What does Rabban Shimon Ben Gamaliel mean?

Question

In beitza (3:1):

אֵין צָדִין דָּגִים מִן הַבֵּיבָרִין בְּיוֹם טוֹב, וְאֵין נוֹתְנִין לִפְנֵיהֶם מְזוֹנוֹת. אֲבָל צָדִין חַיָּה וָעוֹף מִן הַבֵּיבָרִין, וְנוֹתְנִין לִפְנֵיהֶם מְזוֹנוֹת. רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל אוֹמֵר, לֹא כָל הַבֵּיבָרִין שָׁוִין. זֶה הַכְּלָל, כָּל הַמְחֻסָּר צִידָה אָסוּר, וְשֶׁאֵינוֹ מְחֻסָּר צִידָה מֻתָּר:

One may not catch fish from a fishpond on Yom Tov nor give them food, But one may catch game or fowl from animal enclosures and one may put food before them. Rabban Shimon ben Gamaliel says: not all enclosures are alike. This is the general rule: anything that still needs to be trapped is forbidden but anything that need not be trapped is permitted.

What does Rabban Shimon Ben Gamaliel mean?

1. Is he differentiating between fishponds (that we are prohibited from fishing) and animal enclosures (which we may hunt), and then bring the general rule to show the difference between fish and fowl, and he agrees with tana Kama, and both agree with the general rule?

Or:
2) He says that we are allowed to fish from some fishponds, but not others, and/ or we are allowed to hunt from some game and fowl enclosures, but not all. And then Rabban Shimon Ben Gamliel finishes his view, and the tana Kama brings the general rule, to show the difference between fish and fowl. And Rabban shim’on Ben Gamliel is arguing on the tana Kama, and the tana kama brings the general rule?

Or (related but slightly different):
3) He says that we are allowed to fish from some fishponds, but not others, and/ or we are allowed to hunt from some game and fowl enclosures, but not all. And then Rabban Shimon Ben Gamaliel brings the general rule to show which enclosures one is permitted to hunt from, and which one is prohibited to hunt from. And he argues with the Tana Kama, and brings the general rule?

Kehati brings a view that seems like it makes sense with the second or third possibilities, but he starts it with “Yeish Omrim”, which seems to imply that others go by the first possibility.

Answer 1

The Gemara there says that Rabban Shimon ben Gamliel is not disagreeing, but adding to the Tanna Kamma.

It seems that the Mishnah says:

1. One may not trap or feed fish in a pond, because they require catching and can find food on their own.
2. One may trap and feed animals in an enclosure, because they do not require catching and cannot find food on their own. To this Rabban Gamliel qualifies that not all animal enclosures meet these criteria.
3. The Mishnah then says the general rule.

In other words, the difference between fish ponds and animal enclosures is not essential, but examples of the norm for those, as Rabban Gamliel points out. Based on his explanation (which is the halacha), we see the general rule is the halacha.

Thus Rambam says Rest on Holidays 2:7:

דָּגִים שֶׁבְּבֵיבָרִין גְּדוֹלִים וְכֵן חַיָּה וָעוֹף שֶׁבְּבֵיבָרִין גְּדוֹלִים כָּל שֶׁהוּא מְחֻסַּר צִידָה עַד שֶׁאוֹמְרִים הָבֵא מְצוּדָה וּנְצוּדֶנּוּ הֲרֵי זֶה מֻקְצֶה וְאֵין צָדִין אוֹתָן בְּיוֹם טוֹב וְאִם צָד לֹא יֹאכְלוֹ. וְכָל שֶׁאֵינוֹ צָרִיךְ מְצוּדָה הֲרֵי זֶה מוּכָן וְצָדִין אוֹתוֹ בְּיוֹם טוֹב וְאוֹכְלִין אוֹתוֹ. וְכֵן חַיָּה שֶׁקִּנְּנָה בְּפַרְדֵּס הַסָּמוּךְ לָעִיר יְלָדֶיהָ כְּשֶׁהֵן קְטַנִּים שֶׁאֵינָן צְרִיכִין צִידָה אֵינָם צְרִיכִים זִמּוּן מִפְּנֵי שֶׁדַּעְתּוֹ עֲלֵיהֶן:

7 [Regarding] fish that are in large ponds, and likewise animals and fowl that are in large corrals: All that lack trapping - to the point that [people] say, "Bring a trap and we will trap it" - are surely muktseh; so we may not trap them on a holiday. And if one did trap [it] - he may not eat it. But anything that does not require trapping is surely [considered to be] prepared; so we may trap them on a holiday and eat them. And likewise [in a case of] a wild animal that holed up in an orchard near a city: Its young - while they are [still] little, such that they do not require trapping [to slaughter them] - do not require setting aside, since he had his mind on them (to eat them on the holiday).