This writeup will cover some of the mechanics behind the waves in Salmon Run, and just what exactly changes when difficulty increases in Salmon Run.

The exact parameters can be seen here:

https://docs.google.com/spreadsheets/d/1kz18rgZxpKhz27Y1hmDQPiiKIIKny4OBB7V52Tsi12E/edit#gid=0

First up, general mechanics.

When a wave begins, the event type is determined first. What events can be experienced depends on your rank.

Apprentices cannot ever experience events. The waves will always be the normal kind.

Part Timers cannot ever experience Goldie Seeking, Cohock Charge, or Mothership. All other events are fair game. The chances for getting a specific event are as follows:

-9 in 12 chance of a normal wave.

-1 in 12 chance of Grillers, Fog, or Rush.

Go-Getters cannot ever experience Goldie Seeking or Mothership. All other events are fair game. The chances for getting a specific event are as follows:

-12 in 16 chance of a normal wave.

-1 in 16 chance of Grillers, Fog, Rush, or Cohock Charge.

For Overachievers and above, the chances for getting a specific event are as follows:

-18 in 24 chance of a normal wave.

-1 in 24 chance of Grillers, Fog, Goldie Seeking, Mothership, Rush, or Cohock Charge.

Next, depending on the event that was chosen, the tide type is then determined. The chances of getting a specific tide type are the same across all rankings.

If the event chosen is a normal wave, Fog, or Mothership:

-20% chance of being low tide.

-20% chance of being high tide.

-60% chance of being mid tide.

If the event chosen is Grillers, Goldie Seeking, or Rush:

-25% chance of being high tide.

-75% chance of being mid tide.

If the event chosen is Cohock Charge, then the tide will always be set to low tide.

During a normal wave, enemies will spawn every 30 frames during the first half of a wave. This decreases to every 20 frames once the second half of a wave is reached. Once the enemy limit is reached, the game will force spawns to stop until enough enemy slots are freed up for more enemies to spawn. When an enemy spawns, the game determines what type of lesser Salmond should spawn. Chum have a weight of 10. Small Fry have a weight of 1 (but they always spawn in groups of 3, unless they hit the enemy cap.) Cohocks are a special case. There's a limit as to how many can be on the map at once, and their spawn weight changes with the difficulty. The limit on how many Cohocks can be on the map at once increases as the difficulty rises as well. (More on this later.)

The maximum number of enemies that can be on a map at a time is 100 enemies. This applies to every wave type (Aside from low tide waves. More on this later.) When the cap is reached, no more lesser or Boss Salmonids will spawn until an enemy is killed.

(OUTDATED. The following sentence applies to version 3.1.0 or below only.) During a Mothership wave, there can only be a maximum of 10 crates on a map. And the active enemy cap decreases to 20.

Each Boss Salmonid has an equal chance of appearing. They always appear at set points during a wave. When and how many spawn depends on the difficulty.

Next up is difficulty mechanics, and how the waves change as difficulty increases. Difficulty is determined by the average rank of everyone in the lobby.

Normal Waves

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Maxmimum number of enemies that can be on the map during low tide is 100... Until you reach Overachiever to Profreshional 99, at which point, this decreases to 80. Past that point, it increases back to 100.

Quota increases.

-For wave 1, this ranges from 2 to 21.

-For wave 2, this ranges from 3 to 23.

-For wave 3, this ranges from 4 to 25.

Number of active enemies that can be in the first half of a wave increases.

-For wave 1, this ranges from 3 to 22.

-For wave 2, this ranges from 3 to 24.

-For wave 3, this ranges from 4 to 26.

Number of active enemies that can be in the second half of a wave increases.

-For wave 1, this ranges from 5 to 28.

-For wave 2, this ranges from 5 to 30.

-For wave 3, this ranges from 7 to 32.

Number of maximum Boss Salmonids that can be encountered in a wave increases.

-For wave 1, this ranges from 3 to 20.

-For wave 2, this ranges from 3 to 22.

-For wave 3, this ranges from 3 to 24.

Boss Salmonids will always spawn with lesser Salmonids. (Ranges from 1 to 3.) ...Until you reach Profreshional 100, at which point, this no longer occurs. (Because at this point, the map will start getting flooded with Salmonids of all kinds.)

Enemies will spawn in groups (Where they spawn from and such.) From Apprentice to Go-Getter, there will be 3 to 5 groups encountered per wave. Overachiever increases this number to 8. Then Profreshional 0 to 99 decreases this number to 6, and eventually the number increases back up to 8 once Hazard Level Max is reached.

-How many boss Salmonids at a time can be determined by dividing the number of maximum Boss Salmonids by the group count. (The variables in question in the document are mNormaGoldenIkuraNum, which is the maximum number of Boss Salmonids that can spawn in a wave, and mWaveChangeNum, which is the group count that was just discussed.)

Maxmimum number of Cohocks that can be on the map increases. (From 1 to 7.)

The spawn chance of Cohocks mostly remains static. (They have a spawn weight of 2 for most difficulties. Until you reach Overachiever, where they have a spawn weight of 5. Then decreases back to 2 once Profreshional 0 is reached. Once Hazard Level Max is reached, their spawn weight increases to 4.)

Grillers

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The higher the difficulty, the sooner you start seeing two Grillers at once. (The latest they can spawn is when 20 seconds are left in the wave. The earliest they can spawn is when 90 seconds are left in the wave.)

Griller movement speed increases. (From 1.3 to a maximum of 2.3.)

Fog (OUTDATED)

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The spawn rate of Goldies decrease. (Every 3rd boss Salmonid spawning will be a Goldie. Eventually, this rate decreases to every 5th boss Salmonid.)

See Normal Waves.

Rush

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Maxmimum number of enemies that can be on the map increases from 19 to 32.

Rush Chums spawn every 10 frames... Until you reach Profreshional 0 to 99. At which point, it decreases to 5. Once you get past Profreshional 100, it increases back to 10 frames and stays that way, even if Hazard Level Max is reached. (Goldies appear on every 20th spawn.)

Speed of Rush Chums increases. (2.2 to 3.5. Goldie movement speeds always stays the same.)

Cohock Charge

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Cannot be experienced until everyone is at least in Go-Getter.

See Normal Waves.

Goldie Seeking

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Cannot be experienced until everyone is at least in Overachiever.

Maxmimum number of Salmonids that spawn from wrong geysers that can be on the map increases. (16 to 48.)

No, you don't get any compensation buff to be able to get more golden eggs easier. Tough, deal with it.

Mothership (OUTDATED)

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Cannot be experienced until everyone is at least in Overachiever.

Mothership HP increases. (Minimum of 1800 HP to a maximum of 3500 HP.)

Crate spawn rate increases. (Every 110 frames to every 50 frames.)

The speed the Chinooks deliver the crates to their destinations increases. (0.9 to 2.)