Shuristan culture responds to fear with extreme aggression, similar to their immune system, and they generally have less than no chill. I think the Mishhu knew this and are setting up shop in the moorings and foundations of Capricorn, hoping to not be noticed. I expect Shuristan civilians to start to go missing fairly shortly. So we might see a slight uptick in missing persons reports in the area, along with a slight decline in local agriculture. Nothing unusual or alarming. Squids be too smart for that.
As they adapt and spread, we may also see short term disappearances of Yamataians, and an employment of similar tactics to the Tyranid genestealer cults.
Also makes sense if the crab was a diversion, buying time for the initial setup by taking a major agricultural center with it, which pulls resources away from the actual problem. The loss of the Tskugani Dome was effective in creating a distinct division between the Civil Service and the Star Army, making communication and cooperation more difficult. This can obscure the severity of the threat.