Byrum is the biggest town and municipal seat on the Danish island Læsø in Kattegat. The town is the only one on the island not located by the …Byrum is the biggest town and municipal seat on the Danish island Læsø in Kattegat. The town is the only one on the island not located by the sea. The town has a population of 440. Byrum is located in North Denmark Region, Læsø Municipality.