© Baker, J.L. (2009) Marine Species of Conservation Concern in South Australia Full citation Baker, J.L. (2009) Marine Species of Conservation Concern in South Australia: Volume 1 - Bony and Cartilaginous Fishes. Report for the South Australian Working Group for Marine Species of Conservation Concern. J. Baker (consultant); Science and Conservation Division, and Coast and Marine Conservation branches of S.A. Department for Environment and Heritage (DEH); Marine and Coastal Community Network of S.A. (MCCN), and Threatened Species Network (TSN). Web version published by Reef Watch, South Australia.

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Western Wirrah

Family Name:	Serranidae
Scientific Name:	Acanthistius serratus (Cuvier, 1828)
Recommended Status in S.A:	Data Deficient
Rationale:  Included here because (i) the south-western species Western Wirrah has a limited distribution in South Australia, having been recorded in this State only in the Great Australian Bight, with no data on population size; (ii) the species is site-associated with shallow subtidal reefs, which can increase the vulnerability of populations in some areas to site-specific impacts; (iii) Western Wirrah is a member of the Serranidae, a family of fish whose life history characteristics increase the vulnerability of populations to decline. Serranids are generally slow moving, benthic, reef-associated fish that reproduce as protogynous hermaphrodites, and maintain specific population structures. These characteristics make Serranids vulnerable to capture by a number of fishing methods, and susceptible to other site-specific impacts; (iv) the species is taken in by recreational fishers in some parts of the range (e.g. W.A.), with inadequate controls over the numbers taken; and (v) data are lacking on the distribution and relative abundance in S.A., and on the extent of threatening processes over the range.

Page Contents

Current Conservation Status

No listings known

Distribution

Southern Australia

Acanthistius serratus is confined to south-western Australia, from the eastern Great Australian Bight in S.A. through to Shark Bay in W.A. (Kuiter, in Gomon et al., 1994).
The species is considered moderately common in W.A. (Kuiter, in Gomon et al., 1994; Edgar, 2000). It is noted that, during a recent survey of nearshore habitats in south-western Australia, Western Wirrah were recorded in low abundances (i.e. less than 0.1 fish per 100 square metres) (Valesini et al., 2004).

South Australia

The Ceduna area in the eastern Great Australian Bight is reported to be the eastern limit of the geographic range (Kuiter, in Gomon et al., 1994).
There are few published records from South Australia, and all are from the Great Australian Bight. For example, at the Nuyts Archipelago islands in 2002, only 1 Western Wirrah was recorded during a survey that covered more than 70 transects (Shepherd and Brook, 2003b). Previously, during two surveys of the Investigator Group Islands on the west coast of S.A., the Western Wirrah was not recorded at all (see Kuiter, 1983; Branden et al., 1986).

Habitat

Western Wirrah is an inshore species (Paxton et al., 1989) that occurs in exposed coastal reef areas, particularly in caves, to depths of around 40m (Hutchins and Swainston, 1986; Gomon et al., 1994).
Juveniles commonly live in shallow rock pools (Kuiter, in Gomon et al., 1994).
During a recent survey of nearshore habitats in south-western Australia, Western Wirrah were recorded on reefs with dense macroalgae cover, but also in seagrass beds of medium density (Harvey et al., 2004). During another recent study in south-western Australia from summer 2000 to spring 2001 (Valesini et al., 2004), Western Wirrah juveniles were recorded in low abundance, in a habitat type characterised as “moderately to fully exposed to wave activity, with (macroalgae-covered) reefs present within 50m of the shoreline and also further offshore”.

Notes on Biology and Behaviour

Age and Growth

Western Wirrah grows to around 50cm (Kuiter, in Gomon et al., 1994).
Maximum recorded weight is 2.77kg (Hutchins and Swainston, 2001). Two of other record sizes are specimens of 1.70kg (taken at Fish Creek in W.A., in 1987), and 1.113 kg (taken at Direction Bank in W.A., in 1998) (Australian Anglers Association, 2005; Australian Anglers Association, W.A. Division, 2005).

