© 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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Rigid Boxfish

Family Name:	Aracanidae (or Ostraciidae, sub-family Aracaninae)
Scientific Name:	Caprichthys gymnura McCulloch and Waite, 1915
Recommended Status in S.A:	Data Deficient
Rationale:  Included here because (i) the species is endemic to southern W.A. and western S.A., and the west coast of S.A. appears to be the eastern edge of the range; therefore the Rigid Boxfish has a limited distribution in South Australia; (ii) generally, temperate boxfishes are strongly site-associated / territorial and haremic, characteristics that can increase the vulnerability of populations to localised impacts; (iii) the species is part of the bycatch of trawl fishing in the Great Australian Bight, and trawl-caught specimens are unlikely to survive capture; and (iii) there is little existing information about the biology, population dynamics, or relative abundance of this species across its range.

Page Contents

Current Conservation Status

No listings known

Distribution

Hutchins and Swainston (1986) and Kuiter (in Gomon et al., 1994) reported the distribution as ranging from the Great Australian Bight in S.A., to Geraldton in W.A.
Most museum specimens are from W.A. (Australian Museum records, National Fish Collection records, South Australian Museum record, Museum of Victoria record, cited in OZCAM database, 2007).
There is a paucity of records from South Australia. In S.A., the species is known from parts of the Great Australian Bight, including deeper waters off the western region of the Bight, near the S.A. / W.A. border (Hutchins and Swainston, 1986; Kuiter, in Gomon et al., 1994; Museum of Victoria record, cited in OZCAM database, 2007).

Habitat

This species is found from shallow to deep waters on the continental shelf, and the reported depth range is 1m – 200m (Kuiter, in Gomon et al., 1994). There is little published information about the habitat of the Rigid Boxfish, which is mostly observed in trawl catches in the Great Australian Bight.
The species has occasionally been observed in tide pools along the south coast of W.A., perhaps washed ashore by storms (Hutchins and Swainston, 1986; Kuiter, in Gomon et al., 1994).
The species has also been recorded in estuaries in southwestern W.A. (Potter et al., 1990). During a fish survey at Israelite Bay (south-western W.A.), C. gymnura was recorded rarely (i.e. a single specimen) in reef habitat, 1-3m (Hutchins, 2005; B. Hutchins, W.A. Museum, pers. comm., 2007). The species has also been recorded in other habitat (e.g. collected by trawl / dredge at the Recherche Archipelago, in soft bottom habitat) (Hutchins, 2005).

Notes on the Biology and Behaviour

Growth

This small species grows to around 11cm (May and Maxwell, 1986, cited in Froese and Pauly, 2007), 12cm (Kuiter, in Gomon et al., 1994) or 14cm (Hutchins and Swainston, 1986).

Diet

In general, boxfishes are benthic feeders (Kuiter, 1996a) that eat small sessile invertebrates, and algae (Nelson, 1994, cited in Froese and Pauly, 2007).

Reproduction

According to Kuiter (2000), temperate boxfishes are protogynous hermaphrodites, and when in captivity, females of some species in the Aracanidae have been observed transforming into males.

Other Notes on the Biology

The males and females are both creamy white to yellowish tan in colour, but differ in markings. Males have heavy, wavy, longitudinal lines on the back and caudal peduncle, and black spots on the belly. Females have fine black spots on the sides, near the spine bases (Hutchins and Swainston, 1986; Kuiter, in Gomon et al., 1994; Kuiter, 1996a).

Fisheries Information

The Rigid Boxfish is taken as bycatch by trawlers in the Great Australian Bight (GAB) (Hutchins and Swainston, 1986; Kuiter, in Gomon et al., 1994). Bycatch data are not available for this report, and it is noted that Rigid Boxfish was not recorded during trawl bycatch sampling in 2000-2001 in the GAB (see Brown and Knuckey, 2002).

Vulnerable Characteristics of the Species

The species appears to have a very limited distribution within South Australia, and the western Great Australian Bight may be the eastern edge of the species range.
In general, boxfishes are territorial, haremic, site-associated fish species, characteristics that can increase their vulnerability to site-specific impacts.

Threatening Processes

Threatening processes are not well known for this species. Trawling (e.g. in the Great Australian Bight) is a recorded source of mortality, but the extent to which capture in trawls may affect Rigid Boxfish populations is not known.

Research and Management Requirements

More information is required on the distribution (particularly in western South Australia) and relative abundance of this species.
There is virtually no information on the habitat of the Rigid Boxfish in deeper waters, where most specimens have been recorded. The life history is not well known, and information on the habitat, habits, biology and population dynamics of Rigid Boxfish may also assist in managing potential impacts on this species, such as bycatch in trawlers.