DOC, my major was in electrical/electronic, but as a controls engineer I had to interface with hydraulic systems, mainly opening and closing valves, turning on and off solenoids, and monitoring pressures that allowed the oil to flow and move cylinders on a piece of machinery.
Usually hydraulics are used to move heavy objects that require higher torques, using fluids like oil to do this, the problem is that the oil gets dirty and needs changing, just like in a car. Electronics are used to move equipment that require lower torques and more precise movements. There are pluses and minuses in using both hydraulics and electronics, and most manufacturers use a combo of both.
As far as the pontential job market for a hydaulic engineer, I think his school would have knowledge of this, or he could Google it.
Doc, I think the engineering field is a great place to work, there's so many diverse job classifications that allow you to work with both hardware and software, you get to work with your hands and mind, and the pays not bad either, this along with it being honorable work.
And I think we need more engineers and less lawyers in this country.
Craig , you are doing the right thing asking your question in the field. Colleges often do not give the students the right picture. See the lawyers who sued because they felt that they got a too rosy picture in college.
The son of a friend of mine worked with hydraulics on an aircraft carrier as a mechanic. John Deere hired him and paid his college education to become an engineer. Looks like a good demand to me , but I have lost contact to be of any help.
B should talk to folks who actually work in this field right now ,they have the best answers about the real world and job satisfaction which is very important. Demand alone does not have those answers.