Channel 4 launched the app to highlight 'fish to eat' and 'fish to avoid', and to provide recipes.
However, iTunes has been flooded with complaints since its launch. One reviewer claimed the app took two to three minutes to load, another said it had taken "an age".
A third asked: "How can you release an app that doesn't even load. Rubbish!"
Once it had started working, the app was "really interesting and useful to all those concerned about the sustainability of our oceans," said another.
Free from iTunes, the app was developed in conjunction with Hugh Fearnley-Whittingstall, the Marine Conservation Society and Selfridges.