Scientists have built a significant body of research that shows that fishes display all the features commonly associated with intelligence in mammals, and that they experience stress, fear and pain. These findings have significant ramifications for animal welfare legislation, an area from which fishes have been traditionally excluded. Our most detrimental interaction with fishes is through commercial fisheries and aquaculture, an industry that feeds billions of humans and employs millions more. We have invented a vast array of fishing methods that extract fishes from almost every region on the planet in an equally vast range of violent and painful ways. Fisheries managers regularly fail to prevent overfishing to ensure healthy populations of target species, have not adequately addressed the impacts on other marine species and the broader environment, nor prevented human rights abuses on board fishing vessels. Fish welfare has not been a consideration. Farmed fishes are under our control for their entire lives, and while there are welfare guidelines available, where these are applied, the goal is primarily to maximise production and reduce losses, rather than ensure good welfare. These industries are important to many of us; however, we need to change these systems to address both welfare and sustainability. For fisheries this means a reduction in the number of fishes killed, by addressing overfishing and wasteful capture methods, and reducing the length of time fishes suffer during capture. For aquaculture this means keeping fishes in more natural environments at lower densities, reducing transport and handling impacts, and choosing species that cope better with farming. Both sectors need to develop humane slaughtering practices. Fish behaviour and welfare experts will benefit from working with the people and systems that are driving more ethical and sustainable practices in fisheries and farming, to help initiate improvements that will benefit individual fishes and the broader marine environment, as well as the lives of those working in the industry. We must ensure that where we do need to farm and capture fishes it is done humanely, fairly and without unnecessary waste of trillions of lives. A simple way forward would be to reduce our reliance on fish as a primary source of protein, particularly in wealthy countries where alternatives abound.