Bony fish

Bony fish vary fantastically in shape, color, size, distribution and diet. There are tens of thousands of species and that provides an amazing amount for Blizzard to draw from. Here's some of the best guess identifications I can come up with from my searching and my Reef Set of books or my Audubon Society Field Guide to...everything. Vashj'ir was an amazing addition, both in content, scope, story and new mechanics. I have really enjoyed moving around and exploring the reefs and other underwater ecosystems. Here's some of the cool fish hanging out around Azeroth.

Groupers

The Goliath Grouper (Epinephelus itajara) is the largest of the grouper family. They can grow up to 8ft long and 1000lbs.

p.s. groupers are yummy.

Moorish Idol

The Moorish Idol (Zanclus canescens) is a Pacific reef fish. Socially they congregate in schools, as is well demonstrated in-game.

Pufferfish

Pufferfish are found worldwide and range in size from a quarter to the size of a basketball. When spooked they inflate themselves with water (ingesting it into their very elastic stomach), making them larger and pointy and so, less likely to be eaten. There are more than 120 species of pufferfish worldwide. Most are found in tropical and subtropical ocean waters, but some species live in brackish and even fresh water. Almost all pufferfish contain tetrodotoxin, a substance that makes them foul tasting and often lethal to fish. To humans, tetrodotoxin is deadly, up to 1,200 times more poisonous than cyanide.
If they were ever made into hunter's pets, they could have a poison as their special ability... though... they are only deadly when eaten, so maybe it's when they are killed, it automatically kills what just killed them. So you could stand back, let the boss wail on him, and just wait for the puffer pet to die. Problem solved. Best taking pet ever. He may not be very happy about the arrangement, though.

Pirahna

I've a feeling the frenzies are supposed to be piranhas.
Rawr, I'm a piranha, I'm not as aggressive as I've been portrayed to be and some brother species of mine are even vegetarian. But, rawr, I'm so scary they'll make terrible horror movies about me. #shelvemewithSharktopus.

Couple of happy, little gold fish...except one is green.

New MoP skins are awesome, tattoo worthy.

Throw a flailing carp back into the water!

Goldfish (Carassius auratus auratus)

Meh... Koi, goldfish, It's all carp to me. I'll just group them together.
It's not like they are using them as a new sentient race in the new expansion or anything.
They are also one of the earliest fish to be domesticated...if you can domesticate a fish. I don't see them hauling my goods to market or herding sheep down the side of a mountain; that's all I'm sayin'.

Pearlfin

One of the new MoP races. They seem to be based off of Koi or Carp.

Remora (Remora remora)

Remoras use a modified dorsal fin as a "sucker" pad to cling to larger fish (like sharks) and sea turtles. The model in game is an excellent representation of these fish.

I'm not sure what these are...

Clownfish

A cute little reef fish that, by repeatedly swimming through the tentacles of the anemones can develop an immunity to the stinging cells and so live in relative safety among an animal that would eat lesser fish.

Blueheaded Wrasse (Thalassoma bifasciatum)

The males have the blue heads and the females are another color entirely. If the dominant male of the group dies then one of the females can change colors/genders and become male. (proving that you boys are replacable and women are strong and can do anything. So, when someone says the old, "if I were the last guy alive..." line you can just say "I'd kill you and then become the male progenator of a better, more peaceful species. Ha ha, I kid, I kid.)

Fairy Basslet (Gramma loreto)

They are from the West Atlantic and the Caribbean and only grow about 3 inches long.

Blue Tang (Paracanthurus hepatus)

A surgeonfish usually found in the tropical Pacific Ocean.

Frogfish or Toadfish

in this picture
Clown frogfishes (Antennarius maculatus).

Sea Horse, great mount!