Log Transcript

The lives of the more than 25,000 species of bony fishes suspended and dispersed among the oceans of the world today, are all touched by a unique group of boneless fishes, the sharks and rays. Compared to the lesser known rays, sharks have taken on a larger than life role in both our imaginations and sometimes daily lives, due primarily to sensationalized media coverage, whereas the world of the ray remains mysterious.

Existing in the shadows of their sharp-toothed cousins for whom they are a major food source, rays do not appear to command our attention in the same way that sharks do, nor have they left behind as much of a fossil record as the bony fishes, due to their cartilaginous structure. Most of what we know about them comes from a few teeth and the occasional fossilized skeleton that has managed to survive under fortuitous geological conditions.

But rays are a remarkable group of fishes represented by more than 500 species with important features that separate them from sharks. The eyes are positioned on the top of the head, providing an excellent view of the horizon and the water above. Rays are blind to their lower surface and detect prey items beneath their bodies with a well-developed olfactory system in front of the mouth. The main body is highly flattened and the greatly enlarged pectoral fins form a body disc that may be wedge shaped, oval, circular or triangular, rays often use this disc to trap prey items.

This Shovelnose Ray is host to two remora fish. Remoras utilize a sucking disk on the top of their head to attach to a host fish in the hope of picking up any food scraps.

Photo: Chris Johnson

It's believed that rays are direct descendents of modern day sharks, which have evolved into a bizarre assortment of sizes and shapes that include guitar fishes, skates, electric and sting rays, eagle rays and the magnificent giant manta ray. A massive fish that swims the open ocean on a wingspan of more than 18 feet, and that the odyssey crew have come across on many occasions.

Rays are widespread in almost all bottom-dwelling communities of the oceans, inhabiting offshore pelagic environments and extending into many inland freshwater habitats. The other day, we experienced a close encounter in the shallows of the harbor of Doctor's Gully with the unusual Shovelnose ray. It has a flattened ray-like head and a muscular shark-like tail with well-developed dorsal and tailfins. To the untrained eye, this ray could easily be mistaken for a shark.

The scientific knowledge of rays is gradually increasing, however unknown species continue to lurk in the oceans depths, particularly in the Indo-Pacific where more than 50 new species have been discovered in the last decade. When trying to identify a ray, it's important to note its external features. Is the disc large or small compared to the tail? Is the head separate from the disc? Is the tail broad or whip like? With more than one third of the worlds ray fauna found in the waters surrounding Australia and Indonesia, the crew are recognising the value in these initial important observations in order to attempt to identify the family group of the rays we encounter in northern Australia.

This is Genevieve Johnson speaking to you from the Odyssey.

Log by Genevieve Johnson

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