Today, I feel most (if not all) people can agree that red meat is unhealthy. Fish, though, it touted as being a wonder-food, is something you "can't get enough of." Sure, the nutritional profile isn't horrible — but there's more to it than just macronutrients.
When considering something for consumption, it's truly important to consider the resources, suffering, and environmental toxins involved (especially when it comes to fish).
The resources involved in fish consumption, primarily fish trawling, are astronomical. When we support fish trawling practices, we inherently support meaningless deaths, harm to natural ecosystems, destruction of the environment, and more — so much so that it's expected we will be living in a world of fish-less oceans by the year 2050. For every plate of sushi you consume, you also inherently kill off five feet's worth of sushi. The by-catch associated with this practice includes many species found on the endangered list, and many we say we 'love'; sea turtles, sharks, and sea horses are among the many species killed off by the thousands unnecessarily each and every year. Earlier this year, the Great Barrier Reef, a 25-million year old ecosystem, was pronounced dead. This in and of itself is a crazy and thought-provoking fact; we have single-handedly killed off an entire ecosystem that has survived for millions of years.
The common notion that fish do not feel pain is absolutely incorrect; they feel it just as much as we do, regardless of how similar and different we look. Fish are not vegetables, they are living creatures who have the ability to suffer. This unaddressed suffering is what makes the fishing industry so cruel. Fish are often left to gasp for breath and slowly die for up to ten minutes. Does slowly suffocating sound painless to you? When fish are brought up through nets (along with the aforementioned by-catch), something called compression occurs. As the net is lifted out of the water, the weight of the creatures on the top presses down on those lower near the bottom. As they are continually pulled up, this pressure can cause organs to come out from the mouth, bleeding from the eyes, and more.
Last but not least, there are the environmental toxins to consider in the consumption of fish. If you could care less about the environment and support of animal suffering, this area of concern is for you. The toxins in your food affect you.