© 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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Australian Tusk

Family Name:	Ophidiidae
Scientific Name:	Dannevigia tusca Whitley, 1941
Recommended Status in S.A:	Data Deficient
Rationale:  The Australian Tusk is included here because (i) it is a benthic fish species in lower continental shelf and upper slope waters, and is susceptible to capture by trawls and demersal long-lines; (ii) it may have a relatively low resilience to fishing pressure, as indicated by preliminary risk assessments; (iii) there is a paucity of information on the habitat requirements and ecology of this species, and the effects of trawling in the deeper continental shelf and upper slope waters in which D. tusca occurs;  and (iii) very little is known of the biology or population dynamics of Australian Tusk, and here has been insufficient assessment of the sustainability of fishing, particularly the impacts of trawling and demersal long-lining on Australian Tusk populations.

Page Contents

Current Conservation Status

No listings known

Distribution

Southern Australia

The Australian Tusk is considered to be a common species (Nielsen et al., 1999), ranging from western Bass Strait in Victoria, through the Great Australian Bight, to just north of Geraldton in W.A. (Daley et al., 1998).
The type locality is southwest from Eucla, Great Australian Bight, W.A. (Eschmeyer, 2001).
The species is considered to be more common in the Great Australian Bight than at the edges of the range.

South Australia

Examples of locations in South Australia where the species occurs include the deeper waters of the continental shelf in the Great Australian Bight (GAB); deeper waters off western Eyre Peninsula (south-eastern GAB); deeper (continental slope) waters south-east of Kangaroo Island and west of Cape Jaffa; and deeper (continental slope) waters off Port MacDonnell in the lower South-East (Brown and Knuckey, 2002; CSIRO Marine Research records, cited in CSIRO, 2005; Australian Museum records, Museum of Victoria record, cited in OZCAM database, 2006).

Habitat

The Australian Tusk is found in benthic habitats on the outer continental shelf and upper slope (Daley et al., 1998), but occasionally is found in shallower waters (Hutchins and Swainston, 1986).
The reported depth range is about 130m – 420m (Daley et al., 1998) or 115m – 400m (Nielsen et al., 1999). CSIRO Marine Research, Museum Victoria, Australian Museum, and New South Wales Fisheries (2001) reported that the maximum depth is about 520m, and that the species is commonly recorded in the 300m – 400m depth range.
The habitat at the type locality for this species was the edge of a submarine bank in the Great Australian Bight (Eschmeyer, 2001).

Notes on the Biology

Growth and Age

Australian Tusk grows to about 56cm (May and Maxwell, 1986; Gomon, in Gomon et al., 1994) but is more commonly observed at less than 50cm (Daley et al., 1998).
Australian Tusk grows to more than 1kg in weight (Daley et al., 1998).
The record size is 1.02kg, being a specimen taken by recreational fishing in Yallingup, W.A., in 1971 (Hutchins and Swainston, 1986; Australian Anglers Association, W.A. Division, 2002a).
It is possible that the species is long-lived (e.g. 20 years or more), like other members of the family (e.g. see Nielsen et al., 1999, for G. blacodes).

Reproduction

Members of the family Ophidiidae are oviparous, with pelagic larvae. There is no special larval stage (Nielsen et al., 1999).

Fisheries Information

Commercial

When taken outside of 3 nautical miles (NM) from the coast, catches of Australian Tusk are managed by the Commonwealth (and when taken inside 3 NM, are managed by the States) (AFMA, 2002a).
Australian Tusk is caught in small commercial quantities in Commonwealth-managed fisheries, mainly off South Australia (Daley et al., 1998; Nielsen et al., 1999). Fish from the Great Australian Bight are marketed as Tusk in southern Australian markets (Seafood Services Australia, 2003), and are promoted as a substitute for Ling.
According to statistics from BRS’s National Fisheries Production Database (NFPD) (BRS, 2004a), the highest total catches of Australian Tusk during the 1990s were 5t in 1991/92 and 3t in 1996/97, with 0 or 1t catch in most other years. As discussed below, the majority of the Australian catch comes from the Great Australian Bight.
D. tusca is a minor component of the catch in the Great Australian Bight Trawl Fishery (GABTF), yet it is from this fishery that the majority of the total annual catch from southern Australia is taken. Reported catches in recent years are shown (Table 21).

