The Tzemach Tzedek and the Shabbos Fish Boycott
When gentile merchants raised the price of fish because Jews always bought it for Shabbos, the Tzemach Tzedek ruled that a temporary boycott was proper, for the sake of the poor.
However, was that measure only for the birds, or can it be applied to fish as well? Mullet it over for a second, then read the rest. (I briefly discussed this issue last week.) The question was posed to the Tzemach Tzedek (the rishon). It seems that hundreds of years ago, the gentiles of that place knew that the Jews had the halibut of buying fish for Shabbos, and they cod raise the prices without suffering a drop-off in sales. When the prices increased dramatically, the Jews realized that something was fishy. Some were in favor of instituting a temporary ban on the purchase of fish for Shabbos to cause the price to sink.
Others, however, referred to the Gemara in Beitzah (16a) that the money one spends on Shabbos and yom tov is not deducted from one’s yearly allotment. So, they reasoned, what difference does it make if the fish is expensive? Since they are buying it for Shabbos, their money will be returned to them in one way or another through Divine intervention, and they will remain afloat.
The Tzemach Tzedek ruled that a boycott was in order. Just as Rabban Shimon ben Gamliel curtailed the offering of korbanos, we may temporarily curtail the mitzvah of oneg Shabbos. This would be true even if eating fish on Shabbos is a mitzvah d’Oraysa, as some argue (see the Shulchan Aruch HaRav). However, for halachah l’maaseh we hold that eating fish is just one manifestation of the mitzvah of oneg Shabbos. One can fulfill the biblical mitzvah of oneg Shabbos with other dishes as well. So a boycott is certainly in order to bring the price of fish down.
As to the argument that the money spent on Shabbos will be returned: The Tzemach Tzedek said that it is fine for people who have the money to lay out, but not for a poor person who does not have the money to spend now and will not be able to buy the fish, even though there is a guarantee that the money will be returned to him later. Since these poor people were floundering, a temporary ban on buying fish for Shabbos was proper.