© 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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Silver Spot

Family Name:	Chironemidae
Scientific Name:	Threpterius maculosus Richardson, 1850
Recommended Status in S.A:	Data Deficient
Rationale:  Although the Silver Spot has a broad geographic range across southern Australia, it is included here because (i) it is a site-associated reef fish found over a limited depth range in shallow continental shelf waters, which may increase its vulnerability to localised reef impacts in some areas; (ii) it is a minor bycatch species of rock lobster fishing and prawn trawling, and is also occasionally taken by recreational fishers (anglers and spear fishers), but there are few data on fishing mortality, and no comment can be made about potential population impacts, partly due to the paucity of data on abundance; and (iii) information is lacking on population sizes / relative abundance, biology and populations dynamics of this species across the range.

Page Contents

Current Conservation Status

No listings known

Distribution

Southern Australia and New Zealand

Silver Spot is broadly distributed across southern Australia, from southern N.S.W. through to southern W.A., including Tasmania (Hutchins and Swainston, 1986).
The species is considered to occur “rather commonly” in the central portion of the range (Kuiter, in Gomon et al., 1994).
Silver Spot has also been recorded in New Zealand (Paulin et al., 1989, cited in Froese and Pauly, 2007).

South Australia

Examples of locations in S.A. where Silver Spot has been recorded include the Investigator Group islands in the eastern Great Australian Bight; Greenly Island, and another location seaward of Coffin Bay (off Eyre Peninsula); Memory Cove and another location south of the Port Lincoln coastal area (south-western Spencer Gulf); eastern Spencer Gulf (e.g. Moonta area); Marion Bay and other locations in western Investigator Strait, off the “toes” of Yorke Peninsula; other locations in Investigator Strait (e.g. off Point Marsden, northern Kangaroo I.); Troubridge Point and other locations off the “heel” of Yorke Peninsula; north-western Kangaroo I. (e.g. Cape Borda and Cape Torrens); north-eastern Kangaroo I. (e.g. Rocky Point near Eastern Cove); eastern Kangaroo I. (Antechamber Bay); southern Kangaroo I.; south-eastern Gulf St Vincent and Fleurieu Peninsula (e.g. Sellicks; Port Willunga, Second Valley, Cape Jervis); off Tunkalilla and Waitpinga; in Encounter Bay (Port Elliot), and the lower South East (e.g. off Cape Northumberland) (Reynolds, 2003a; D. Muirhead, unpubl. data, 2006; Australian Museum records, Museum of Victoria records, South Australian Museum records, cited in OZCAM database, 2007).
Although the species is not commonly seen by divers, it is noted that, collectively, there are at least 28 South Australian records of this species in southern Australian museums (Australian Museum records, South Australian Museum records, cited in OZCAM database, 2007).

Habitat

Silver Spot is found on shallow rocky reefs with dense cover of macroalgae (Kuiter, 1993, cited in Froese and Pauly, 2007; Kuiter, in Gomon et al., 1994; Harvey et al., 2004). The habitat is also described as “shallow reef and weed areas” (Hutchins and Swainston, 1986).
In south-western Australia, T. maculosus has been recorded from reefs and seagrass beds (Hutchins, 2005).
The species is found from intertidal (e.g. S.A. Museum record F 02926; specimen from a rock pool) down to at least 33m deep (Museum of Victoria record A 14218, cited in OZCAM database, 2007). Although most specimens have been recorded from less than 30m deep, it is noted that CSIRO Marine Research (record C 2265, cited in OZCAM database, 2007) has a record of T. maculosus from 72m deep (west of Garden I., W.A.)

Notes on the Biology

Silver Spot grows to between 35cm (Kuiter, 1993) and 40cm (Hutchins and Swainston, 1986, 2001).
The recorded maximum weight of a T. maculosus specimen is 1.389kg (Hutchins and Swainston, 1986), being a specimen taken by spearfishing in Victoria (Australian Underwater Federation Inc., 2003). Another record size is a specimen of 1.1kg, taken by angling (Australian Anglers Association – W.A. Division, 2002a).

Fisheries Information

Commercial

Silver Spot is a minor bycatch species in the South Australian Rock Lobster fishery (Sloan, 2003a). Based on a 1% sub-sample of the bycatch, during which 3 T. maculosus individuals were caught in the Northern Zone (Brock et al., 2004), the annual catch in that zone may be as high as 300 specimens.
There are records of the species in the bycatch of prawn trawling in Investigator Strait (South Australian Museum record F 06240, cited in OZCAM database, 2007).

Recreational

There are records of Silver Spot being taken by spear fishers. The Australian record sized specimen was caught by spearfishing (Hutchins and Swainston, 1986; Australian Underwater Federation Inc., 2003).
Silver Spot is taken by some anglers, and there are isolated records from all States in which the species occurs. Some clubs and associations keep records of the maximum sizes caught (e.g. Australian Anglers Association Inc. - W.A. Division, 2002a; Australian Anglers Association - Victorian Division, 2003; New South Wales Fishing Clubs Association, 2003).

Vulnerable Characteristics of the Species, and Threatening Processes

Silver Spot is site-associated on shallow subtidal reefs (and has also been found in seagrass beds), and has a small depth range. These characteristics could increase the vulnerability of the species to localised impacts, particularly in habitats close to metropolitan centres, and in other areas with high levels of land-based impact (e.g. see examples of reef degradation in Gulf St Vincent, in synopsis on Western Kelpfish).
Generally, fishing is considered to be a threatening process for populations of site-associated reef fish which occur over a limited depth range; however there are no specific data on the effects of fishing on Silver Spot populations.

Research Requirements

There is little information on the relative abundance of Silver Spot across its known geographic range. Data are also lacking on the biology, habits, habitat preferences, and population dynamics of this species.
The bycatch of Silver Spot in various coastal fisheries should be quantified.
There is some recent information on bycatch of this species in the S.A. Rock Lobster Fishery, and is has also been recorded in the bycatch of prawn trawlers. If possible, Silver Spot bycatch in these fisheries should continue to be recorded over space and time (and see Management Requirementsbelow).

Management Requirements

In rock lobster fisheries and prawn trawl fisheries, methods are required, where possible, to reduce the bycatch of benthic fish species such as Silver Spot. During the past decade, examples of various developments in the Gulf St Vincent and Spencer Gulf prawn trawl fisheries to reduce bycatch are provided by Carrick (1997), MacDonald (1998), Broadhurst et al. (1999, 2000), PIRSA (2003), and Svane (2004). For the Rock Lobster fishery in S.A., Sloan (2003a) and Australian Government Department of the Environment and Heritage (2003d) discussed the benefits of using “escape gaps” in rock lobster pots (to reduce the bycatch of non-target species), and the voluntary use of such pots with escape gaps, within the Northern Zone of the fishery.
Recreational fishing restrictions (angling and spear fishing) are required for site-associated nearshore reef fish species such as Silver Spot.
Ongoing control of impacts that reduce the quality and cover of nearshore reef and seagrass habitats, particularly in metropolitan areas.
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 Silver Spot.