renewable-resources/data/minecraft/loot_table/gameplay/fishing.json

{
  "type": "minecraft:fishing",
  "pools": [
    {
      "rolls": 1,
      "entries": [
        {
          "type": "minecraft:loot_table",
          "value": "minecraft:gameplay/fishing/fish",
          "weight": 60
        },
        {
          "type": "minecraft:loot_table",
          "value": "minecraft:gameplay/fishing/junk",
          "weight": 25
        },
        {
          "type": "minecraft:loot_table",
          "value": "minecraft:gameplay/fishing/treasure",
          "weight": 15
        }
      ]
    }
  ]
}