What could be a substitute for sunflower oil?

the one other option in this heat/smoke point range is flaxseed oil. i think with salmon, olive oil would work best though. olive oil poached salmon has been so popular lately because of how compatible the flavors are...so I think that would be your best bet.

Safflower or canola. Olive oil has a lower heat.

Safflower oil. Probably regular olive oil as well.