Catfish of the genus Corydoras, for example, spawn immediately after heavy rain, the specific cues being an increase in water level and a decrease in temperature.
This can be a dangerous strategy, as if they wait too long, they may get trapped in small pockets of water, and die when the levels recede.Discus will breed when the temperature goes up and there is an overabundance of food such as mosquito larvae.
Many fish stock up on energy reserves to ensure they make it through this exhausting period that is very hard on their bodies, while others go without eating during the spawning process because they are so focused on their offspring.
In most cases, if these triggers were not present, male and female fish would not meet at the right stage and the number of offspring would be reduced.
Some fish, like salmon, spend almost their whole life muaturin in the ocean, then swim many miles up their ancestral rivers, to lay their eggs, commonly dying after spawning.