Mmm, I see your point. I do not think a general rule fits here. Your example looks fine to me. If you envisage these words describing a stuffed goldfish in a museum, they work quite well. Keeping Fred in the present tense carries a connotation of effection, in my view. From a mathematical grammatical approach, it's also fine. Check this:
Considering that he played cards for a living, Fred is not that good at poker.
I think your concern is with Fred being dead and not with the past-tense/present-tense issue.