Tips for going eco-friendly: Go Grassfed: grass is a cow's natural diet, thus making healthier animals and tastier meat. Healthy animals, healthy people. Use CSA meat, support local community farmers and ranchers and reduce the carbon impact.
Go for oysters: Farmed is a great choice, not only is it healthy but good for the planet. Oysters will not grow if the water is not clean or if conditions are unsustainable, so unlike many fish farm practices, oyster farming is eco-friendly.
Pick the best shrimp? Wild is best and is the most eco-friendly option for shellfish. Farmed may have contaminants.
Other options: Sardines, sushi, fish and chicken (although conventional chicken farming is bad for people and even worse for the chickens). It is high in hormones , antibiotics and very high in saturated fat, almost as much as beef. Try exotics: There are lots of options here, emu, ostrich, bison, elk, deer, etc.