The #1 reason gefilte fish is served at Shabbat dinner tables these days might be, in the words of Fiddler on the Roof, tradition! Originally, however, the dish that we currently call gefilte (a word meaning “stuffed”) was embraced for other reasons. Most notably: financial. Most families couldn’t afford to buy enough fish to feed their entire family, so they ground up fish and bones and mixed it with less-expensive grains.
Gefilte fish served religious purposes, too. Fish was often favored as a Sabbath appetizer because the Hebrew word for fish, dag, corresponds to the numerical value seven, which reflects the holiness of Shabbat, the seventh day. Gefilte fish also allowed people to eat fish on Shabbat without having to separate the bones–a process which is technically forbidden on Shabbat.
And gefilte fish was thought to have one added perk. According to the ancient sages, fish is an aphrodisiac. Thus, its presence on the Sabbath table could also encourage couples to “be fruitful and multiply.”