southern blue devil
Article by Thomas Lachlan Mayo
Diver’s delight
The Southern Blue Devil (Paraplesiops meleagris) is an iconic temperate reef species, easily recognisable by their striking iridescent blue spots, dark blue body, large dark eyes, and elongated fins. This visually spectacular species is a favourite among recreational divers, often providing stunning photographic opportunities.
Image: Simon Bryars
No place like home
The Southern Blue Devil is a shy but inquisitive, cave dwelling species, inhabiting cracks, crevices, and ledges of coastal temperate reefs. They naturally exhibit a high level of site fidelity, with some individuals inhabiting the same reef for decades, aggressively protecting it from competition. Their preference for caves and ledges provides them with protection from predators, and a base to return to after feeding on small fish, invertebrates, and crustaceans.
Image: Simon Bryars
Much like the Harlequin fish, which inhabits many of the same waters, the natural iridescent blue markings of the Southern Blue Devil have become a source of great interest among marine scientists. Using historical photographs gathered from recreational divers, researchers have been able to identify the same fish in different photographs, and subsequently, track their movements as well as estimate age and home ranges.
Indicators of ecosystem health
The Southern Blue Devil only reach a maximum of around 36 cm in length but have been found to live for up to 60 years. The longevity and site attached nature of this species means they play a crucial role in maintaining the balance of prey species and larger food web dynamics over long periods of time. Reefs where they are present can be an indication of a well-functioning ecosystem. Thus, experts often refer to their abundances as an indicator of greater ecosystem health.
Image: Simon Bryars
Conservation status
While the Southern Blue Devil are not currently listed as endangered, like many marine species, they face threats from habitat destruction, pollution, and climate change. Being long lived and slow to reach sexual maturity, any disruption can have long and lasting impacts on their populations. Conservation efforts to protect the habitats of these species is essential to ensure they thrive and continue to inspire future generations of marine enthusiasts.
Image: Simon Bryars
Same but different
The Southern Blue Devil also has two close relatives; the Eastern Blue Devil (Paraplesiops bleekeri) and the Western Blue Devil (Paraplesiops sinclairi), which inhabit the waters of eastern and (south) western Australia respectively. All three species share many characteristics such as their iridescent blue markings and elongated fins. However, each have developed their own variations; the Eastern Blue Devil have developed a banded pattern and bright yellow fins. While mature Western Blue Devils often display a yellow pectoral fin.
Image: Mike Jones
All three species share many characteristics such as their iridescent blue markings and elongated fins. However, each have developed their own variations; the Eastern Blue Devil have developed a banded pattern and bright yellow fins. While mature Western Blue Devils often display a yellow pectoral fin.
Image: J. Martin Crossley
Fast Facts:
Species: Paraplesiops meleagris
Size: < 36 cm
Age: < 60 years
Diet: Small fish, crustaceans, and invertebrates
Habitat: Ledges and caves of coastal temperate rocky reefs
Depth: < 45 metres
Image: Simon Bryars
