Hello vilallva11,
These locks are there "by design". It means that this level of locking is expected and required. No way how to change it for FOR UPDATE clause. There is no DB/instance parameter to change it (trust IBM in this :-)), but you can try to rewrite the logic. It depends on the level of isolation you require.
Check combination of FOR READ ONLY and the USE AND KEEP UPDATE LOCKS together, isolation-clause and maybe WAIT FOR OUTCOME, but all options will need the change of the logic.
I hope it helps.
Regards
Ondrej