Despite a growing pool of job seekers on online job boards and social networking sites, employers say candidates for high-level positions are getting harder to find.

Of 775 recruiters recently surveyed by the Adler Group, an Irvine-Calif.-based recruitment firm, three-fourths said there weren't enough qualified candidates applying for top staff openings. Sixty-three percent said the quality of candidates on major job boards was declining, while 60 percent said hiring managers weren't devoting enough time to recruiting efforts.

"When you compare the results of this year's survey to pervious years' results, it's clear that the situation is getting worse, not better," Lou Adler, the firm's president, said in a statement.

He added that finding skilled technical workers, such as scientists, engineers, health-care workers and software developers, was becoming particularly difficult.