Q: Why is an exception made for eating fish on Fridays? Isn’t fish meat, too?
A: Biologically, yes; fish is also meat in that it is the flesh of an animal. However, one must be sensitive to the different senses in which one can use a term. Many people (Catholic and non-Catholic) do not use the term “meat” to refer to all animal flesh but only to the flesh of mammals and fowls. Most people, for example would not refer to the flesh of insects as “meat,” so right there we have an instance where “meat” does not denote everything which is the flesh of an animal (for insects are classified as belonging to the animal kingdom). Many people similarly exclude fish from the definition of the term.
Regardless of how broadly or narrowly the term “meat” is used, however, there are reasons why fish is not included in the Latin Rite’s abstinence. The reason meat was picked as the thing to abstain from is that in prior decades and centuries, meat (as opposed to fish) was a special sign of feasting and rejoicing since it couldn’t be had every day. Thus it was appropriate to deny oneself this sign of rejoicing as a gesture of sorrow for having offended God by one’s sins. However, fish (as opposed to meat) did not have this connotation. Fish was not a special sign of rejoicing the same way that meat was, as it was less expensive and did not require slaughtering one of the animals of the flock or herd.
A second reason, which is perhaps more relevant to those of us in the developed world today, for whom meat and fish are both equally available (and for whom fish may be even more expensive in the supermarket) is that fish is a symbol of Christ and by eating fish on Friday we are symbolically nourished by Christ while denying ourselves other forms of animal sustenance.
The most fundamental reason, however, is that in Latin and in the major European languages (French, Spanish, etc.), the word for “meat” never includes fish. Since the custom, for the Latin Rite of the Church, arose in Latin and Romance-language areas, it reflects this fact.
In fact, in English at the time arose, the same was true. The word “meat” at that point signified any and all food. To denote what we today call meat, the word “flesh” was used, and it too excluded fish. The system of classification that was used in English divided “meat” into “flesh, fish, and fowl.”
Since that time, the term “meat” has become restricted to what you find attached to the bones of mammals (flesh) and the bones of birds (fowl), and sometimes to what you find attached to the bones of fish, but that use is not universal even today.
In any event, the custom of eating fish but not flesh on Friday stems from this word usage in Western languages, in which there was a division between fish and what we today call “meat.”
In the Eastern Rites of the Catholic Church, the practice is different, and the Lenten fast includes an abstinence from all forms of animal products, including not only fish but also eggs, milk, cheese, butter, and condiments made with animal products (such as lard). However, while the Eastern Rite abstinence is stricter, it does not have the force of law, as it does in the Western Rite.
In the Latin Rite, where abstinence does have the force of law, it is a looser abstinence, giving exceptions for all animal products except meat itself (exclusive of fish) so people don’t have to wonder, “Was this made with lard?”, “Does this have cheese on it?”, etc. Only the animal flesh itself is to be abstained.