Excepting documents, this page provides info on various communication tools such as displays, flyers, websites, and audio-video media.

"A program of Monterey Bay Aquarium designed to raise consumer awareness about the importance of buying seafood from sustainable sources. We recommend which seafood to buy or avoid, helping consumers to become advocates for environmentally friendly seafood."

Have a look at their excellent site: http://www.mbayaq.org/cr/seafoodwatch.asp

Pocket-sized national guide (regional guides for the US also available)

Fish - A Consumer's Guide

One small thought is to take a look at WWF's Fish consumer's guide (tiny pocket guide you carry in your wallet to help you choose wisely when shopping it uses simple 3 categories: "fish to eat", "think twice" and "don't buy". I realise you are more focusing on zoos and aquaria but it may be of interest as a tool for the overall campaign

WWF Fish Guide

From WWF Switzerland, see also:
http://www.wwf.ch/de/tun/tipps_fur_den_alltag/
essenundtrinken/fisch/einkaufsfuhrerfisch/index.cfm