Tuna vs. Chicken
Yes, but not because of that flawed logic. Despite it’s nickname, tuna is nothing like chicken. It comes in several different varieties, but it tends to be much larger and more carnivorous (not that chickens are natural vegetarians, but they tend to be pretty low on the food chain, whereas tuna rank high).
Like most fish, tuna is an excellent source of protein, omega-3 fats, selenium, and various B vitamins. Most of these are nutrients we can’t get from other sources (at least not in the quantities available in fish), which means tuna can absolutely be included as part of a nutrient-dense Paleo lifestyle.
Farmed vs. Wild-Caught
Much like terrestrial meat, most fish are currently raised in farms, which can include small pens, inferior fish pellets for food, and doses of antibiotics and hormones to keep them from getting sick in their filthy pens. The good news is that even farmed tuna is fairly safe to eat.