John Gamel asked:
The drive to procreate is one of the most powerful forces on earth. To assure procreation, nature offers as a "bribe" a certain amount of physical pleasure. This is easy to understand for those species who actually make physical contact during copulation, but fish remain a total mystery: how does ejecting one's eggs or sperm into a stream or the ocean bring an ecstatic experience?
We posed this question to Mark Bretha, Marine Biologist at Plymouth University...
Mark - The fundamental question here is whether fish are ever capable of experiencing pleasure at all, including at the spawning event when they release their gametes. One problem that we have is that we can't exactly go up to a fish and ask, ďhow was it for you darling?Ē And this is a general problem in understanding what feelings non-human animals might or might not experience.
One area that has been the subject of a large amount of research in fish is the experience, not of pleasure, but a pain. In an experiment with rainbow trout, we see an injection that wouldíve been painful to humans, they show behaviours like rubbing the affected area which went beyond a simple reflex response and that were also specific nerve fibres that responded to the injection. Therefore, fish might experience something akin to pain in humans.
As far as pleasure goes, there are some anecdotal evidence that when client fish interact with cleaner wrasse, they might enjoy the touch sensations of being cleaned.
In the case of spawning, we know about the hormonal control of the events but we don't yet know whether itís an ecstatic experience, altohugh itís perhaps nice to think that there's the possibility that cyclids can get their kicks and brill get a thrill from spawning.
Diana - Itís possible that there is some sort of neurological reward for fish when they reproduce, but we don't yet know if itís pleasurable or if it makes the, er, water move.
It must be some experience...
Not everything we do requires that we derive pleasure out of it. For example, not too many people get great pleasure out of breathing, yet we do so anyway. it can be hard to sometimes put a line between pleasure and some sort of biological instinct but we can look at some breeding practices and see that not all creatures find it "pleasurable".
Great points, qazwart; thanks. chris, Sun, 11th Dec 2011
It's probably hard wired (instinct) and pleasure does not come into it.
Q : What did one male grouper say to the other?