Hi, Sarah —

Thanks for the question.

A fish is not meat by definition.   It has been historically distinguished from other animals.

Fish on Fridays actually has more to do with the "fish" being the sign of the early Christians,
than with not eating meat on Friday.

Fridays during Lent, in a special way, draw focus to the holiness of Friday, the day Christ died on the Cross. By limiting our eating, and eating "fish", it helps us focus ourselves, spiritually.

Fasting has multiple principles, one of which is sacrifice, but note that fasting has to do with,
how much you eat, not what you eat.

We are required to abstain from meat on all the Fridays in Lent along with Ash Wednesday.
We are required to fast, as well as abstain, from meat only on Good Friday and Ash Wednesday.

That said: having a lobster dinner with all the fixings is not exactly fasting.

Abstinence also has many principles.   Like fasting, sacrifice can be one of them but it also serves the purpose of reminding us that there is something different about the day we are observing.
We live in a world of physical realities, and thus, things like meal preparation, or going out of your way to find a meal rather than the local burger joint at lunch time, help us to remember why we are doing so.

There is nothing more holy about fish than meat, other than what you said: It is protein, and it is a way of substituting the protein on a day of abstinence.

Hope this helps,

John DiMascio and Fr. Nick