I suppose it would have made more sense to have written this before explaining stickleback parental care, but it took me a while to get a reasonably good video of courtship behaviour.
Stickleback courtship has been studied since the 1930s, when Niko Tinbergen began investigating it. That is, the male’s role has been studied since then; it wasn’t til the 80s or so that people properly characterized female behaviour.
Here’s a quick overview: The males, as I’ve explained before, build nests. They also develop a red throat and belly, a bright blue iris, and, depending on the population, a blue body.
When a male spots a gravid female, he initiates courtship by either approaching her directly or zigzagging towards her. This zigzagging is pretty obvious in the video I’ve included below.
The female will respond with a “head-up”, a posture that shows off her egg-filled belly. The male may then nip at the female or swim below her and prick at her underside with his dorsal spines. (Interestingly, limnetic males do more zigzagging, while benthic males do more biting.) Then he’ll try to lead her back to the nest, following a meandering path. He pokes at the entrance to the nest with his snout, and then the female, assuming she’s still interested, will check out the nest too. If she decides to spawn, she swims into the nest and deposits her eggs, which takes about a minute. After she swims out the male swims through to fertilize them.
I made this video of a limnetic male courting a female in a jar (that’s how I get them to nest), which for obvious reasons can only show a few aspects of courtship behaviour. The nest is right in the middle of the frame (there are bits of plants around it).