Florida fund manager Arthur Nadel pleaded guilty yesterday to operating a seven-year fraud, admitting to defrauding investors in six funds and costing them $162 million.

Nadel, appearing in Manhattan federal court before Judge John Koeltl, pleaded guilty to all 15 charges he faced in an indictment, including mail fraud, wire fraud and securities fraud.

Under terms, Nadel, 77, has agreed to forfeit the $162 million in gains as well as several properties and other valuable assets. The plea agreement calls for a sentence of between 12½ years and about 24½ years in prison. Nadel will remain in custody, as he has since his arrest, until sentencing.

He admitted to taking investments from clients, issuing false statements about the funds’ performances and using the money he was supposed to be investing for his own personal use.