i found these sites today:
http://oceanwise.ca/seafood
http://www.goodfishguide.co.uk/
http://wwf.panda.org/what_we_do/how_we_w...od_guides/

it's really useful... it tells you which fish you can safely eat and which to avoid in terms of sustainability and environmental damage. It's also updated regularly with new recommendations as research continues.

Although some of it's recommendations aren't entirely helpful since you often don't know the method by which the fish are caught, it seems like a good guide to making your buying a bit more ethical, at least.

i found it while i was looking for something that apparently doesn't exist... actual numbers of how much meat / fish / other products is sustainable to eat for each person per month / year. If anyone's seen such a site, please let me know!!

Regarding eatable fish amounts, can't toxins also be a limiting factor?

I wish the supermarkets would just put stickers on things like they do nutritional information.

The New England Aquarium publishes recommended seafood choices, among other ways that they promote sustainability. If you live in New England, their list makes note of local species (therefore more likely to be fresher, and reducing fuel burned for transportation.)

http://www.neaq.org/conservation_and_res.../index.php

As for how much a person can eat sustainably... I think it isn't really relevant, because there are people that are going to eat seafood every day and people that are never going to eat seafood - what one person's 'share' would be if everyone ate equally is a question more valuable for determining the population the planet can support than figuring out what to eat for dinner.
It's very difficult, in any case, to eat in a way that contributes -more- to a sustainable food supply than by making informed seafood choices. I wouldn't encourage anybody to limit their seafood intake for that reason.

Sustainable seafood choices, by the by, are also often healthy seafood choices with regard to heavy metals - fast-growing fish populations that are relatively low on the food chain (Tilapia being a prime example) have less time to build up heavy metals in their bodies to transfer to you. Heavy metals are more of a concern with large, slow-growing predator fish - the rich flavors come with a price. Unfortunately, I don't have a list of heavy-metal risks by species at hand, but I have a feeling it's out there.

^^ yeah, that's true, but... i'd still like to make sure i didn't eat more than my fair share for the world. The figure would change as the human population rose, and i could adapt to that.

With fish, it seems like choosing sustainabilty is the most important choice, rather than a simple amount, but the story's a little different for meat products. I like meat, so i don't really want to cut it out completely, but the costs of farming meat really are horrendous. It'd be nice to know how much meat i could eat as a fair share (taking into account the production costs and what else could have been grown on that land.). Again, farming method would make a difference, but it'd be nice to have some ballpark figure, at least.