bedrock-samples/behavior_pack/spawn_rules/salmon.json

{
  "format_version": "1.8.0",
  "minecraft:spawn_rules": {
    "description": {
      "identifier": "minecraft:salmon",
      "population_control": "water_animal"
    },
    "conditions": [
      {
        "minecraft:density_limit": {
          "surface":10
        },
        "minecraft:spawns_on_surface": {},
        "minecraft:spawns_underwater": {},

        "minecraft:distance_filter": {
          "min": 12,
          "max": 32
        },
        "minecraft:weight": {
          "default": 26
        },
        "minecraft:height_filter": {
          "min": 0,
          "max": 64
        },
        "minecraft:herd": {
          "min_size":3,
          "max_size":5
        },

        "minecraft:biome_filter": [
          {"test": "has_biome_tag", "operator":"==", "value": "ocean"},
          {"test": "has_biome_tag", "operator":"!=", "value": "warm"}
        ]
      },
      {
        "minecraft:density_limit": {
          "surface":4
        },
        "minecraft:spawns_on_surface": {},
        "minecraft:spawns_underwater": {},

        "minecraft:distance_filter": {
          "min": 12,
          "max": 32
        },
        "minecraft:weight": {
          "default": 16
        },
        "minecraft:height_filter": {
          "min": 50,
          "max": 64
        },
        "minecraft:herd": {
          "min_size":3,
          "max_size":5
        },
    
        "minecraft:biome_filter": [
          {"test": "has_biome_tag", "operator":"==", "value": "river"}
        ]
      }
    ]
  }
}