Obtained all fish. achievement in Story of Seasons: A Wonderful Life

This one takes some RNG but overall isn't that bad. There are 15 fish you will need to catch, and with each rod upgrade you will be able to catch more fish. Since you have to catch 500 fish and be in Year 3 in order to unlock the Golden Rod, you will undoubtedly catch all of the common fish on the way, but when you get the Golden Rod, you will unlock 4 more fish which will be much rarer than the rest. Here's a list of all of the fish and their locations just to make sure you don't miss any.

Fishing Rod:
Masu - Upper River
Wakasagi - Lower River/ Goddess Pond
Bucketmouth Bass - Lower stream/ Turtle Pond
Scad - Ocean

Copper Fishing Rod:
Spotted Char - Upper River
Amur Catfish - Turtle Pond
Calamari - Ocean

Silver Fishing Rod:
Stringfish - Upper River/ Turtle Pond
Rainbow Trout - Lower stream/ Goddess Pond
Ahi - Ocean
Red Seabream - Ocean

Golden Fishing Rod:
King Masu - Upper River
Unagi - Lower River
Bonytongue - Turtle Pond/ Goddess Pond
Langouste - Ocean