EXPLAINER – The Eastern Blue Groper: A NSW coastal icon

THE eastern blue groper (Achoerodus viridis) is endemic and one of the most iconic fish species found in New South Wales coastal waters.

Recognised for its striking cobalt blue colouration and curious nature, this fish holds ecological, cultural, and conservation significance.

Its visibility and frequent non-aggressive interactions with snorkelers and divers have made it an icon of the NSW rocky reefs and was proclaimed the official fish emblem of NSW in 1998.

Their gentle and curious nature makes them the highlight of any underwater experience.

They are regularly encountered in Port Stephens along the rocky coast and around the offshore islands.

Although colloquially referred to as a “groper,” A. viridis is technically a large wrasse of the Labridae family, a group known for their vibrant colours, interesting biology and dynamic sexual phases.

It should not be confused with the tropical grouper (Epinephelus spp.).

Meet the Eastern Blue Groper

The eastern blue groper (Achoerodus viridis) can grow up to 1.2 m long and can weigh over 20 kg.

They have prominent fleshy lips and large peg-like teeth.

Eastern blue groper start life as plankton before settling into seagrass beds or other appropriate habitat where they develop into an all-female cohort, reaching sexual maturity between one and four years and breeding between July and September.  They will all remain as females until around 18 years old or a length of 50 to 60 cm when some but not all, change sex to males, reaching a maximum recorded age of 35 years in NSW, but could be longer.

This sex change is a result of an extraordinary biological process known as protogynous hermaphroditism.

If the large male is removed (by fishing or natural mortality) the next-ranking female changes her behaviour and physical appearance over weeks to become male and ensure a stable breeding population.

As juveniles, the eastern blue groper displays green/brown hues and as adult females a reddish-brown coloration, with the signature cobalt blue colouring being the terminal phase when/if they transition to become males.

Being slow growing and long lived (18 to 35 years before changing sex from female to male) makes the blue groper vulnerable to fishing pressure and environmental change.

The sudden removal of the dominant males through fishing can lower productivity causing social disruption and disrupted fertilisation rates.

Fishing pressure can also reduce the numbers of large female fish in the population.

A reduction in available large females able to change sex could reduce the number of available spawning males.

This situation may persist until a remaining female attains that critical size (DPI-NSW Stock Status Summary – Blue Groper 2024).

The International Union for Conservation of Nature (IUCN) Red List classifies Blue Groper as “Near Threatened”, due mainly to loss of key habitat and historical overfishing.

The NSW DPI stock status summary noted that the stock structure is not well understood but considered the groper stock to be sustainable but subject to other potential risks such as climate change and warming seas.

Since the mid-1990s, this species has not featured highly in catch records so it may not be a heavily targeted species by recreational fishers.

Where do they live?

The blue groper ranges from Hervey Bay in Queensland to Wilson’s Promontory in Victoria, but they tend to be more common along the NSW coast.

They inhabit shallow rocky reefs, headlands, and kelp forests.

Blue groper generally live in harems with a few females, several juveniles and one male presiding over a small home range. Juveniles typically inhabit estuaries and shallow seagrass beds which provide food and shelter from predators.

As they mature, they migrate to deeper, more exposed rocky reef areas that provide both habitat and hunting grounds.

The blue groper displays high levels of site fidelity (remaining on the same site for all or most of their lives).

As a result, individuals become recognised and cherished by divers and snorkellers who often “adopt” and name local gropers.

The blue groper is primarily diurnal (hunts by day and sleeps at night) and known for its territorial behaviour.

Their diet primarily consists of hard-shelled invertebrates such as molluscs, crabs, echinoderms, prawns, and worms.

They use their peg-like teeth to dislodge prey and their pharyngeal (crushing) plate in their throat to crush prey before swallowing and larger shell fragments are expelled through the gills.

The blue groper is a keystone species playing an important ecological role in maintaining the balance of biota on rocky reefs.

While the Blue Groper does eat sea urchins, according to recent studies at the University of Newcastle the groper has a limited role in controlling the long spined sea urchin (Centrostephanus rodgersii) considered by some to be responsible for destroying kelp beds and creating “urchin barrens”.

Conservation and legal protection

Their large size and visibility made them an easy target for fishers but over time growing public appreciation for their beauty and ecological importance, and concerns over declining numbers led to calls for better protection.

All fishing of the groper was banned in NSW in 1969.  Line fishing and commercial fishing, but not spearfishing, was reinstated in 1974 with recreational bag limits of two fish per person, with a minimum size of 30 cm.

The commercial fishery was closed in 1980.

Fifty years later in February 2024, following spear fishing incidents in Sydney and Jervis Bay, the NSW Government announced a total fishing ban on groper by any method for 12 months except for Aboriginal cultural fishing.

In February 2025 the NSW Government announced that, following scientific advice and community feedback, the total ban would continue for a further three years starting in March 2025 allowing further research and monitoring of the impacts from the climate crisis, such as seawater warming and acidification on this species.

This aligns NSW with Victoria where blue groper is fully protected.

Any person contravening the regulations may face a $500 fine for a penalty infringement notice and/or a maximum court enforced fine of up to $22,000 and/or six month imprisonment for a first offence and up to $44,000 and/or 12 month imprisonment for a second offence.

At the time, the NSW Minister for DPI stated that “these fish should be admired not targeted”.

It should be noted that it is an offence to interfere with any protected species in any way.

The road ahead

Since protective regulations were introduced, populations in many areas have shown signs of recovery.

Divers frequently encounter large individuals in marine reserves, a testament to the effectiveness of habitat protection.

However, conservation is an ongoing process.

Maintaining healthy populations of Achoerodus viridis (together with many other species) will require continued vigilance, adaptive management, and public support.

Strengthening marine protected areas, improving enforcement, and mitigating climate impacts are all critical steps in securing the future of this iconic species.

By Iain WATT, President, EcoNetwork Port Stephens