© 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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Warty Handfish / Verrucose Handfish

Family Name:	Brachionichthyidae
Scientific Name:	Thymichthys verrucosus (McCulloch & Waite, 1918) (formerly Sympterichthys verrucosus)
Recommended Status in S.A:	Data Deficient
Rationale:  Warty Handfish is included here because (i) it is a slow-moving, benthic fish (and therefore has a strong site association and limited mobility), and, like other members of the genus, possibly has low reproductive potential and restricted larval dispersal. These characteristics increase the vulnerability of handfishes to localised impacts, and population decline; (ii) the species is rarely recorded, and its abundance, biology, and population dynamics are unknown; (iii) Gulf St Vincent (GSV) is the type locality, and that gulf has been subject to numerous physical, chemical, biological and combined impacts during the past century since the species was first collected; and (iv) Warty Handfish are taken as bycatch in trawl and dredge fisheries, over part of the range. The few specimens known from S.A. were taken mainly by trawl (in GSV, and also in the eastern Great Australian Bight). The recommended status in S.A. is Data Deficient, due to the paucity of specimens and data. It is noted that the apparently broad depth distribution of Warty Handfish over the continental shelf, may reduce the risk that shallow-water trawling poses to this species; however localised population impacts might have occurred, and might still be occurring, but no data are available. Of particular concern is the possibility that separate, closely related species may exist over the range, which would increase the vulnerability of specific populations to impact.

Page Contents

Current Conservation Status

Pogonoski et al. (2002) suggested Data Deficient, on an Australia-wide basis.
Australian Society of Fish Biology 2001 list: Data Deficient

Distribution

Thymichthys verrucosus is found in southern New South Wales, Victoria, northern Tasmania / Bass Strait islands and South Australia (Last, in Gomon et al., 1994; Pogonoski et al., 2002; Museum of Victoria record, cited in OZCAM database, 2007).

The species may be more common and widespread than the few records suggest. It is noted that there are less than 10 museum records of this species in southern Australia (Museum of Victoria records, South Australian Museum records, CSIRO Marine Research records in the Australian National Fish collection, cited in OZCAM database, 2007).

South Australia

Southern Gulf St Vincent is the type locality (McCulloch & Waite, 1918; Eschmeyer, 2001).

In South Australia, there are museum records from southern Gulf St Vincent, including one of the type specimens (South Australian Museum record, 1905), and several specimens from near Venus Bay / Anxious Bay, in the eastern Great Australian Bight (S.A. Museum record, 1983, and unregistered specimens, 1982, cited by R. Foster, S.A. Museum, pers. comm., 2006). The species is also likely to occur in Spencer Gulf.

There is a specimen from deeper shelf waters in the Great Australian Bight, south of the S.A. / W.A. border (Last and Gledhill, 2009).

There are recreational diving records of handfish from northern Kangaroo Island (recorded by J. Thistleton, cited by Muirhead, 1997); however it is not known for this report whether the species sighted was Australian Handfish (see synopsis) or Warty Handfish.

It is noted that during a survey in 2002, a species of Brachionichthys (incorrectly reported to be the endangered Tasmanian species Spotted Handfish B. hirsutus) was recorded near the mouth of Barker Inlet (Cheshire et al., 2002). It is not known whether the species was an Australian Handfish (which, superficially, is of similar appearance to B. hirsutus), a Warty Handfish, or an undescribed species.

Habitat

Thymichthys verrucosus has been collected on the continental shelf, mostly from depths between 15m and 125m (Last, in Gomon et al., 1994; Australian National Fish Collection data, Museum of Victoria records; CSIRO Marine Research Ichthyology section records, cited in OZCAM database, 2006; Last and Gledhill, 2009) but there are specimens from deeper waters (e.g. 196m, 226m) (Pogonoski et al., 2002, citing museum data; Last and Gledhill, 2009).

Warty Handfish occurs in sheltered sand (Edgar, 2000) and shell rubble habitats, in which it is well camouflaged.

Notes on the Biology and Behaviour

Growth

Thymichthys verrucosus grows to at least 8cm (Last, in Gomon et al., 1994).

Early juveniles resemble adults in body shape (Last and Gledhill, 2009).

Diet

The species probably eats small invertebrates, such as worms, molluscs and crustaceans (Kuiter, 1996b, cited by Pogonoski et al., 2002).

Other Information

The species is small and mottled, and well camouflaged.

Thymichthys verrucosus belongs to a family of small, benthic fish with “hand-like” pectoral fins, used for walking along the sea floor.

Fisheries Information

Fishers in south-eastern Australia occasionally catch the species when dredging for scallops, in water greater than 20m (Last, in Gomon et al., 1994; Edgar, 2000). It is likely that the Warty (Verrucose) Handfish is taken as a non-target catch in the Bass Strait Central Zone Scallop (BSCZS) Fishery, but this is a widespread species and is not considered to be endangered or vulnerable (Harris and Ward, 1999, cited by AFMA, 2002f). There is little information on the amount of non-target catch taken in the BSCZS fishery, because there was no provision for recording by-catch data in logbooks until 2000. Since that time, when a revised logbook that provides for the recording of bycatch information came into use (August 2000), there has been little fishing in the BSCZS fishery (due to the fishery being over-fished previously), hence bycatch data are still lacking (AFMA, 2002f).

