In discussion I heard someone say that cleaner wrasse will sometimes eat the protective slime coat off of fish when they are alone, but when other cleaner wrasse are with them they wont because the others will punish them, which suggests they may experience shame or have a sense of socially appropriate vs inappropriate behavior, but I haven’t verified that fact with any reputable sources yet so take it with a grain of salt

I recall also hearing, I think from a DW documentary on fish intelligence, that cleaner wrasse will have different “tiers” of customers, where big predators get the fastest service, then visitors from another reef, and then the locals who don’t have anywhere to go, and that cleaner wrasse are more likely to take bites of the protective slime off of the “lower tier customers.” I also recall that they’ll give a soothing little massage immediately after taking those bites to keep their customers calm.

Fish cognition is really so underappreciated.