Fish in focus - Breaksea Cod

Glenn Moore's blog | Created 5 years ago

As proud Western Australians, to start off in 2013 we will be highlighting a group of very special fishes – endemic species – those found only in Western Australia.  This is the first of those.

One of a kind - Breaksea Cod

Epinephelides armatus (Castelnau, 1875)

Status: Near Threatened

Most of the more than 100 species of cods and gropers (family Serranidae) in Western Australia inhabit our northern waters, but the Breaksea Cod is one of our more southerly species.  Of course there are other temperate species of cods (around a dozen species in WA), but this is the only species in the genus Epinephelides, so it really is one of a kind.  Breaksea Cods live on coastal reefs between the Recherche Archipelago (Esperance area) to Shark Bay.  They are often seen tucked into a cave down to around 35 metres, but they have also been collected by trawl in much deeper water to at least 100m.

A large Breaksea Cod fish swimming

Breaksea Cod - Epinephelides armatus (Castelnau, 1875)
Photo by Barry Hutchins. Image copyright WA Museum.

This species lives for about 20 years and reaches maturity at 3-4 years (females ~ 30 cm; males ~ 25 cm).  They reach around 55 cm in length and males grow faster and larger than females.  Unlike many other cods, which change sex as they grow (sequential hermaphroditism), it appears that Breaksea Cod are born as separate sexes (gonochoristic).

Breaksea Cods have distinctive scales with pale centres, but perhaps the most distinguishing characteristic is the large black blotch around the anus – giving rise to the common name that many fishermen know it as, Black-arse Cod.  The Breaksea Cod is popular among fishermen, although it is rarely targeted specifically.  This species is also popular among SCUBA divers and I’m no exception.  It is usually found perched on the reef waiting to ambush an unwary passing fish.  I’ve always found it to be an inquisitive and unassuming fish that happily invades your personal space to see what you are doing.  One thing that always fascinates me about this species is the range of colours it can have – anything from shades of yellow, pink, green, brown and grey.

This special Western Australian fish was first recorded from the ‘Swan River’, presumably referring to the Swan River Colony, by Reverend Bostock.  Bostock was a naturalist clergyman who regularly donated specimens to Count de Castelnau. [The seemingly conflicting combination of Bostock’s interests was common at the time, given that an understanding of evolution was in its infancy and a belief in creation was still the norm.]  Castelnau was a French diplomat based in Melbourne, who also filled the role as Australia’s only resident ichthyologist at the time.  Castelnau described the Breaksea Cod as a new species in a publication titled Researches on the Fishes of Australia in 1875.  His name is written after the species name (see above) to reflect that.

A small Breaksea Cod resting

Breaksea Cod - Epinephelides armatus (Castelnau, 1875)
Photo by Barry Hutchins. Image copyright WA Museum.