief executive Steve Jobs following a liver transplant; contracts on Citigroup Inc. (C) and General Electric (GE) were also popular.

The all-electronic International Securities Exchange, a unit of Deutsche Boerse's (DB1.XE) derivatives arm Eurex, was the second-largest options venue by volume with an average 3.9 million contracts changing hands in June, slightly higher than the year-ago period.

Both the CBOE and the ISE saw their market share slip from May levels, as CBOE claimed 29.3% against the ISE's 27.2%.

Smaller options markets operated by Nasdaq OMX Group (NDAQ) and NYSE Euronext (NYX) were seen gaining share, according to an Equity Research Desk analysis.

NYSE Euronext last week said it would reduce some options trading fees and eliminate others, hoping to increase volume.

The ISE maintained its lead in equity options with nearly 29% of the market, whereas CBOE continued to dominate index options activity, handling nine of 10 such trades.

Average daily trade across all trading venues topped 14 million contracts in June, according to the OIC, which tracks trading activity across the seven major U.S. options exchanges.

-By Jacob Bunge, Dow Jones Newswires; (312) 750 4117; jacob.bunge@dowjones.com