America's start-ups are hiring, according to a recent report, but talent is hard to find and expensive to keep.

Silicon Valley Bank recently published its 2013 Startup Outlook Report, based on a survey of 750 start-up executives from across the U.S. in the software, life science, hardware, and clean-tech sectors.

Its findings: While 87 percent of start-ups said they are hiring, the same percentage of them said that it is somewhat or extremely difficult to find skilled workers that they need to grow their business.

And not surprisingly, 82 percent of the companies said that they are looking for employees with STEM skills.

The survey showed that nearly 20 percent of the start-ups hope President Obama will help the talent shortage by reforming immigration policies. The current immigration rules make the process of hiring foreign tech talent costly and risky, although almost half of the start-ups have at least one foreign co-founder, according to the report.

Another challenge for start-ups, however, is competing with big-named firms, as engineering salaries continue to rise.  The average annual engineering salary rose to $118,900 in 2012, an increase of 3.7 percent from last year, according to a report from Riviera Partners, a San Francisco-based technical recruiting firm.

Engineers with the highest pays are those who specialize in database and back-end development. Interestingly, junior and mid-level engineers who did not attend top schools earned higher average salaries than those who attended top schools. But at the senior and management levels, top-school-educated engineers earned slightly higher salaries.

“Big companies are competing for cash, and start-ups are competing for equity,” said Ali Behnam, cofounder and managing partner of Riviera Partners. “You are playing for the hope that the venture you are working for will be a great success.”