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Juli’s Fish ID 101!

Fish ID with Juli!

Written by Juli Cole, 20 February 2024.

My training in university was as a field biologist, primarily interested in birds and reptiles, though frankly, anything moving in the grass? I wanted to find it and see it. As part of my skillset, I learned how to find an animal 20m up a conifer through a pair of binoculars, and in a blink of an eye, as that is about all the time one gets, identify it as either a Ruby Crowned Kinglet or Red Breasted Nuthatch (types of birds).  It was a constant hunt for shy animals who were fleeing the scene as soon as they caught sight of you.

Fast forward some years later, and I am in the underwater world. What a huge difference! There is life everywhere – an overabundance, big and small! And many are not shy or hard to see. My first experience with scuba diving was overwhelming – there was too much to take in. And I wanted to see everything, all at once and not miss it, who knows if I would ever see that fish again? I was swimming everywhere trying to see everything. My early GoPro videos reflect this – they are abominable to watch. With some more experience and study, I have learned a few things that have helped me calm down, somewhat. I have learned enough to tell the difference between an angelfish and a damselfish, a hawkfish and a goatfish, a grouper and a pufferfish, and if all else fails, I just call it a wrasse as they make up 600 species throughout the tropical regions. I can at least do better now than to say to the divemaster “I saw this fish next to a piece of coral – Do you know what it is?”

One would think the first ID marker would be the color, and though it does help, actually that is of lesser concern. Remember colors will change with depth. The first thing to identify is body shape – is it circular, square, blobby, typical fish shape, boxy, elongate?

The next part is to look at are the fins and tail. How are the fins arranged – two on each side and one top and bottom, or are they minimized and fused, stretched along the length of the body? The tail varies a lot and is really helpful to identify even between fish of the same family. They can be the typical triangle shape, split triangle, webbed, split webbed, pointed, flattened or elongated and elaborate.  

Some FIN variations on the body:

 Some TAIL variations:


Third would be markings/patterns: stripes- horizontal, vertical, diagonal, full body or only in certain parts; spots – polka dot like, large irregular, all over or only in one area; line patterns – wavy, close together, maze like, far apart. Then lastly are markings such as special dots on the tail or a band across the eye.

(Key to fish examples above Left to Right top row: Longfin Bannerfish, Bartail Goatfish, Spotted Boxfish, Panda Butterfly fish, Star Puffer. Left to Right bottom row: Comet, Striped Sweetlips, Clown Trigger, Black Saddled Toby, Two-Eyed Coralfish)

Okay now that I have completely overwhelmed you! Let’s talk about where the fish are found and what they are doing as this will also help to figure out what the fish is. And let me say I am no marine biologist! What I share here are my own limited observations. On the reef are going to be a lot of grazers and cleaners – for instance bigger pelagic fish such as mantas and sharks will come to these reefs to get cleaned, but they are not hanging out there. These reef fish are typically going to be foraging around, will be smaller (compared to say a barracuda), staying near their crevices so they can dart in when endangered. There are carnivores but small ones mostly feed on invertebrates. A healthy reef will also support a few larger predators such as groupers, lionfish and moray eels to help balance things out.

In the sandy areas will be many that actually live in the sand and use it as camouflage such as soles, gobies, jawfish, stingrays and so on. The ones floating above the sand are the brave ones who have protection. They are either pelagic and in schools (safety in numbers) or are the larger predators who can risk exposure such as sharks and trevallies. You might see schools of anchovies for instance out here above the sand but not typically on the reef – likewise a butterfly fish is not going to be out here but staying close to the reef.

Then there are those rocky, sandy areas that are not quite the coral covered reefs but are not the flat desert-like scrapes of sand. This is where you find the lie-in-wait predators like stonefish and crocodile fish, and moray eels. It’s kind of a badland of the reef and actually an exciting area to see unusual creatures. There are some smaller fish here such as damsel fish. Many night time fish like big-eyes, squirrel fish and so on are hanging out in small dark cave like areas during the day.

Having some understanding then of what fish behavior is like can also help you to figure out where to find that special fish you saw in a photo and would love to snap a selfie with. Understanding what the underwater terrain is like and how your special friend lives in it will greatly increase your chances of finding it. I am so excited to keep learning and understanding about our little part of the oceanic world here. I have spent years observing life above ground, but I feel there is so much more to see under the waves!

Some good references for starting out:

A cheap and easy way to start out are plastic cards, such as these made by PSI, found on Shopee or the like. They are pretty specific to our region and will help you at least start identifying major reef fish:

1. There are several online resources: – excellent chart of what features to look for and fish behavior – this one has photos and information but its backwards -have to know the fish you are looking for first

2. There are several online resources: – excellent chart of what features to look for and fish behavior – this one has photos and information but its backwards -have to know the fish you are looking for first

3. If you are willing to get serious and invest some money, this book is really good. There is also an e-book version that is easier to transport but not as easy to cruise through the photos. Currently Kinokuniya is listing it at RM265. I like it for the identification help at the beginning, the pictures are really nice and it is clear what to look for in the identification process. I found the e-book on this website   But this place seems pricey for an e-book so I am sure there must be other websites offering it (on US Amazon the physical book is listed at $32USD)  

Now that you are all equipped, go for a dive trip with Flow and start spotting out fishes! Double the fun by making it a challenge between you and your buddy! I hope that this little nugget is going to enrich your dives even more!

*Comet photo courtesy of; all other photos belonging to Anthony and Juli Cole

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