How does General Zaroff lure people to play his game in "The Most Dangerous Game?"

There's no real evidence how many men General Zaroff has hunted down in the Richard Connell short story "The Most Dangerous Game." We do know that Sanger Rainsford is not Zaroff's first intended victim since Rainsford heard gunshots before falling off his yacht (although the shots may not have been intended for a human victim), and later he heard screaming and more gunfire as he swam toward the island. Rainsford discovers the terrible truth following dinner when Zaroff tells him

"We'll visit my training school," smiled the general. "It's in the cellar. I have about a dozen pupils down there now. They're from the Spanish bark San Lucar that had the bad luck to go on the rocks out there. A very inferior lot, I regret to say. Poor specimens and more accustomed to the deck than to the jungle."

Zaroff's lure is his home, Ship-Trap Island, which has apparently claimed many ships over the years. No one volunteers for service, but Zaroff is always awaiting shipwreck survivors to swim ashore and provide him his unusual entertainment.