Mers are broken up in many different ways by many different variables.
Here is how they are broken up by the depths they usually reside at.
(NOTE: The glassback breed has been renamed the Glass Leera breed. We need more Leera's and fewer Backs. XD)
The different categories are Shallows, Open Ocean, Deep Ocean and Polar.
Shallows: Mers who like to live in warmer waters and closer to the surface and shore, usually in coves, bays, coral reefs and tropical shallows like the Caribbean.
Open Ocean: Mers who live generally where the sunlight reaches in the open ocean and near the shallows. They live a bit deeper then Shallow Mers. They don't go deeper then the sunlight though.
Deep Ocean: Mers who live like the open ocean mers but who can hunt and dive down into the dark depths deep down.
Polar: Mers who live in in arctic or antarctic waters.
Firebacks: Open Ocean
Glass Leera: Shallows
Pacific Leopardbacks: Deep Ocean
Atlantic Leopardbacks: Deep Ocean
Southern Tigerbacks: Shallows
Northern Tigerbacks: Open Ocean
Gold Midians: Shallows
Evening Midians: Open Ocean
Mariana Blacks: Deep Ocean
Emerald Leera: Open Ocean
Ebony Royals: Open Ocean
Arctic Whites: Deep Ocean
Northern Blues: Open Ocean
Stonebacks: Open Ocean
Southern Blues: Shallow
Wild Akoia: Shallow
Silver Zephree: Open Ocean
Smoke Zephree: Open Ocean