Fishes and social contracts

In Part V of What a Fish Knows, Jonathan Balcombe writes about fishes in a community—with company/tank mates or in a shoal or school of fishes. You now may ask, do fishes recognise each other? They do. Fishes may have patterns that are only visible in UV light. Balcombe says, fishes have individual recognition, memory, and preference about whom they choose to swim with; they also have personalities. Do they recognise human faces? People who have pet fishes say yes.
Yesterday I made a video about fish watching, using my footage of The Deep (aquarium in Hull). Watch who swims with whom.



Now, to get back to the book, the most fascinating section of Part V is when Balcombe writes about social contracts among fishes—consider the cleaner-client symbiosis of fishes.

“The system works as follows. 1 or 2 cleanerfishes signal that they are open for business. They work at specific locations, and may use swimming postures and bright colours to enhance the signal’s visibility (a fish’s version of the rotating red-white-blue cylinder outside a barbershop). Other fishes of various types congregate at the cleaning station, where they wait their turn to be serviced by the cleaners. […] [Cleaners] pick over the clients’ bodies, removing parasites, dead skin, algae, and other undesirable blemishes. Clients benefit by receiving a spa treatment, including parasite removal. Cleaners get fed.”

So which species are they?

“Marine cleanerfishes include many wrasses, some triggerfishes, butterflyfishes, discus fishes, damselfishes, angelfishes, gobies, leatherjackets, pipefishes, sea chubs, surfperches, suckerfishes, jacks, and topsmelts. Freshwater cleanerfishes include cichlids, guppies, carps, sunfishes, killifishes, and sticklebacks. Some invertebrates, including several shrimps, also provide cleaning services. Client lists number well over 100 known fish species, including sharks and rays. Other clients include lobsters, sea turtles, sea snakes, octopuses, marine iguanas, whales, hippopotamuses, and humans.” 

Regarding humans, in Asian (I think Chinese) spas, people can dangle their feet in pool for cleanerfishes to pluck over.

“This is a dramatic scene if the client is a large predator. Although a shark or a moral eel could easily snap up the cleaner for a quick snack; it just isn’t savvy to eat your service provider.
But it is kosher to show consideration toward them. […]
Grey reef sharks invite cleaners to service them by angling their bodies upward and opening their mouths wide. The cleaners show no fear as they enter the shark’s deadly cavern. They seem to know that this massive predator, hundreds of times their size, means them no harm.”

Isn’t that so interesting?
The relationship between a cleanerfish and their client is also not random.

“It is built on trust, and cultivated over weeks or months. A social contract such as this requires that individual cleaners recognise their clients. With dozens of clients per cleaner, cleanerfishes maintain an impressive mental database of clientele. In choice experiments where a cleaner could choose to swim near 1 of 2 clients, the cleaner spent more time near a familiar one. […]
In addition to remembering whom they cleaned, cleaner wrasses can also remember when they cleaned them. They are more likely to give precedence, say, to a particular triggerfish client who missed their last appointment, because that client will probably have greater parasite buildup.”

These fishes can use memory along 3 dimensions—who, when, and what. They demonstrate episodic memory.

“If a fish can track past events, might she also be able to predict future ones? […] Roving cleaners are more cooperative with their clients near the centre of their home ranges, where they are more likely to reencounter client fishes. They do less mucus nipping and cause fewer ‘jolts’ in their clients during cleaning interactions.”

This is like our behaviour—human beings are more cooperative with a partner when we’re likely to interact with them again. Doesn’t this make you look at fishes in a different way?
Now, just as in the business world of human beings, there can be conflicts, cheats, and frauds, there are equivalents in the fish world.
The conflict between cleaners and clients is because cleaners most like to glean from the mucus, which has more nutritional value and might taste better than algae and parasites, and clients wouldn’t like this.

“A jolt happens when a client flinches as a cleaner nips at the protective mucus layer that surrounds a fish’s body.”

Consequently, cleaners give clients some tactile stimulation.

“They do this by facing away from the client and stroking them with rapid movements of their pelvic and pectoral fins. This caressing behaviour seems to be done for 2 reasons: (1) to encourage a client to stay longer at the cleaning station, and (2) to mollify a client following a jolt. Cleaners are more likely to caress a predaceous client, probably because it lowers the risk of an aggressive chase from a potentially dangerous customer.”

I don’t know, that sounds like a massage to me.
The cleaner-client symbiosis, in many ways, mirror business relationships in the human world. For example, if we read reviews before watching a film or ordering a product online, prospective client fishes “watch the performances of cleaners before deciding whether to let a particular cleaner inspect them”, mucus-nipping cleaners are shunned, and cleaners do a better job when they are being watched.

“If a new client, who has no history with the cleaner, is cheated, he or she simply swims away. But a resident client who has built up a relationship of trust with the cleaner behaves as if having been insulted: he chases the cleaner around.”

Cheats get punished.
This social system is highly complex and “encompasses long-term relationships built on trust, crime and punishment, choosiness, audience awareness, reputation, and brownnosing.”
Guess what, there are also con artists in the fish world—fishes that pretend to be cleanerfishes, and when the client least expects it, the impostor takes a bite of fin and dashes for cover.
I can no longer look at fishes the same way again.