The Austrian said the son of seven-times world champion Michael Schumacher was a great addition because of his race experience with Haas for the past two seasons and tyre knowledge.
"I hope these guys (Hamilton and Russell) don't have a fish poisoning," Wolff said at the Silverstone launch of the team's new W14 car.
When Hamilton, a vegan, pointed out that he did not eat fish, Wolff corrected himself: "avocado poisoning".
Schumacher has been replaced by experienced compatriot Nico Hulkenberg at Haas and will spend much of his time in the Mercedes simulator when not at the racetrack.
The German also recently tested a Formula Three racer and said he planned on driving cars from various categories to keep his hand in.
"This year, I decided that I wanted to be as fit as I've ever been, which I feel I have achieved so far, and I'm still planning on getting even fitter until the beginning of the season," he added.
"Driving wise I'm still in the loop, very much, and I'm planning on staying there."
