You may use present tense to describe something in the past which is still currently true. For example, "My cat catches lots of mice." This refers to the past (my cat, in the past, has caught lots of mice). However, I expect this should continue. My cat will probably continue catching mice. Therefore, I use "catches".
If my cat is very old and no longer catches mice, I would say "caught".
"When my cat was young, he caught lots of mice."