Discretion
‘Vendors Of Fruits And Clothing…May Sell In Private’
(Mo’ed Katan 13b)
The Mishnha states that professional animal trappers may trap a large number of animals on Chol HaMo’ed to sell for the festival. However, while a non-professional may perform labor on Chol HaMo’ed in public, a professional must perform his work out of public view. The Magen Avraham (Orach Chayim 533:9) explains that he must do so because the large quantities with which he is dealing may cause some people to think he is conducting business for after the festival.
Out Of Public View
The Mishnah states a similar halacha with regards to a merchant selling his wares on Chol HaMo’ed. Even though he may sell items on Chol HaMo’ed that are needed for Yom Tov, he must conduct his business in a discreet manner, e.g., at a remote location and out of public view. The Gemara also states that if a businessman’s storefront faces the street, he may not leave the door open in the usual manner because that would attract too much attention (and there is a concern that observers will think he is selling items for post-festival use).
Perishables
The Gemara qualifies this halacha: A merchant selling perishable food (such as certain vegetables or fish) may sell his wares in public. Since the food cannot last until after the festival, it is obvious to an observer that it is being sold for festival consumption and there is no room for suspicion or confusion.
Based on this logic, the Rema (Orach Chayim 533:4-5), citing the Mordechai, rules that (in contrast to trappers of animals) a fisherman is permitted to fish in public on Chol HaMo’ed since people will understand that he plans to sell the fish for festival consumption.
The Magen Avraham (loc. cit. s.k. 10) disagrees, and maintains that a fisherman is forbidden to catch fish in public – even though it is apparent that he intends to sell the fish for the festival consumption.
Modern Refrigeration
In Zichron Shlomo (Hilchos Chol HaMo’ed Ch. 5, Note 26) it is asserted that professional fishing in public is forbidden in contemporary times even according to Rema. Since we now have the means of preserving fish (by freezing and canning), it is no longer evident that fish caught on Chol HaMo’ed will be consumed on the festival.
(Selling fish, baked goods, vegetables and other perishables in public, however, is still permitted today because these items, when sold at retail, are usually purchased for immediate use, not to freeze or can.)