If you're getting motion blur I assume it is because most of the light on the subject is ambient, not strobe. The strobe firing time is much less than 1/250th, so if all of the light was coming from the strobe you wouldn't get any blur. This may not be practical, but if you can crank up your strobe power and lower your iso or aperture you should get a little less blur because more light will be coming from the strobe. Of course this also means you'll have a very dark background, so it may not work in your situation. You'll also need strobes powerful enough to overwhelm the ambient light.
When I have shot sea lions this has worked because with our poor local viz the ambient light level was pretty low.