In the last twentyfive years the population in Murmansk has dropped from some 420.000 to the current 315.000. Now I have read some more information why people had come to Murmansk back then: during Soviet times the harsh cities in the Russian north offered even 100% higher salaries than in the more comfortable places in the south, as well as longer and paid holiday reatrats at the Black sea, earlier retirement age, and extra food and clothing supplies. So although you had to sign contract for at least 5 years, the offer was too good to refuse.
So the city was constantly in flux, migrating, attracting new working force from around the Soviet Union. And it seems that although these times are (not so long) gone, the migrational nature of the city remains: peope come here for business, stay a couple of months or years and leave, sailors come and go, young people leave to study in the capital or in Norway; most probably not to come back. Who stays is the military, with their military bases surrounding the city, and the FSB, with the tall, large and substantial building making its presence very viable on the main prospekt Lenina.
And the nuclear reactors.
Murmansk has one of the highest amounts of operational nuclear reactors in the world. Beat that precedence, eh.