This saying is akin to something like “Better to be the head of a dog than the tail of a lion” in English.  While I don’t agree with the “don’t be too ambitious” slant of the saying at all, it’s still pretty cool.  Plus, there are the names of two fish in there, so hey… free vocab!

Note also that 頭, which is often pronounced あたま is, in this case, read かしら.

苦あれば楽あり

苦 has a variety of meanings, but all tend to fall into the area of bitterness/hardship/suffering.  あれば simply means “if exists” or “if (one) has.”  楽 is often used when describing music (e.g. 音楽) but also has connotations of fun, ease, or comfort.  All this taken together, the phrase really means something more like “if you struggle through bitter hardship, you will have ease.”

There’s a flavor (pardon the pun) to this that, in my opinion, isn’t quite there in either of the aforementioned English versions.  “Every cloud has a silver lining” seems to be too fairytale-ish and passive for me, and “no pain, no gain” doesn’t really talk about what the “pain” is.  I mean, you can hit yourself in the face with an ice pick repeatedly and cause pain, while experiencing no demonstrable “gain.”

A related phrase is 苦は楽の種 [くはらくのたね] or “bitterness is the seed of ease.”

This proverb really explains a lot about Japanese society.  Namely, that it’s best to keep your head down, toe the line, and not make waves, lest you be hammered back into your “place” by society.

The phrase is sometimes rendered with the character 釘 (nail/peg) instead of 杭 (peg/post).  From what I’ve been able to tell in my research, the use of 釘 is incorrect, but that doesn’t stop people from using it.