What do i need to do to get a 5kg barbel?

I've been at this one particular challenge for roughly 60 hours in game. I've tried all the spots on bear lake, copper and amber with every bait that has ever caught a barbel. I just need this challenge to complete them all and am having absolutely zero luck.

Any help would be appreciated as I've only 9 days left to complete this challenge that I've been going for for over 2 weeks.