Well, I suppose you could try and derive something from logic.
What are the systems a cruiser has? Sensors, weapons, comms, engine, radar dish?
Sensors presumably takes about 10 people max to operate. Weapons? About the same, perhaps 15 if we're being generous. Comms? Perhaps 5 people. Engine? 8-12? Radar? Let's tie that into sensors.
That gives us about 40-45 people. Now we add logistics and maintainance staff, about 20. Now we add the bridge crew of about 10. 75 people 'round about. Plus a repair crew? 10 people. 85 people.
Keep in mind, when making a carrier comparison/contrast, a Fenris doesn't have pilots, or aviation techies. It doesn't have associated aircrew officers, it definetely does not have a large marine complement. It doesn't have a crew large enough to quantify 100 people paid to peel potatoes. It doesn't need a large bridge crew. It doesn't have a large deck that needs people to coordinate it, it doesn't have any large places besides the enlisted mess that needs people to clean it.