Daly (67) was followed by K.J. Choi (68) and Jason Day (68). Six players, including 1999 British Open champion Paul Lawrie and Nicolas Colsaerts, were three shots off the pace.
Martin Kaymer (71) and Sergio Garcia (72) were in contention, but about two-thirds of the field shot over par, including defending champion Thomas Bjorn (79).
“It just happened,” Fernandez-Castano said with a smile. “It was such a difficult day that you didn’t have any expectation going out there. Every shot was difficult. Every shot, you had to be 100 percent focused. That is probably what kept me in the game.”
Daly benefited from milder conditions in the morning when gusts of up to 22 mph died down for several holes. The two-time major winner was bogey-free, with five birdies.
“It was brutal. I’m pretty shocked myself shooting 5- under,” said Daly.
“It was great start,” he added. “It was one of the best rounds I ever played. I mean that. That is just how hard the golf course is playing.”
LADIES EUROPEAN TOUR: In Gold Coast, Australia, Lee Bo-mee, of South Korea, shot 7-under-par 65 to take a one-stroke lead in the Australian Ladies Masters.
U.S. Open champion So Yeon Ryu was a stroke back with fellow-South Korean Hee Kyung Seo and Christel Boeljon of the Netherlands.
Lexi Thompson shot 67.