Something Fishy

I can't make do with sturgeon any more:
If I can't get the lobster, watch your back,
There will be trouble. Get my gunny sack
Filled with crustaceans by the stroke of four
Or my claws will come out. And hold the door,
Don't let it hit me. What a lousy shack
You live in! In an octopus attack
We'll all be dead, and what's this poem for?

I write for all the lovers of snow crab,
The amateurs of seaside frolicking,
The soft-shelled workers learning how to sing,
The scientists abandoned in the lab.
I was disabled by a short left jab
Just as the jellyfish prepared its sting.