These large, modern [Chinese "fishing"] vessels represent a stunning level of sunk capital costs but do not engage in much commercial activity. Frequent satellite imagery shows that the vessels spend nearly all of their time anchored, often in large clusters. This is true whether they are inside the lagoons at Subi and Mischief Reefs or loitering elsewhere in the Spratlys. Operating in such close quarters is highly unusual and certainly not the way commercial fishing vessels usually operate.
Whatever you call it, China uses their maritime militia to bully South China Sea competitors.
And it really isn't a militia--it is really a force of ships with no civilian purpose. Militias are civilians called up from their civilian duties to fight.
This Chinese civilian "militia" is simply a poorly armed military force designed to overwhelm true civilian ships while daring foreign militaries to stop them.
UPDATE: RAND looked at China's "gray zone" warfare:
Examples of the grey zone tactics used by Beijing included the expansion of artificial islands, the use of coastguard vessels and maritime militia and “a group of civilian fishermen who receive military training and coordinate their actions under state and military guidance” to assert control over disputed islands and reefs.
The report said it had stepped up its use of such tactics in recent years against rival claimants such as Japan, Vietnam and the Philippines. ...
China was also accused of using non-military vessels nominally manned by civilian personnel as “maritime militia”. “These operators are in reality, naval reservists trained in naval operations,” the report said.
Will rivals send out their own "militias" to engage China in low-level warfare of ramming, fire hoses, and cudgel-armed boardings?