We do know that they have extremely slow reproductive rates, especially when compared to other cephalopods. Nautilus take perhaps 5 to 10 years to reach maturity and only lay a dozen or so eggs in a year. Once mature, Nautilus produce eggs over many years. This means that if their population is severely depressed it will take a long time for them to recover. In contrast, most cephalopods only live a year and produce many smaller offspring.
Many cephalopods only reproduce once and die.
At Dalhousie I've worked with nautiluses while investigating their activity patterns with Dr. Webber and Dr. O'Dor. I have to say, Nautilus are not much like squid, octopuses and cuttlefish. They are interesting for scientific reasons but they don't rapidly change color, are not as active and do not seem to be anywhere near as intelligent and responsive as the other cephalopods. They are basically swimming snails. These major differences are not suprisingly as they diverged from modern cephalopods before there were bony fish in the ocean.