Diet

Western Wirrah is carnivorous (Shepherd and Brook, 2003b).

Behaviour

The species is considered to be shy, showing a preference for caves, and therefore not often seen (Kuiter, in Gomon et al., 1994; Edgar, 2000).
During a survey of nearshore habitats in south-western Australia, Western Wirrah were recorded only at night (Valesini et al., 2004), which may indicate that the species is more active nocturnally than diurnally.

Reproduction

Most species in the Serranidae are protogynous hermaphrodites, as are most members of the sub-family Anthiinae (to which Acanthistius likely belongs) (P. Heemstra, South African Institute for Aquatic Biodiversity, pers. comm., 2006). Protogynous hermaphrodites first mature as females and, after spawning one or more times, they will then change sex, spawning thereafter as males (Heemstra and Randall, 1999).
The larvae are reported to settle on the bottom at a size between 10.5 and 23.0 mm BL (Neira et al., 1998, cited in Froese and Pauly, 2006).

Fisheries Information

No information on commercial fisheries could be found for this report. The Western Wirrah is not targeted commercially because the flesh is considered poor quality. The closely related south-eastern Australian species Eastern Wirrah Acanthistius ocellatus is commonly known as “Old Boot”, due to its tough, unpalatable flesh (Sea-Ex Australia, 2005), and Western Wirrah attracts the name “Rottnest Boot” in W.A.

Recreational

Although the species is considered to be a poor quality table fish (Gomon et al., 1994; Edgar, 2000), it is taken by recreational fishers in some areas (Henry and Lyle, 2003).
In Western Australia, a Fisheries Department survey conducted in 1996-1997 between Augusta and Kalbarri, reported that up to 416 (SE 139) Western Wirrah were kept by recreational boat fishers during that period, and 105 were released (Sumner and Williamson, 1999).
In some parts of W.A., surf fishers catch Wirrah (e.g. Surf Casting and Angling Club of W.A. Inc., 2002, 2006), which are reported to be “ubiquitous” at some locations frequented by surf fishers.
Some fishing clubs keep records of the maximum sizes caught (e.g. Australian Anglers’ Association Inc. W.A. Division, 2003; Australian Anglers Association, 2003).
In south-eastern Australia, the related species A. ocellatus is occasionally taken by spear fishers, and it is likely that A. serratus is also speared at some of the more accessible nearshore reef areas in south-western Australia. It is noted that the record-sized specimen was taken by spearfishing (Hutchins and Swainston, 2001).

Vulnerable Characteristics of the Species

The south-western species Western Wirrah has a limited distribution in South Australia, known in this State only from the Great Australian Bight.
Western Wirrah is a member of the Serranidae, a family of fish that have life history characteristics that increase the vulnerability of populations to decline. For example, Serranids are generally slow moving, benthic, site-associated fish that reproduce as protogynous hermaphrodites, and maintain specific population structures (e.g. ratio of males to females, and numbers per group). These characteristics make Serranids vulnerable to capture by a number of fishing methods, and susceptible to other site-specific impacts.

Threatening Processes

The species occurs on shallow, nearshore reefs. In some areas, particularly metropolitan reefs, processes that reduce the quality of such habitat (such as reduction or change in benthic cover due to land-base discharges) may adversely affect Western Wirrah populations, but no data are available.
This site-associated reef fish species is fished recreationally, but there are no data on the effects of fishing on Western Wirrah population abundance or structure.

Research Requirements

More information is required on the distribution, relative abundance and habitats in South Australia.
Little is known of the biology or ecology of this species.

Management Requirements

Catch limits should be implemented for recreational fishing (angling, netting and spearfishing) of Western Wirrah.  
Marine protected areas are beneficial for conserving populations of large, site-associated species such as Serranids, and due consideration should be given to the formal protection of some areas (in both S.A. and W.A.) in which this species occurs.

Other Information

Western Wirrah is reported to be one of the 16 species chosen for a community-based monitoring program of abundance of nearshore fishes in W.A., between Kalbarri and Esperance (Department of Conservation and Land Management, 2003).