Translation:Even the fish are sick but I am fine.
My first thought as well - this definitely has the characteristics of a fine saying :-)
I have 2 questions Why not balığı if it is the fish and why the fish if it is lar
1) "balığı" is accusative case, so it's only for direct objects (when the fish is being eaten, found, caught, etc). But in this case, it is the subject of the sentence, so it remains in nominative case. In other words, nothing is happening to the fish, we're just describing them as sick.
2) And as for the plural, balık and balıklar are both fine in Turkish, but in English grammar, we usually say "fish" for either singular or plural. The word "fishes" is only for very specific contexts when we're talking about several species (ex. "Catalogue/Catalog of fishes") or when we want to sound like a mobster ("sleep with the fishes") ;-)