so ian roberts says he sees it as almost his duty to farm fish. >> roberts: we farm everything we eatarmed. all our meats are farmed. the ocean is the last place where we hunted and gathered. the problem is there is seven billion of us now on this planet. and the oceans can't give us any more fish. we owe it to our oceans to make sure that we're providing an alternate to just capturing the last wild fish. >> gupta: marine harvest owns about 30 farms just like this one in british columbia. each farm is about the size of a couple football fields, built in calm ocean inlets where farmed salmon can thrive. >> roberts: here, i'll get you just to grab his tail there and see how he kicks. >> gupta: okay. ( laughter ) am i being hazed? is that what that was? >> roberts: that's exactly what it is. that's a nice looking fish. >> gupta: while these fish appear normal... you're free into the pen. ...the environment they live in is anything but normal. salmon, which are naturally white in color, get their pink color from eating shrimp and other creatures in the wild that have chemicals called caro