Cryptic Fish

Cryptic fish are those that are often hard to see - either because they bury themselves in holes in the sand, or because their colouration enables them to blend into the background.

Cryptic fish include so-called cryptobenthic fish such as blennies and gobies, which live in holes in the sand. They are known as detritivores, a name that means they feed on waste products left behind by other reef creatures.

Seahorses are also included in this group because most of them rely on their cryptic colouration or appendages for camouflage. They hare very slow swimmers and have to rely on camouflage to hide from predators. Razorfish also use camouflage and body orientation to hide.

Seahorse

Harlequin ghost pipefish

Seahorses and pipefish

Family Syngnathidae

Seahorses and pipefish are small elongate fish encased in bony plates.  Looking like the knight on a chess board, the seahorse is characterised by its angled head.  As they are not strong swimmers, seahorses rely on a prehensile tail to hold onto algae and coral.  During mating the female seahorse deposits eggs into a pouch on the male's abdomen where they are fertilised and start to develop.  After a few weeks, during which the male's pouch becomes quite swollen, he "gives birth" to up to one hundred young.

Male pipefish do not have pouches.  Instead, the female adheres the eggs to the underside of the male's abdomen where they remain until hatching.

Both seahorses and pipefish undergo elaborate courtship rituals every day to re-establish bonds with their partners.

The tube-like mouth of seahorses and pipefish is used like a pipette to suck in tiny plankton organisms.

Razorfish

Family Centriscidae

Looking like a school of swimming knives, razor fish swim in an unusual vertical posture.  This allows them to hide amongst the spines of sea urchins or between branches of coral.  The body of a razorfish is extremely thin, almost transparent and enclosed in heavy plates.  Their swim bladder can easily be seen if a light is shone behind them.  They are closely related to seahorses and pipefish and use their mouths to suck in zooplankton.

Blennies

Family Blennidae

These small, secretive fish live amongst coral and coral rubble.  They often have fleshy crests, or cirri, as they are known, growing from above the eyes and nostrils.  Most blennies are detritivores, scraping filamentous algae for detrital matter.  There are a few carnivorous species of blennies, the most notable being the mimic or sabre-toothed blenny.  The sabre-toothed blenny mimics the colour patterns of the cleaner wrasse.  As it approaches a larger fish it uses its large sabre teeth to take a bite out of the side of an unaware fish waiting to be cleaned.

Sleeper-headed goby

Gobies

Family Gobiidae

Gobies are small bottom-dwelling fish that often go unnoticed.  With over 1600 species, gobies are actually the largest family of fish in the world.  Living amongst coral rubble and sometimes in burrows in sand, gobies can be distinguished from blennies by their pelvic fins, which form a disc-shaped cup.

Gobies feed mostly on small invertebrates; many of the sand-dwelling gobies take large mouthfuls of sand and sift out the invertebrates or minute algae.

A number of gobies live in symbiotic relationships with different species of alpheid shrimp.  The gobies have good eyesight and are very alert.  The shrimp however, has poor vision but remains in contact with one of the gobies by using its long antennae.  Should danger threaten, the retreating fishes alert the shrimp and they all retreat into the burrow.  In return, it is the role of the shrimp to do most of the making and maintenance of the burrow.