I expected Apple’s trading volume to be heavy Wednesday because it was an investor’s last chance to own the stock before it went ex-dividend.

I was wrong. According to NASDAQ, only 8.7 million shares of Apple changed hands yesterday, 42% below its average volume of 15 million.

The action, it turns out, was in the options market. Trades in Apple puts and calls soared to 1.34 million contracts, Reuters‘ Angela Moon reports, more than double the daily average of about 600,000.

The game, according to optionMonster.com’s Jon Najarian, was to be on record as owning tens of thousands of Apple shares yesterday without shelling out hundreds of thousands of dollars. And it was played with deep-in-the-money calls.

“Traders buy those, sell them seconds later and exercise their right to turn the long call into stock, to trade into a long stock, short call position, trying to capture that $2.65 dividend,” Najarian told Moon.”With 937.4 million shares at a $2.65 dividend, that’s a $2.5 billion payout.”

That would explain, for example, why 120,860 January 2013 $300 calls changed hands on Wednesday. A lot of those trades went down just after lunch Wednesday — in blocks of 9,000 to 16,000 contracts of 100 shares each.

The theory is that if Apple’s share price drops $2.65 on Thursday — as these traders expect — so will the value of those short call positions. That way they collect the dividend without feeling the sting of the share price drop.

We’ll see how well that worked out when the markets open Thursday, the first day of ex-dividend trading.

UPDATE: Rather than falling $2.65, Apple closed up $3.52 (0.57%) Thursday. How that affected the speculators may depend on whether they decided to hold the stock more than a few seconds.