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How to Identify Fishes

You go on a dive, or catch a fish and you want to find out what it is. How do you go about identifying it?

If you are experienced at identifying fish, it's usually quite easy to do; you'd probably have a good idea as to what family the fish is in and go to the relevant section of a good fish book, such as Smith's Sea Fishes, or for more common fish, a book such as Dennis King's excellent little Reef Fishes and Corals, Rudy Van Der Elst's Common Sea Fishes of Southern Africa or the Two Oceans book by Branch et. al. However, that's all very well and good for the experienced - others find it much more difficult to find the fish they are looking at in a book!

Most books have great illustrations of fish; some of them have helpful illustrations at the beginning of the book giving a generalised outline drawing for each fish family so you can then go to the relevant section in the book to further identify it. Others have illustrations of fishes throughout the text or at the back and you can always browse though those trying to recognise the fish you have seen (a slow method, but it works!).

Describing the fish you see to someone who is familiar with the fishes in the area will often result in a couple of pictures of fish being shown to you and you can then decide which of the two or three species you are looking at, and sometimes, straight off they'll say that's a ...... . It all depends on how good your description is and how well they know the fish you've seen!

It is always a lot easier if you take a photograph of the fish underwater; the memory is notoriously unreliable for remembering exact colour patterns and shapes in a fish, which are generally vital for identification. You can also make a quick sketch of the shape of the fish on a slate and make some notes on the colours next to the sketch if you don't have a camera. Also, get your buddy to notice the fish and make a mental note of it. (Arrange some signs you can use underwater for this. I usually find pointing at my eyes (look at), then at the fish (that) I want to remember and then pointing at my temple (remember) is fairly self explanatory!). If the two of you agree on the identification of the fish when you look it up, chances are you are probably right. On a diving holiday in the Red Sea last year, after a while the whole group cottoned on to this idea and dragged me over to remember this fish and that fish - it generally worked quite well, and resulted in me seeing even more species that I would otherwise have done! It also taught them a lot more about the fish, and resulted in a post dive flurry of activity flipping though the few fish books we had on board the boat, and more interesting log book entries as well. After about fifteen years of learning (mainly freshwater) fish species and their names, I am reasonably proficient at remembering details, but from time to time, you come across something unexpected, like when I saw my first Emperor (Family Lethrinidae) (also on that trip) - I thought I was seeing a Cichlid in the sea (something which does not happen as Cichlids are almost entirely restricted to freshwater, apart from a few species which venture into brackish water). I took a quick snapshot of the fish and looked it up to find I had been fooled by a superficial resemblance to some fishes I was familiar with by a fish I had not seen before - beware of that pitfall!

With an actual specimen, you can go about the more technical identification methods such as fin and scale counts and so on. At the back of Smith's Sea Fishes is a whole list of fin ray formulae; if you correctly count the dorsal and anal fin rays and spines, you can then use these to identify your specimen. A look at the entry for that species in the main body of the book will then confirm or refute this diagnosis (if it looks nothing like the fish you have, you have either counted wrongly or have a fish which is not in the fin formula key). Further instructions are given in the book. 

If you cannot identify a fish, and have a reasonable photograph of the fish or an actual specimen, you can send them to the JLB Smith Institute of Ichthyology and we will try our best to identify them for you.

Finally, there is no substitute for experience! The more fish you look at, the better you become at recognising them and spotting the differences between them. A good photograph makes identification of most fish relatively easy, but with some groups, actual specimens are necessary to be absolutely sure of the exact species you are looking at. Coming on Fish-Watch dives will give you some experience in identifying fishes and gives you a chance to ask us questions about the fishes you see and how to identify them. 

Details of the books mentioned in the text:

Smith's Sea Fishes
Smith M. & Heemstra P., (eds.) 1991. Southern Book Publishers, Johannesburg.
ISBN 186812 032 5
Unfortunately the publisher informs us that this book is now out of print, but you may find a copy at your local bookshop, or possibly on, or search in second hand book shops!

Reef Fishes & Corals East Coast of Southern Africa
Dennis King, 1997. Struik Publishers.
ISBN 1 86825 981 1

A Guide to the Common Sea Fishes of Southern Africa
Rudy Van Der Elst, 1988. Struik Publishers.

Two Oceans- A Guide to the Marine Life of Southern Africa.
Branch G.&M., Griffiths, C. & Beckley, L. 1994. David Philip Publishers, Cape Town.
ISBN 0 86486 250 4

Notes on Underwater Cameras:

Underwater cameras are generally pretty expensive things, but recently a few "budget" ones have come onto the market which you might find ideal for taking snapshots of fish if you can't afford a "real" one - the resulting images will probably never grace the pages of a Divestyle magazine, but at least they are fine for I.D. purposes and to show family and friends all the wonderful things you see "down there". Of course, it has been said that the best photographers can take great pictures using nothing more complicated that a box with a hole punched in it!

Cameras which fit into this category (that I know about) are:

The SeaLife Reefmaster. This Camera is a self contained waterproof Point and Click compact camera that takes 35mm film. A website is available here.

The Bronica Snapper. Again, this is a self contained camera like the one above. Unfortunately, there is no website that I can see, but check the Rodale's article (link further down the page).

Ikelite do a fairly nifty little housing for disposable cameras. A website is available here if you'd like to check out some features. A range of accessories is available for it, such as a flash and close up kit (I'm not too impressed with the close up kit, but I haven't really played with it. The external strobe makes a big difference to the photos though). I have one of these, and sometimes I get some reasonable shots; however, I usually find that a lot of fiddling is necessary to get certain brands of camera to work properly in the housing (often you can either click the shutter or wind the film on but not both - very frustrating!) - find one that works for you and stick to it! I have seen these for hire in the Whaler dive centre at Aliwal. The AquaSnap camera that comes with the casing is a breeze to use though - I wish they were easier to find!

Ikelite now also do a self contained system similar to the Reefmaster and Snapper cameras; a website can be found here. It looks to be quite a nice little setup - A rather nifty looking strobe setup with an adjustable arm is one of the optional extras. Why oh why weren't these cameras available when I bought my housing! Ikelite products have a near legendary customer service attitude, and generally sort problems out quickly and effectively.

A review of some of the cameras can be found at Rodale's Scuba Diving here.

A lot of dive charter companies will hire out a camera for a day - even Sea&Sea and Nikonos cameras in some places.

If you can afford Sea&Sea or Nikonos camera systems (or even a housed SLR) then these are the way to go; however there is quite a steep learning curve as you have to get to grips with f-stops and focusing by turning little knobs. A housed SLR can house an autofocus system more or less eliminating these problems, but the housings are extremely expensive (not to mention the cameras and lenses)! The results are generally a lot better once you get to grips with them, but ironically, before you get used to the settings your buddy with the "cheap and nasty" point and click may be taking photos that are better focused and properly exposed - you'll soon outpace him in image quality though, especially with slide film!