© 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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Castelnau’s Wrasse / Pretty Polly

Family Name:	Labridae
Scientific Name:	Dotalabrus aurantiacus (Castelnau, 1872)
Recommended Status in S.A:	Data Deficient, possibly Least Concern
Rationale:  Although Castelnau’s Wrasse has a broad geographic range across southern Australia, and appears to be relatively common in some parts of the range, it is included here because (i) it is a site-associated Labrid, and members of the family are intrinsically vulnerable due to their strong habitat association, and demography / life history characteristics; (ii) it occurs over a relatively narrow depth range in upper continental shelf waters; (iii) the species is territorial and strongly site-associated within nearshore habitats, in the vicinity of seagrass and macroalgae.  In some parts of its range, such habitats are subject to damaging processes, such as eutrophication from sewage and wastewater discharges, sedimentation, and physical damage from dredging and near-shore developments, amongst other impacts. The status of the species cannot easily be determined due to lack of data on population sizes around the State; lack of data on the biology and life history characteristics of the species; and lack of data on the extent of threatening processes over the range. In S.A., the species may possibly qualify for a status of Least Concern, due to its broad distribution and relative commonness, coupled with the fact that it is not targeted in fisheries in S.A., and there is currently no evidence of population decline.  The specific impacts of nearshore habitat degradation on site-associated species such as wrasses should be investigated.

Page Contents

Current Conservation Status

No listings known

Distribution

Southern Australia

Castelnau’s Wrasse is found across the southern half of Australia, between N.S.W. and approximately Rottnest Island in Western Australia, and the distribution includes northern and eastern Tasmania (Hutchins and Swainston, 1986, 2001; Edgar, 2000; Barrett and Wilcox, 2001).
Castelnau’s Wrasse is commonly encountered on reefs in Victoria (Edmunds and Hart, 2003).

South Australia

Castelnau’s Wrasse is widespread in S.A., with numerous museum and survey records, ranging from Encounter Bay through to the Great Australian Bight. Examples of locations where the species has been recorded include Encounter Bay; many sites along the Fleurieu Peninsula; the northern, central and southern metropolitan coast of Gulf St Vincent; north-western, northern and north-eastern Kangaroo I.; coastal mainland reefs and islands off the western “toe” of Yorke Peninsula / western Investigator Strait (including Chinaman’s Hat I., Haystack I., the Althorpe group and the Western Is.); mid-western Spencer Gulf; south-eastern and south-western Spencer Gulf (with many records from the Thorny Passage area); southern Eyre Peninsula (western and eastern sides); Investigator group of islands and Nuyts Archipelago (Kuiter, 1983; Branden et al., 1986; K. Branden and S. Shepherd, unpubl. data, 1987; MLSSA, 1997 and undated; S. Shepherd, J. Brook, J. Baker and K. Smith, unpubl. data, 2002; Fairhead et al., 2002b; photo by E. Schlögl, 2003, cited in Australian Museum, 2006b; Shepherd and Brook, 2003b; S. Shepherd, B. Parkhurst, A. Bloomfield, J. Brook, K. Smith, J. Scott, unpubl. data, 2004; data by G. Edgar and N. Barrett, cited in Shepherd et al., 2005; S. Shepherd, unpubl. data, 2006; Edgar et al., 2006; Australian Museum, Museum of Victoria and S.A. Museum records, cited in OZCAM database, 2006).

Habitat

The published depth range is 1m – 47m (Edgar, 2000).
Castelnau’s Wrasse is found in seagrass beds (e.g. Amphibolis and Posidonia), and on macroalgae-covered rocky reefs (Hutchins and Swainston, 1986, 2001; Kuiter, 1996a; Jordan et al., 1998; MLSSA, undated; Australian Museum, 2006b).
During a survey in 2002 of the reef fish fauna of the St Francis Isles in the Nuyts Archipelago, Castelnau’s Wrasse were recorded on both relatively sheltered and wave exposed reefs (Shepherd and Brook, 2003b).
During a recent survey of nearshore fish habitats in south-western Australia, Castelnau’s Wrasse was recorded in seagrass beds of medium density; also on reefs with macroalgae cover of medium density, and on granite reefs deeper than 30m, characterised by a sparse cover of macroalgae or sponges (Harvey et al., 2004).
In Tasmania, juveniles have been recorded in estuarine areas (e.g. Tamar River), in the vicinity of Posidonia seagrass (Jordan et al., 1998). The species has also been recorded in bare sand habitats, near seagrass (Jordan et al., 1998).
Castelnau’s Wrasse has also been recorded on artificial reefs (e.g. shipwrecks) (MLSSA, 1999a).

