WHAT TO LOOK OUT FOR

Fish ID Basics



Anatomy

To more accurately describe fish species, which can help with their identification, learn the names for the different parts of a fish’s body! You will come across many of these throughout the species descriptions on this web-portal.


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See Fish Morphology!

Colour

For most people, colour is the most obvious and prominent feature of a fish. While colour can be a helpful clue to identifying a fish’s species, it is also important to keep in mind that colour changes and individual variations are common in many reef fishes. For example, species can often look quite different between daytime and nighttime, and throughout different stages of life.

Fish that are dead will also look very different to when they were alive.

Search Fish!
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Day & Night
  • Chinese demoiselle

  • Chinese demoiselle

  • Chinese filefish

  • Chinese filefish

  • Freckled goatfish

  • Freckled goatfish

Life Stages
  • Chocolate hind

  • Chocolate hind

  • Painted sweetlips

  • Painted sweetlips

  • Painted sweetlips

  • Painted sweetlips

  • Painted sweetlips

  • Russells snapper

  • Russells snapper

  • Russells snapper

Individual Variation
  • Dark cardinalfish

  • Dark cardinalfish

  • Dark cardinalfish

  • Dark cardinalfish

SPECIAL FEATURES

Some species are blessed with unique looks!
Here are some examples of species that have something no one else has.

Goatfishes
Two long barbels protruding from under the lips, used for searching through sand.
Longhorn Cowfish
A pair of horn-like features above the eyes.
Blue Hana Goby
Two to three long, flowing filaments from the caudal fin.
Pennant Coralfish
A long, extended first dorsal fin.
Moorish Idol
A very tall, whip-like dorsal fin.
Filefishes
One prominent dorsal spine protruding from above the eyes.
Striped Eel Catfish
Four pairs of barbels underneath the mouth.
Weedy stingfish
Multiple cirri around the bottom lip and chin.
Patterns

There are different types of patterns that appear on fish, many of which have specific names.


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See Fish Patterns!

Just like with colour, patterns can sometimes appear differently on the same species due to day or nighttime colour variations, or other factors. But for some species, some patterns almost never change, giving us a relatively reliable identification feature. These are described in the species profiles for each fish.


1. Saddle Blotch
  • Threespot Grouper

  • Threespot grouper

2. Bar
  • Clark’s anemonefish

  • Doublebar cardinalfish

  • Sailfin tang

3. Stripe
  • Doederlein’s cardinalfish

  • Yellowstripe scad

4. Band
  • Yellowstreaked snapper

  • Twostripe goby

5. Spots
  • Pearl-spot chromis

  • Threespot dascyllus

  • Threespot dascyllus

6. Blotch
  • Mirror butterflyfish

  • Ring tailed cardinalfish

7. Reticulum
  • Honeycomb grouper

  • Longfin grouper

8. Dots
  • Red seabream

  • Red seabream

  • Starry goby

Body Shapes

If you want to really get down to the science, you can start off by looking at the shape of the fishes. Species in the same family will often take on similar body shapes. While this method is accurate, it definitely isn’t easy!

Click on the fish to learn more about them!


 
 
Behaviour

Some species exhibit behaviours which are relatively unique. Familiarizing with the behavioural tendencies of specific species can be a helpful aid in identification. See the examples below!


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PEEK-A-BOO

Although most often observed swimming freely, the milkspotted puffer and Hong Kong pufferfish sometimes hide in sandy bottoms, leaving their bodies only partially exposed. 

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ROOM MATE

Many (but not all) goby species will share burrows with commensal shrimps 

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CLEANERS

Cleaner wrasses are often found dancing around near other fishes, possibly looking for a potential client. 

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FAST SWIMMERS

Yellowstripe scad and other jacks tend to form small aggregations and swim past quickly, rarely pausing to linger. 

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PERCHING

Many groupers will perch atop corals or rocks, or hover just above the sea bottom, sometimes observing divers from a distance. The chocolate hind is a frequently encountered example.

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MORE PERCHING

Perching is also a favourite of sandperches and hawkfishes, posing neatly and in plain view on rocks, rubble or sandy bottoms. 

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HOVERING

From juveniles to adults, hovering behaviour can also be observed in the banded goby! 

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PLAY DATE

Young wrasses and goatfishes sometimes form small schools of roughly ten or so individuals, sometimes with juveniles of other species. 

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RARELY ALONE

The pearl-spot chromis is almost always found in schools when encountered during daytime, numbers ranging from ten to hundreds. Similar-looking species such as the smokey chromis sometimes join in!

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SWIMMING CROOKED

Not all fish swim straight! Floral wrasse, for instance, lean sideways when they swim, appearing to press one side of their bodies against corals or rocks. 

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ALSO RARELY ALONE

Schooling in large numbers can also be observed in the Chinese demoiselle and rabbitfishes.

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SWIM-STOP-SWIM

The monocle bream and some seabreams, such as the red seabream, move with a funny pattern of swim-stop-swim, breaking up their path with abrupt stops.

Behaviour

Some species exhibit behaviours which are relatively unique. Familiarizing with the behavioural tendencies of specific species can be a helpful aid in identification. See the examples below!

Habitat

Each dive site provides a range of habitats for species to choose from. Knowing the habitat preferences of fishes can give you a hint to what you might find at different dive sites!


Search Dive sites in HK