fur shedding

[Chris m]

I have about a 2 to 3 year old rescued dog. He appears to be a short haired lab crossed with something else like a husky etc as he has white eyes and loves to pull me on my bike. He appears to shed significantly year round. Is this normal? I was under the impression that short haired dogs did not shed hair so much. One can grab the fur and pull chunks out. I brush him constantly and get an extreme amount of hair. I have no idea if this is normal. He has had all shots etc and is well looked after.