From the sources
“וַיְבָ֧רֶךְ אֹתָ֛ם אֱלֹהִ֖ים לֵאמֹ֑ר פְּר֣וּ וּרְב֗וּ וּמִלְא֤וּ אֶת־הַמַּ֙יִם֙ בַּיַּמִּ֔ים וְהָע֖וֹף יִ֥רֶב בָּאָֽרֶץ׃” (ּBereishit א:כב)
“God blessed them, saying, “Be fruitful and multiply, fill the waters in the seas, and let the birds increase on the earth.”” (ּBereishit 1:22)
The birds and fish were given a special blessing that they be fruitful and multiply. This is also a blessing to people as the birds and fish fulfil human needs and desires (when they are eaten). So when man kills birds and fish for food, they are blessed to multiply so they will not die out through human consumption. Because of the sin of the snake, animals were not given the same blessing.
How to Eat it
This is a good week to serve fish and chicken rather than red meat. Here are some suggestions:
-a whole fish baked in the oven
-chicken stuffed with onion and etrog (left from Sukkot) and roasted in the oven.
-chicken soup (add bay leaves as an example of a “non-fruit” edible portion from a tree)
Alternatively, you could have a vegetarian Shabbat – see below concerning the fact that Adam HaRishon was not allowed to eat meat.