Subject: Why does vegetable oil smell like fish?

A while ago I put some vegetable oil (rapeseed) on my pasta and the smell of fish was so bad I had to throw 
it away. I've also had the same problem when frying with it. It seems to be related to heat, as cold oil in the 
bottle does not smell or taste of anything. Is it to do with vitamin E in the oil reacting as it is heated, or as I read 
in another answer, related to the fact it breaks down at a low temperature (oxidative rancidity). Maybe it 
contains enzymes that are activated by heat?

Thankyou.

Re: Why does vegetable oil smell like fish?