What Critter Is It?

Fish are sometimes stranded alive in pools on outgoing tides, but usually they are dead, and a rare feast for seabirds. You might occasionally also find freshwater species on metropolitan beaches following rains that have washed fish, such as European carp, out of the Torrens.

Porcupine fish

Porcupine fish (a.k.a. balloon fish, puffer fish) Diodon sp

Best not to step on a dead, dried porcupine fish! It has nasty, long sharp spines. In a live fish the spines provide defence against predators, as does its ability to inflate its body, making the spines stick out – like an echidna in defensive mode. These fish are not built for speed.

 

 

 

Toad Fish Tetractenos

Toadfish – don’t eat!

These fish grow to about 15 cm (this one was about full size) and are common in shallow water in southern Australia. Like other members of this family, toadies are poisonous.

 

 

 

 

 

Short-headed Lamprey (a.k.a. Australian Lamprey) Mordacia mordax

Lamprey

Looking like an eel, these fish grow to about 50cm in length and move from marine to fresh water to breed. In the sea they parasitise other fish. Most fish have jaws, but Lampreys are blood sucking and have a round funnel-like mouth with many small sharp teeth.

All crabs belong to the group called the Decapoda – Latin for ‘ten legs’.

There are lots of crab species in the Gulf, and they range in size from tiny to quite large. Most have hard shell (carapace) unless they are moulting. This happens as the crab is growing. Calcium is reabsorbed from the old shell, which gradually becomes softer, and is used to grow its next shell. When the new shell is ready the old shell is cast off, and the new shell hardens quickly. Sometimes the soft, old shell is washed up. Hermit crabs don’t have a hard carapace, and they use empty marine snail shells to protect their soft bodies. As they grow they need to find larger snail shells. If you are collecting shells on the beach, be sure to check that there is not a hermit crab in residence!

The Blue Swimmer is probably the best known crab, and is sought after because it is abundant and tasty! If you see one in the water while you are swimming, or in a tidal pool, don’t get too close – a nip from their claws is painful.

Sand crab carapace – note the two dark red sots

Sand crabs are pale reddish with two darker spots on the carapace.

 

 

 

 

 

 

 

 

 

Spider crabs range greatly in size, but characteristically have really long legs.

Spider crab near Henley Jetty – approx 20 cm across the carapace

 

 

 

 

 

 

 

 

 

 

Tiny spider crab – approx 1 cm across the carapace

 

 

 

 

 

 

 

 

 

 

 

Rock crabs are smaller and chunkier than the swimmers and spider crabs, but are really good at wedging themselves under rocks and in cracks.

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