The Blackspot Tuskfish is just one of around 225 members of the wrasse family, Labridae, that are found in Australian waters, expanding to well over 500 species found worldwide. In fact, Labridae is the second most ‘speciose’ fish family in Australia. Now, while all of the members of this very large family are officially called ‘Wrasses’, the common names for many of them can be quite confusing. To see what I mean, each of the following names apply to at least one or more ‘wrasse’ species: Groper, Rainbowfish, Tubelips, Cleanerfish, Foxfish, Pigfish, Hogfish, Combfish, Razorfish, Knifefish, Double Header, Bluebone, Maori-Wrasse and yes, Tuskfish. For that reason, it’s probably better to refer to members of the family as Labrids.
It is a particularly widespread Labrid, occurring from the Ryuku islands, off southern Japan, through Indonesia to Australia, and in the Indian ocean, possibly as far as Mauritius. Its Australian distribution is typically tropical/sub-tropical, covering the coastal northern half of the continent from just south of Shark Bay in the west to around the Gold Coast in the east. There are several possible records from northern NSW, and a single record from Sydney, which is highly dubious.
Another relevant example, by the way, of why common names of fish can be confusing is that, in addition to the Blackspot Tuskfish, another member of the Labrid family, Austrolabrus maculatus, a much smaller, temperate species, is known as the Black-Spotted Wrasse. Tricky, non?
The Blackspot Tuskfish is one of the larger wrasses, growing to a reputed length of 90 to 100 cm. With the possible exception of some of the larger members of the family, such as Blue and Baldchin Groper, the biology of the majority of the Labrids is poorly understood. Most are small fish of little or no commercial importance, so studies, if any, tend to be confined to underwater observations of behaviour. However, perhaps because of its broad geographic distribution, size and conspicuousness, the blackspot Tuskfish is somewhat of an exception to the rule. The species has attracted some scientific attention in the Ryukyu islands off southern Japan, where they are a highly prized table fish and are a target species of a specialised nighttime spearfish fishery.
Most Labrid species are highly sexually dimorphic, meaning that males and females are very different from each other. Male Labrids are nearly always much more elaborately coloured than females, and they are also normally larger. This is because they change sex, all fish beginning life as females, then turning to males when they reach a certain size, the technical term for this being the terminal male phase of the life cycle. A single male will usually tend a ‘harem’ of several females. Blackspot Tuskfish can be identified by a large dark spot, or ‘ocellus’ at the base of the rear one-third of the dorsal fin. They also usually have blue spots on each scale, often forming blue horizontal stripes along the body, and a blue line at the base of the anal fin.
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Blackspot Tuskfish and four other sympatric Labrid species in Shark Bay, WA were also the subjects of a Ph.D study by David Fairclough of the University of Western Australia. Focusing just on the Blackspot Tuskfish for the purposes of this article, the study showed that female fish mature at about 25 cm long, or
an age of 3.5 years. Around 50% of females will then have changed to males by a size of 55.5 cm, at which size they average 10 years of age. The Blackspot Tuskfish is somewhat famous in being one of relatively few species of fish in which apparent use of tools has been observed. Yes, really! This is based on an observation in 2006 by a diver in the Keppel region of the Great Barrier Reef. Alerted by a cracking noise, the diver noticed a Blackspot hovering over a sand patch, near a rock, with a cockle in its mouth. He snapped off a group of photographs showing the fish rolling on its side and whacking the cockle against the rock a number of times until the shell broke. So, in the sense of the definition of tool use by Chimpanzee expert, Jane Goodall – being “the use of an external object as a functional extension of the mouth or hand in the attainment of an immediate goal” – the use of a rock as an anvil certainly qualifies.