As is the case with other deep-water handfish species, Warty Handfish is likely to be part of the bycatch in some Commonwealth-managed trawl fisheries (Kuiter, 1996a), but there are no data available. It is noted that the species does not appear in recent Commonwealth reports of bycatch in the South East Trawl Fishery (Wayte et al., 2004) or the Great Australian Bight Trawl Fishery (Brown and Knuckey, 2002; Daley et al, 2006).

The species is recorded as part of the bycatch in the prawn trawl fishery off western Eyre Peninsula / eastern Great Australian Bight in South Australia. For example, a number of specimens have been collected from the bycatch in waters 30m – 50 deep (S.A. Museum record, 1983, and unregistered specimens from 1982, cited by R. Foster, South Australian Museum, pers. comm., 2006).

Vulnerable Characteristics of the Species

Generally, adult and juvenile handfishes are largely sedentary; these shallow-water species are known to have small, distinct and measurable populations over small ranges; they have low fecundity; they rely upon benthic structures for nesting, and have a high degree of parental care of the eggs, fully formed young at hatching (i.e. no larval phase), and poor dispersal capability. Handfishes are slow to expand their range and colonise new areas. The shallow-water species found in estuaries and associated channels are particularly vulnerable to site-specific impacts.

The strong site association, low reproductive potential and restricted larval dispersal, are characteristics that increase the vulnerability of these fishes to population decline (Pogonoski et al., 2002).

Threatening Processes

Although no critical habitats have been identified, it is likely that sandy and shelly soft-bottom substrates are important to this benthic, site-associated species. It is currently believed that all handfishes require benthic structures around which to lay their eggs (Commonwealth of Australia, 2004). Therefore, any processes (such as trawling and dredging) that degrade the quality of critical habitat for this species may impact on existing populations, and also threaten future generations of handfish, by reducing reproductive success. Bottom trawling and other commercial fishing activities may pose a threat to this species, but more information is required (Pogonoski et al., 2002). It is noted that the species has been recorded in the prawn trawling bycatch on the west coast of South Australia (e.g. South Australian Museum record F 04750, cited in OZCAM database, 2004), and also, the Warty Handfish has been previously recorded in the south-central waters of Gulf St Vincent (e.g. S.A. Museum record F 00626). In waters deeper than 10m, much of area of southern Gulf St Vincent and Investigator Strait has been trawled since the 1960s. For examples of trawl-related habitat modifications in Gulf St Vincent and/or Investigator Strait, see Drabsch (1999), SARDI Aquatic Sciences (2001), and Tanner (2003, 2005).

Research Recommendations

Data should be collated for all specimens of handfish collected or photographed in South Australia, and the specimens should be examined and identified by experts (e.g. CSIRO, Hobart).

All prawn trawl fisheries in South Australia (Gulf St Vincent, Spencer Gulf and eastern Great Australian Bight) should record the presence of any handfish species (with location and depth data) when specimens appear in bycatch. Similarly, all benthic fish trawls across the geographic range should record the presence of this, and any other handfish species.

Pogonoski et al. (2002) recommended the examination of the bycatch of scallop dredges in the Bass Strait Scallop Fishery, to determine the presence or absence of this species in its catches. This may be possible if the Bass Strait Central Zone Scallop fishery recovers, but since 2000 when logbooks to record bycatch were introduced, there has been little fishing in the BSCZS fishery in recent years (due to the fishery being over-fished previously), hence bycatch data are still lacking (AFMA, 2002f).

More information is required on the distribution and habitat of this species, across the range.

The biology, behaviour and diet of this species are unknown (Last, in Gomon et al., 1994; Pogonoski et al., 2002).

Further research on the biology and ecology of this species is required to fill data gaps (Pogonoski et al., 2002). In particular, there is little information on growth, longevity and reproduction.

Management Recommendations

Measures to reduce the bycatch of this species in benthic trawls and dredges should be encouraged.

Dredging operations (e.g. see Fairhead et al., 2002a, 2002b; Cheshire et al., 2002) should be conscious of the potential presence of handfish species, and the possible population impacts on these strongly site-associated benthic species.

Other Information

The species is rare in fish collections (Last, in Gomon et al., 1994).

There are different regional forms of Thymichthys verrucosus, which may represent separate, related species. There are broad ranges in body measurements (meristics), and there appear to be differences in body shape, skin morphology, colour, illicium shape, and size at maturity. Further material for study, and a molecular study of these populations across their ranges are needed to determine their relationships (Last and Gledhill, 2009).

Support for S.A. Listing

Graham Edgar (University of Tasmania), and Barry Hutchins (ex-WA Museum), both recommending Data Deficient category.