NO it shouldn't. Fish is a collective noun. You use fish normally as the plural. There are specific cases to add "-es" but if you use it in English (and it's your native language, AND it's not for the reasons listed below)* I'm going to stare at you until you get paranoid.
*The Quick and Dirty Tip is that the plural of fish is fish, unless you’re writing about different species of fish, are a mobster, are quoting the Bible, or are trying to make a rhyme.
Both Pealim and Reverso offer transliteration. (About ten percent of the time Reverso is wrong however because it's computerised so it's based on the nikud). You can also find many of the words in a wiki... so just search the word in Hebrew with the word Hebrew... For instance: צבע Hebrew Another trick is to use lyricstranslate.com and Hebrewsongs.com they've got a lot of songs translated and transliterated into English from Hebrew. So just search Google with the Hebrew word like this: צבע site:lyricstranslate.com
Then you can see songs that have been transliterated with that word, see how they wrote it and then, listen to the song! (For me, it's really helpful to learn this way and helps me remember the vocab).
This is a great sentence for practice because it has two curve balls: ביצים is actually feminine though doesn't look it from the ים- ending and plural of fish in English is fish (to say "fishes" would be understood but no native speaker says it). I wonder if native Hebrew speakers sometimes say ביצות by accident. I'm guessing that ביצות sounds as odd as fishes.
Correct - ביצות sounds funny. I imagine it's a common temporary mistake of native Hebrew children learning to speak.
IIRC you know some stuff about Jewish tradition, so you might appreciate my little pun: when discussing food and cooking in Passover, I often say פסח הוא חג הביצות, which rhymes with the common phrase חג המצות. My listeners typically smile at this (-:
I'm not sure about that -- at the very least, I would say that British English does not follow this usage consistently. More to the point: is there anything in the Hebrew sentence that indicates all the fish(es) are of the same species? We might have a mixture of herring, trout and mackerel?