Species such as the jackknife fish high-hat and some angelfishes have dark lines that run through the eyes. Some deep sea fish like the primitive jawless fish known as hagfish and lampreys gather round a corpse with surprising speed and eat it by burrowing into the animal and eating it from the inside out. But fishing there, especially bottom trawling, causes profound, lasting damage to fishes and life on the seafloor, such as deep-sea corals, these experts say. You wouldn’t want to bump into any of these fish while snorkelling on holiday. The swimmers and surfers are surely thankful for that. Once the boat arrives on site, a number of techniques can be used to fish.