Shark ate someone

Question

Bava Kama 5:7 says

אֶחָד שׁוֹר וְאֶחָד כָּל בְּהֵמָה לִנְפִילַת הַבּוֹר, וּלְהַפְרָשַׁת הַר סִינַי, וּלְתַשְׁלוּמֵי כֶפֶל, וְלַהֲשָׁבַת אֲבֵדָה, לִפְרִיקָה, לַחֲסִימָה, לְכִלְאַיִם, וּלְשַׁבָּת. וְכֵן חַיָּה וָעוֹף כַּיּוֹצֵא בָהֶן. אִם כֵּן, לָמָּה נֶאֱמַר שׁוֹר אוֹ חֲמוֹר. אֶלָּא שֶׁדִּבֵּר הַכָּתוּב בַּהֹוֶה: ‏

Bulls or any other kind of domestic animal are equivalent for the purpose of payment for falling into a pit, the prohibition to go on Har Sinai during Matan Torah, paying double for a thief, returning a lost object, the requirement to unload a fallen animal, the prohibition on muzzling during work, kilayim, and working on Shabbos. And wild animals and birds are also the same. Why does it say "a bull or a donkey"? Because the Torah speaks about the normal case.

(Rashi says something similar about damage caused by an animal on Mishpatim 21:28 and the note on Sefaria says his source is the same Gemara, but I can't find it.)

Some of these halachos apply to all objects, living or not, while some are specific to animals. Do the animal halachos apply to fish?

Examples:

• If a shark eats someone, do we apply the normal rules of nezikin from a bull?
• At some aquariums they have an electric eel tank with a sensor that lights up and tells you how much electricity the eel is producing. My understanding is that the electricity from the eel directly powers the lights. Can you use this on Shabbos?
• If you hook it up to a food preparation machine with the proper parameters (גידולי קרקע etc.), do you have to set up some kind of contraption that lets the eel eat the same kind of food while it powers the machine?

Answer 1

Tosafot Shabbat 55a suggest that the rule forbidding working one’s animals on shabbat would apply to fish as well.

They think that this could be derived from a gezeira shavah linking shabbat to the prohibition of cross-breeding (which the gemara in Bava Kamma 55a definitively rules applies to fish).

Then, say Tosafot, we can learn from shabbat to other areas, such as the prohibition of attaching two different animals to the same vehicle.

(Tosafot also present a different approach, in which the prohibition of cross-breeding and working with different animals would apply to fish, but not necessarily shabbat or other areas.)

Answer 2

In terms of a shark, I'm pretty sure it'd fall under a case of wild animals ALWAYS being considered forewarned. The mishnah in Bava Kamma 15b addresses this, stating:

הזאב והארי והדוב והנמר והברדלס והנחש הרי אלו מועדין רבי אלעזר אומר בזמן שהן בני תרבות אינן מועדין והנחש מועד לעולם

The wolf; the lion; the bear; the leopard; the bardelas, and the snake. These are considered forewarned even if they had never previously caused damage. Rabbi Elazar says: When these animals are domesticated they are not considered forewarned. But the snake is always considered forewarned.

There's a machlokes Rashi vs Tosfos there:

Rashi says these animals are all considered forewarned in terms of biting or any other way it damages

Tosfos says, these animals are ONLY considered forewarned in their usual nature to damage (ex: a wolf tearing apart an animal) but a damaging act that's not in an animals normal nature (ex: a wolf rollerskating into a bed of roses) is not considered forewarned.

Based off Rashi & Tosfos, it would appear that if eating someone or injuring them via biting is in the shark's nature a person would be fully liable.

(for more in depth and some solid lomdus, see here)