Having lived for many years in Scandinavia,I have never really understood why it is deemed neccessary for a closed season at all.In most countries coarse continues all year round and just to add,in Scandinavia,they eat Perch and Pike!!
This closed season does seem very out of date and,dare I say,typically British from the century before last.
Oh and by the way,the fish still spawn and thrive even there.