Chain your catches by catching the same species for Pokemon again and again in a row, without breaking your chain.
This results in receiving bonus EXP, guaranteed perfect IVs, and an increased chance of seeing a shiny Pokemon.
Your chain breaks if:
A wild Pokémon flees.
A Pokemon of a different species is caught (including one of the same evolutionary family).
You crash or exit the game.
View the Pixelmon wiki for detailed information:
NOTE: The perfect IVs gained from catching IVs has been changed and caps out at 3. See the table to the right.