There's no skills shortage, there's simply an inability of companies to consider investing properly in training their employees. Years of downsizing, and the consequent lack of loyalty from employees, will do that to a company.
Whether there's a shortage or an oversupply depends on where you look, and at what experience level. If you're a mid-career engineer, things aren't so bad. If you're early or very late in your career, you could be in trouble. If you're a company looking for people with 10-20 years experience in a particular specialty, willing to take a 3 month contract at an average full-timer's salary, perhaps there's a shortage of takers- particularly if it's in an area of practice which was in massive retreat and wasn't hiring new grads 10 or 20 years ago. (Stands to reason, doesn't it? But some companies in this situation scream "shortage" and politicians listen!) If you're a recent grad or recent immigrant engineer currently looking for work in Canada as an engineer, most particularly Ontario and most particularly Toronto, things are pretty bleak.
As to the original post: civil, mechanical, chemical and electrical are all mature fields now. Computer was flamed out here five years ago and still hasn't recovered. The others (geo, aerospace, environmental etc.) are really just sub-specialties of these, suffering from the vaguaries of supply and demand common to narrowly focused disciplines. They boom, but they also bust.
Is bio-engineering hot these days? The same rumours of this field being "hot" were circulating 20 years ago and it's no more true now than it was then in my view. "The next big thing" has been used by the business community as an excuse to increase engineering supply and reduce wage and working condition pressures on engineering employers for the past 20 years. "The next big thing" changes yearly to keep the politicians in a perpetual state of worry. Now they're adding the "baby boom" demographic shift as an excuse to keep the oversupply going, even though these folks won't retire en masse for at least another 10-20 years.