© 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.

---

 Western Sea Carp

Family Name:	Aplodactylidae
Scientific Name:	Aplodactylus westralis Russell, 1987
Recommended Status in S.A:	Least Concern (in S.A.)
Rationale:  The Western Sea Carp is included here because it (i) is found over a relatively narrow depth range in shallow continental shelf waters in S.A. and W.A., and is more numerous in W.A.; (ii) it is a sedentary, site-associated reef fish that relies upon macroalgae-covered reefs for feeding, shelter and presumably other aspects of the life cycle, and these characteristics may render populations vulnerable to direct impacts (fishing mortality) or indirect impacts (due to habitat loss). However, the suggested status is Least Concern for South Australia, because there is little evidence of habitat degradation in many of the areas in S.A. where this species has been recorded, and other threats, such as fishing mortality, are assumed to be minor. Over the geographic range, it is likely that the species is most frequently caught in W.A., where it is part of the discarded bycatch of commercial gillnet fishing, and is also caught recreationally. There is some evidence that fully protected marine reserves can benefit populations of fishes with strong habitat association, such as the related Southern Sea Carp, and it is likely that such reserves would also benefit populations of Western Sea Carp.

Page Contents

Current Conservation Status

No listings known

Distribution

Southern Australia

A. westralis is found in S.A. and W.A., and is considered to be more numerous in the latter State, particularly the south coast of W.A. (Hutchins and Swainston, 1986). Rottnest I. is the western geographical limit (Hutchins and Swainston, 1986, 2001).  In southwestern Australia, the species has been recorded occasionally on reefs at the Recherche Archipelago, and Israelite Bay, and rarely on reefs in mainland bays (Hutchins, 2005).

South Australia

In S.A., the species is found mainly in the western part of the State, but there are records from at least as far east as lower Fleurieu Peninsula. Examples of locations in S.A. where A. westralis has been recorded include Anxious Bay on the west coast; Redbanks and Wanna (southern Eyre Peninsula); Stenhouse Bay, Howling Cave Bay I. and other locations along southern Yorke Peninsula; Althorpe I. (near western Investigator Strait); Hanson Bay and Point Tinline (southern Kangaroo I.), and Cape Jervis (lower Fleurieu Peninsula) (Hutchins and Swainston, 1986; Russell, 1987; S. Shepherd, unpubl. data, 2002, 2004; S. Shepherd and J. Brook, unpubl. data, 2002; S. Shepherd, J. Brook and J. Scott, unpubl. data, 2004; S. Shepherd, M. Kinloch and H. Bartram, unpubl. data, 2004).

Habitat

The species occurs on shallow, wave- and surge-exposed, coastal rocky reefs with abundant macroalgae (Hutchins and Swainston, 1986; Edgar, 2000). Depth range is about 0m – 20m (Russell, 1987; Edgar, 2000).

Notes on the Biology

Growth

Grows to 63cm (Kuiter, 1993; Edgar, 2000) or 69 cm (Hutchins and Swainston, 2001).
Maximum-recorded weight is 4.564kg (Hutchins and Swainston, 1986; Australian Underwater Federation, 2003).

Diet

Sea Carps feed on macroalgae ripped from the substrate by strong surge or currents (Kuiter, 1996a). According to Edgar (2000) A. westralis feeds on/in brown macroalgae.

Fisheries Information

Commercial

Generally, the species is not targeted commercially because the flesh has an unpleasant smell.
Western Sea Carp is a minor discarded bycatch species in the W.A. temperate demersal gillnet and demersal long-line fisheries, with low numbers recorded (e.g. McAuley and Simpfendorfer, 2003).

Recreational

Some spear fishers take Western Sea Carp. It is noted that the record sized specimen (4.564kg) was taken by spearfishing at Rottnest Island in W.A. (Hutchins and Swainston, 1986; Australian Underwater Federation Inc., 2003).
Some anglers take the species. Some clubs and associations keep records of the maximum sizes caught, such as 3.155kg, a specimen of national record, taken in Windy Harbour in WA in 1995 (e.g. Australian Anglers Association, 2005), and 2.196kg (the Lancelin Angling and Aquatic Club record, being a specimen taken in 1988).

Vulnerable Characteristics of the Species, and Threatening Processes

The Western Sea Carp is a found over a relatively narrow depth range (0m - ~ 20m) in shallow continental shelf waters.
Western Sea Carp is a benthic, sedentary fish with poor swimming ability, and such characteristics can render populations vulnerable to exploitation.
The species is associated with shallow, macroalgae-covered reefs, particularly kelp. Western Sea Carp relies upon such macroalgae-covered habitats for feeding, shelter and presumably also reproduction. Any processes (e.g. such as nutrient pollution and sedimentation from coastal discharges, physical damage and sedimentation from dredging, channel clearing etc), which reduce the cover of large macroalgae in nearshore areas, may adversely affect populations of this species; however there are no specific data.
Mortality from bycatch in commercial fishing nets (and also mortality due to angling and spear-fishing) may be a threat to Western Sea Carp populations in some areas, but more data are required.

Research Requirements

More information is required on the relative abundance of this species in some parts of the geographic range, including most parts of South Australia.
There is little information on reproduction in this species.
Potential impacts of nearshore reef degradation on species such as Sea Carp (that rely upon macroalgae-rich habitats) should be investigated.

Management Requirements

Recreational catch limits should be introduced for site-associated reef fish species, including Western Sea Carp.
Plans for marine protected areas in S.A. should give due consideration to site-associated reef fish species such as the Sea Carps. It is noted that, during a netting survey in the Governor Island Marine Reserve in Tasmania (Murphy and Lyle, 1999), the numbers and total weight of the related species Southern Sea Carp caught inside the reserve were more than double those from outside the reserve.