| When a female koi is preparing to ovulate, all the other fish can smell it. The males start following and keeping close track of the situation least they miss out on the action. The smell also alerts the other females about what is going to happen and stimulates them into ovulation if they have well developed eggs. There is a benefit to synchronized mass spawning episodes because the egg/fry predators will be overwhelmed and the likelihood that an individual will survive is increased. A mass spawning episode in a confined pond is chaos. It is difficult to determine who is chasing who. When spawning is in progress, look to see which fish are trying to lift another fish out of the water - look for lifters and liftees. These are male and female respectively.
-steve hopkins |