I need an emergency stock for seafood gumbo.

Why not buy an extra pound or so of shrimp for the shells, freezing the meat for later?

And I don't have a better suggestion.

How much stock do you need? But yes, the shells from a pound of shrimp simmered for 30+ minutes will be a vast improvement over water.

The seafood stock i was simmering today ended up very bitter. i think it was the lemons.

I wasnt cooking. They said it was in the recipe

That kitchen basics seafood stock is pretty good. Don't add lemons

Do they have gumbo crabs you can throw in to simmer?

Or just buy a half-pound or so of small shrimp and throw them all, not just the shells, in your stock pot. That shouldn't cost much.

I've used a few can of crab meat and some bottled clam juice. Works well IMO. I get no complaints.

HonDashi

It's freeze dried Dashi broth. Any respectable Asian food market will have it.

I slip a tablespoon in anything I cook with seafood. Brilliant stuff.

use chicken stock...

Trust me, it will add flavor