Halimeda, Hot Beds of Biodiversity!

In 1982, Australian Museum researchers studying fish larvae were towing a plankton net near Lizard Island (Research Station).

They accidentally encountered a bed (also known as a meadow) of the coralline alga Halimeda. The bed was at a depth of 35 m - 40 m. When the net reached the surface it contained 51 adult and juvenile fishes that had been sheltering in the seagrass.

These fishes comprised 14 species, two of which (a goby and cardinalfish) were species apparently not previously described. The goby was a member of a new genus and species, Minysicya caudimaculata described in 2002 by Dr H.K. Larson of the Northern Territory Museum. This was an almost unheard of ratio of new species in such a small catch. With this in mind Australian Museum researchers, led by Dr J.M. Leis, returned to the Lizard Island area in 2001. They conducted two more collections in Halimeda beds at depths of 23 m - 27m.

The two collections produced an astonishingly interesting group of fishes. A total of 378 fishes (35 species in 18 families) were collected by the divers. Several fishes that were either undescribed or new to Australia were found. The likely new species of cardinal fish encountered in 1982 was again collected along with specimens of another apparently new cardinal fish species (genus Fowleria). Drs G.R. Allen and T. Fraser described the first in 2006 as Neamia articycla, and are studying the Fowleria specimens.

Four specimens of a potentially undescribed goby of the genus Hetereleotris were captured. This genus was not previously reported from the Australian mainland . They are currently being studied by Dr D.F. Hoese, of the Australian Museum. A single goby of an undescribed, but previously known species was also taken.

Two species of moray eel and one of a worm eel were taken. These could not be identified by Australian Museum scientists. Photos and x-rays of these eels were sent to the world's expert on morays and worm eels, Dr J. McCosker, of the California Academy of Sciences. After study, Dr McCosker identified one as a new Australian record and another as a colour form of a known species that he had not seen before. A specimen of the filamented flasher wrasse Paracheilinus filamentosus was captured. This species had not previously been recorded from Australia.

In the three collections (one in 1982 and two in 2001), about 50 species were captured. Of these, eight were new to Australia, and at least five represent undescribed species. This remarkably high ratio of unknown species shows the rich biodiversity that exists in Halimeda beds in the inter-reef areas. It also shows how little we know about this habitat, which is extensive in the Great Barrier Reef area, covering hundreds of square kilometres of the Lizard Island area alone. If so many fish species new to Australia can be found in just three small collections, then there is obviously much more to discover. Not all the interesting fishes from the Great Barrier Reef are on the coral reefs!

A complete listing of all the fishes collected in the 2001 fieldwork is given in the table below. Thank you to Dr G. Allen (Western Australian Museum), Dr D. Bellwood (James Cook University), Dr A. Gill (Natural History Museum, London), Rudie Kuiter (Zoonetics.com) and Dr J. McCosker (California Academy of Sciences) for their help with fish identifications and to GBRMPA for the permit to do this work.