Fish – Are all “fish” truly fish?

Not Every “Fish” is a Fish

Taxonomy is the science of labelling and classification. Throughout history, scientists have had their fair share of mistakes. Since the ocean is so vast, some animals have been misclassified.  The term “fish” has been misclassified for a very long time. This is because there was a lack of standardisation for the classification of animals in the past. 

What is a Fish?

lung fish
The lungfish can breathe through lungs as well as gills.

At first glance, it seems like a very silly question. I mean, a fish is simply an aquatic creature with gills and scales right? Well… not exactly. Fish are a very diverse group of animals. Here are some fish that don’t fall neatly into their classification.

Mudskippers can live on land as well as water
Tuna fish are warm-blooded
Hagfish don’t have scales like most fish

Therefore, the best definition we have for is this…

Most fish are cold-blooded vertebrates, with fins, wet scales and gills.

Some animals that aren’t actually fish:


sea jelly
Jellyfish aren’t fish because they don’t have any bones. They have a new name called sea jellies. 
Silverfish are insects, not fish. They are called silverfish because their abdomen are streamlined like a fish’s tail. 
sea star
Starfish aren’t fish either. Scientists have relabelled them as sea stars.

In conclusion, fish are a little tricky to classify. But if we keep to the general definition that fish are animals with scales and gills; it may be too simplistic. As your child learns how to classify animals, it is best to start with a clear definition so as to avoid future confusion.

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