Gemara

(Rav Ashi citing Shmuel): If one takes a fish out of the sea on Shabbos, once an area the size of a Sela (a certain coin) dries up, he is liable.

R. Yosi ben R. Avin: This is if it dried between its fins.

(Rav Ashi): It need not become fully dry. It suffices if sticky strands exude when one touches it.

Shabbos 75a - (Mishnah): Slaughtering (is an Av Melachah).

Question: Why is one liable for slaughtering?

Answer #1 (Rav): He is liable for dying (the blood colors the skin).

Answer #2 (Shmuel): He is liable for killing.

Question: Does Rav holds that he is liable only for dying, but not for killing?!

Answer: He means, he is liable even for dying.

Rav: If I do not explain myself, later generations will mock my words (one is liable only if he desired the outcome). He wants the place of slaughter to be bloodstained, so people will see (that it was slaughtered today) and come to buy.

(Beraisa): If one hunts a Chilazon and presses it (to extract its blood), he is liable only once.

R. Yehudah is Mechayev twice;

R. Yehudah: Extracting the blood is included in Dash.

Chachamim: It is not.

(Rava): Chachamim hold that Dash applies only to Gidulei Karka (things that grow from the ground).

Rishonim

Rambam (Hilchos Shabbos 11:1): If one slaughters, he is liable. Anyone who kills any Behemah, Chayah, bird, fish or Sheretz, whether through Shechitah, Nechirah (other ways of killing it through the Simanim) or striking it, is liable. If one choked a live being until it died, this is a Toldah of Shechitah.

Question (Lechem Mishneh): Why does the Rambam rule like Shmuel against Rav? The Halachah follows Rav in Isurim!

Answer #1 (Lechem Mishneh): Rav's answer was very weak. Rav himself said 'If I do not explain myself, later generations will mock my words' and the answer he gave is flimsy.

Answer #2 (Chasam Sofer Shabbos 75a DH Rav): Rav holds that tanning applies to food, therefore also dying applies to food. The Rambam rules like Shmuel because we hold that tanning does not apply to food.

Answer #3 (Chacham Tzvi 92): The Rambam is Mechayev for dying water only if one cannot drink it, but dying does not apply to anything edible. Even Rav is Mechayev only because the blood is Asur to eat. Surely, all permit diluting red wine on Shabbos, even though this colors the water!

Answer #4 (Chasam Sofer Beitzah 26b DH Muktzeh): A Mishnah (Chulin 14a) says that one is Chayav Misah b'Yedei Shomayim for Shechitah. According to Shmuel this cannot be like Isi ben Yehudah, who says that there is one Melachah of Shabbos for which one is not killed. According to Rav this can be like Isi, for Shechitah is liable for dying and killing, so in any case one is Chayav Misah for one of the Melachos. R. Zeira rules unlike Isi, therefore the Rambam rules like Shmuel against Rav.

Hagahos Maimoniyos (1): The Yerushalmi says that causing bleeding is (liable for) killing.

Question (Tosfos R. Akiva Eiger Shabbos 14:1 (137)): The Rambam (Shabbos 8:7) says that wounding is liable for Dash (it extracts the blood). If so, why is Shechitah liable only for killing? Even if he has no use for the blood, one who wounds to damage is exempt only because it is Mekalkel (destructive). Shechitah is not Mekalkel! It is difficult to say that he discusses when less than a k'Grogeres of blood came out.

Merumei Sadeh (Yerushalmi Shabbos 7:2 DH Sham ha'Tzov'o): The Rambam is Mechayev for Netilas Neshamah only for killing. He must agree when all the blood from a limb was extracted, for it is like dead.

Rambam (ibid.): Therefore, if one took a fish out of a flask of water and left it until it died, he is liable for choking. Even if he left it until the size of a Sela dried up he is liable, for after this it cannot live.

Minchas Chinuch (32, Mosach ha'Shabbos 29): It need not die right away. As long as one caused that it will not live, he is liable for Netilas Neshamah. If so, one is liable even for making an animal Tereifah if there is no cure.

Tosfos (Chulin 29b DH Kegon): One is not liable for cutting one Siman (of Shechitah) on Shabbos, for this is not Tikun.

Note: This is if he intends for Shechitah. If he merely needs to kill the animal, e.g. for its hide, cutting either Siman will make it die.

Poskim

Shulchan Aruch (OC 316:8): If one wounds one of the eight Sheratzim listed in the Torah, even if the blood did not leave but was Nitzrar (gathered in one place and will not be reabsorbed), he is liable. One is not liable for wounding other Sheratzim unless the blood left.

Beis Yosef (DH u'Mah she'Chosav Rabeinu): The Ran says that one is liable for Netilas Neshamah. Regarding the eight, the skin can hold in the blood even if was displaced. Other Sheratzim have no skin, so one is exempt unless the blood left. The Rambam never obligates for other Sheratzim. This is difficult, for a Beraisa obligates.

Magen Avraham (15): Some say that wounding is liable for extracting, a Toldah of Dash. Even though Dash applies only Gidulei Karka, regarding this animals are considered Gidulei Karka. Some say that he is liable for dying. Most say that he is liable for Netilas Neshamah.

Mishnah Berurah (29): Even if only a drop of blood came out he is liable, for blood is the Nefesh, and he removed some of it in that place.

Mishnah Berurah (30): The Rambam and Ra'avad argue about whether one is liable for wounding a person or someone else's animal out of anger. In any case it is forbidden. One must be very careful not to strike any living being in a way that can draw blood. One may not scratch a Shechin (scab), for this can cause bleeding, which is wounding. Therefore, removing a tooth is a Melachah. Some exempt for this, for the wound is a Melachah she'Einah Tzerichah l'Gufah.

Mishnah Berurah (33): If one took fish from the sea he is liable for trapping. He is not liable for Netilas Neshamah unless he left them to dry.

Kaf ha'Chayim (62): If one hit his son for Chinuch and drew blood he is liable. This is not Chinuch, rather, madness.

Kaf ha'Chayim (63): L'Chatchilah one should not clean his teeth with a needle or scratch himself greatly lest he draw blood.