DREDGE

Again, the main idea of the game is fishing for profit and Pursuits. If you aren't giving the fish away as a sacrifice, to feed a hooded figure or for Bait, then chances are you will be able to sell the fish to the Fishmonger or Traveling Merchant. Sell $2500 worth of fish (I assume this means anything you catch, including crabs, lobsters, jellyfish, octopus, squid and all the rest non-fish in the game as well) from catching with your Rods, Nets, Crab Pots or Atrophy ability and you will have this trophy.