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 (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
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
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.