Notes on the Biology

Growth

The previously published maximum size for Castelnau’s Wrasse was 15cm (Hutchins and Swainston, 1986; Edgar, 2000); however it is noted that during a survey in 2002 at Nuyts Archipelago in western S.A., average size of observed specimens was ~ 18.3cm (SE 1.2) (Shepherd and Brook, 2003b).

Diet

The species is described as a benthic carnivore (Shepherd and Brook, 2003b).

Other Information

Castelnau’s Wrasse is sexually dimorphic (Australian Museum, 2006b).
The appearance of the species is extremely variable between habitats (Kuiter, 1996a).
Castelnau’s Wrasse moves by bobbing up and down at an oblique angle, with the head up and tail down (Australian Museum, 2006b).

Fisheries Information

Commercial

The species is not targeted commercially.
In Tasmania, under the Tasmanian Fisheries (Scalefish) Rules 2004, Regulation 100, there is a commercial fishing possession limitation of a maximum of 3 Castelnau’s Wrasse per licence holder per day, due to the development of a separate aquarium market for small wrasse species. For this species, catch statistics for the aquarium market are not available for this report.
The species is a minor bycatch species in the Bass Strait scallop fishery (Haddon and Semmens, 2002).

Recreational

The species is taken by spear fishers in some areas. Castelnau’s Wrasse was one of the species caught in spearfishing competitions in South Australia during the 1980s (Johnson, 1985b).
During the National Recreational and Indigenous Fishing Survey (Henry and Lyle, 2003; SARDI data, September, 2005), recreational catches of wrasses in S.A. were not recorded at species level. The proportion of the total catch that is Castelnau’s Wrasse is assumed to be low compared with the catch of larger, edible species of wrasse.

Vulnerable Characteristics of the Species and Threatening Processes

As is the case with other temperate Labrids, Castelnau’s Wrasse has a number of characteristics that make the species vulnerable to over-exploitation, and population decline. The species is strongly site-associated within nearshore habitats, in the vicinity of seagrass and macroalgae.  In some parts of its range, such habitats in which this species occurs are subject to damaging processes, such as eutrophication from sewage and wastewater discharges, sedimentation, and physical damage from dredging and near-shore developments, amongst other impacts (e.g. for Gulf St Vincent in S.A., see Shepherd, 1970; Shepherd et al., 1989; Cheshire et al., 1998; Cheshire and Westphalen, 2000; Turner and Cheshire, 2002; Fairhead et al., 2002b; Baker, 2004; Westphalen et al., 2005).
No information on the mode of reproduction in this species could be found, for this report. If Castelnau’s Wrasse is a protogynous hermaphrodite, as are many of the other sexually dimorphic Labrids in temperate Australia, then this characteristic may increase the vulnerability of fished populations to decline. The species is known to be taken by spear fishers, and possibly by anglers, but no species-specific data are available on the numbers taken, nor of the impacts of fishing on this site-associated species.

Research Requirements

There is a lack of data on the (i) populations sizes within the range (including South Australia); (ii) the biology (e.g. age / longevity, growth, reproduction) life history characteristics and population dynamics of the species; and (iii) the specific impacts of nearshore habitat degradation on site-associated species such as wrasses.

Management Requirements

Ongoing control of impacts that reduce the quality and cover of nearshore reef and seagrass habitats.
Plans for marine protected areas in S.A. should give due consideration to the declaration of nearshore sanctuary zones that include such site-associated species as Castelnau’s Wrasse.

Other Information

The species is known to occur in a number of marine parks and sanctuaries in Victoria, such as Bunurong, Port Phillip Heads, Phillip I., and Wilsons Promontory (Edmunds et al., 2003; Plummer et al., 2003; Hart et al., 2005).