I doubt that. Bears are worse at defending themselves than, say, Bison, and if bison got wiped out (which we don't know if they are, we haven't seen much of North America to be honest, and European and Caucasus bison were extinct or nearly extinct before the resonance cascade), then bears...
Most animals living in water below 1000 m probably survived. None of the aliens we have seen are even remotely capable of surviving under such pressure, and ichtyosaurs clearly also need light (also, we have no indication there is water that deep on Xen or other places). Some remote islands may...