SPECIES SPOTLIGHT - SPANGLED EMPEROR

Spangled Emperor

LETHRINUS NEBULOSUS Other names: Spangley, Iodine Bream, Tricky Snapper, North-West Snapper, Yellow Sweetlip, Sand Bream, Sixteen Pounder.

BY DR JULIAN PEPPERELL, PhD. Photos Graeme Cox

Dr. Julian Pepperell, PhD, is one of the best-known marine biologists in the world and a leading authority on Marlin, Sailfish, Tuna and Sharks.

There are around 30 species of Emperors in Australian waters, the Spangled Emperor being one of the more prolific members of the Lethrinid family. On a global scale, the Spangled Emperor is very widespread, ranging from the Red Sea and East African coast to southern Japan and the islands of the Western Pacific. The species has long been recognized in Western Australia, and while a genetic study published in 1993 suggested that the Western Spangley is actually a separate species – Lethrinus choerorynchus, this has not been adopted by Western Australian Fisheries.

The Australian distribution of the Spangled Emperor in Australia is tropical to sub-tropical, ranging from as far south as Perth in the west right around Northern Australia to central NSW - a distribution that helps to explain why this single species has been dubbed with so many different common names depending on where it is caught.

There is another common Emperor in both Eastern and Western Australia that may often be confused with the Spangled, the Blue-lined Emperor, Lethrinus laticaudis, also known as the Grass Emperor, or simply, ‘Sweetlip’. Both species have blue markings on their face, and while the overall colouring is also similar, Spangleds tend to have brighter yellow fins and pale blue spots or ‘flecks’ covering most of their flanks while Blue-lineds are more uniform coloured with darker fins. Spangled Emperors can change colour quite rapidly though, often developing brown blotchy stripes over the body when stressed.

Like other unrelated reef fishes, Spangled Emperors appear to change sex from female to male during their lives. A study at Ningaloo Reef, WA showed that all small fish less than about 25 cm in length are female. By a mean length of 28 cm (two to three years old), many of these change sex to males, although some remain as females but do not mature until about 39 cm long aged from three to five years old.

The minimum legal size for Spangled Emperor in WA is 41cm, and in QLD is 45cm, which allows protection of all males and at least half of the females in the population until after maturity.

Larval Spangled Emperor swim around in the water column, moving from the reef to inshore areas, eventually settling in seagrass beds for their early lives, using their acute sense of smell to find these nursery grounds.

Spangled Emperors grow to quite hefty sizes. The International Game Fish Association (IGFA) lists the current world record for the species at 9.45 kg (and an overall length of 82 cm) for a specimen caught off southern Japan in 2002. Weights of ‘over 10 kg’ are cited by some Australian fishing writers, but fish of that size do not appear in official record lists. The Spangled Emperor is quite a long lived fish, with several studies agreeing with maximum ages of over 20 and up to 30 years old.

Because of their recreational fishing importance, a study of movements of Spangled Emperor was recently carried out in the Ningaloo Reef Marine Park, Western Australia, primarily to investigate the adequacy of the size of sanctuary zones within the park for that species. Researchers tagged 84 individual fish with acoustic tags and tracked their movements over the next two years or more via underwater ‘listening’ posts. They found that the average home range was 8.5 square km, but found no relationship between the size of tagged fish and degree of fidelity to home sites. Fish that were tagged within sanctuary zones spent around 80% of their time within those zones. Home ranges changed through time, however, such that 60% of tagged fish had moved outside of sanctuary zones within a year.

In a smaller study in New Caledonia, only six fish were tagged with acoustic tags in an area where boats moored, with larger fish showing strong site fidelity over 6.5 months, moving away to feed at night but returning during the day. In an interesting result, it was noted that these fish tended to stay near the mooring area much more on weekends and school holidays, which was when feeding of fish by humans was most active. While this

ABOVE: A juvenile Spangled Emperor caught on hook and line (prawn bait) under a float at Ettalong, NSW, March 2010. (Image: Robyn Ashton)

result was not especially surprising, the authors called for stricter measures to control feeding activities within Marine Protected Areas to reduce the impact on the natural behaviour of fish.

The Spangled Emperor seems to be a fish that divides opinion over its edible qualities. On one hand, anglers I have met, mainly in northern Queensland, insist that Spangleys have a somewhat metallic or iodine taste, hence the moniker ‘iodine bream’ in those locales.

However, this reputation may be based more on rumour than reality. I have personally eaten them and not experienced any such taint and they are certainly happily eaten with gusto elsewhere. One person whose opinion I would value in this regard is Ern Grant, author of the legendary book ‘Grant’s Guide to Fishes’. He has undoubtedly dined on many a Spangley and rates them a top grade food fish holding its own with other popular reef fish.

Added to that, other fishing writers in Western Australia also praise the Spangled (and Blue-lined) Emperors as being ‘among the best eating fish in the sea’, especially for fish and chips.