Table 21 Australian Tusk: Reported Catch in the GABTF, 1995 – 2002
Year	Catch (t)
1995	3
1996	1
1997	2
1998	2
1999	2
2000	1
2001	3
2002	2
(from Lynch and Garvey, 2003)

Bycatch sampling in the GAB during the early 2000s recorded lower numbers than in the reported catch for the fishery during that period. For example, sampling of the GABTF during 2000 and 2001 showed that during the survey period, D. tusca was recorded in 33 of the 209 trawl shots. The average quantity retained was 2kg per trawl shot, and the average quantity discarded was 0.3kg per shot. During a pilot survey program, about 94% of the Australian Tusk bycatch in the GABTF was retained (Brown and Knuckey, 2002; AFMA, 2002a).
D. tusca is part of the bycatch in the Commonwealth-managed SESSF (AFMA, 2002a). In 2000/01, fishers’ logbooks for the South East Trawl Fishery (SETF) recorded a bycatch of about 450kg of Australian Tusk, and a monitoring program during the same period reported that approximately half of the catch was retained (AFMA, 2002a). Wayte et al. (2004) reported that in the otter trawl sub-fishery of the Commonwealth-managed South East Trawl Fishery (SETF), an Integrated Scientific Monitoring Program (ISMP) recorded, in 49 trawl shots: 140kg of Australian Tusk retained, and 85kg discarded. In the Danish seine sub-fishery of the SEFT, the ISMP recorded only 2kg of Australian Tusk discarded in 7 shots (Wayte et al., 2004).
The species is taken mainly by trawl; however there is a concession which permits the use of fish hooks, shark hooks, and gillnets to be used to catch Australian Tusk in Commonwealth-managed waters (outside 3NM), with no catch limits (AFMA, 2004e).  The species is listed as part of the retained by-product in the Scalefish Demersal Longline sub-fishery and the Scalefish Automatic Longline sub-fishery of the Commonwealth-managed Gillnet, Hook and Trap fishery (Webb et al., 2004; Bromhead and Bolton, 2005). In this fishery, an Integrated Scientific Monitoring Program recorded a retained catch of about 222kg (plus 2kg discarded) of Australian Tusk in 9 long-line shots.
There are also commercial fishing records from the Bass Strait region (Anonymous, 2002b).
Australian Tusk is also a minor retained by-product species in the Western Australian trawl fisheries (AFMA, 2004f; Bromhead and Bolton, 2005). In the Western Deepwater Trawl Fishery (WDTF), which operates between 300m and 600m deep in waters south of 26⁰S (AFMA, 2004f), “catch volumes” of Australian Tusk in the WDTF, according to fishers’ logbooks, have included 182 in 1993/94, 83 in 2001/02, and approximately 60 in 2002/03 (AFMA, 2004f). Therefore, a total catch of ~ 325 Australian Tusk specimens was reported for the period 1992 – 2003 (AFMA, 2004f), but it is not known for this report whether the data from logbooks accurately reflects the total catch, or is underestimated.

Recreational

The species is very occasionally taken in shallower waters by anglers (Hutchins and Swainston, 1986), and some organisations keep records of the maximum sizes caught (e.g. Australian Anglers Association, W.A. Division).

Vulnerable Characteristics of the Species

In a draft ecological risk assessment of the South East Trawl and Danish Seine Fishery (Wayte et al., 2004), 5 “productivity attributes” and 5 “attributes of susceptibility” for Dannevigia tusca were used to categorise it as a “medium risk” species; i.e. susceptible to population impacts from trawling. In a similar report for the Great Australian Bight Trawl Fishery, Daley et al. (2006) reported that Pink Ling is in a “high risk” category in terms of population impacts from the operation of the fishery, and that 13t were caught during the Integrated Scientific Monitoring Program Assessment period (from end of 1990s to mid 2000s). Previously, Froese and Pauly (2004) reported the Australian Tusk to have a low resilience to exploitation in terms of minimum population doubling time (based on preliminary age and growth estimates). The assumed level of resilience has since been changed to “medium”, with “moderate to high vulnerability” (Froese and Pauly, 2007), and the vulnerability of populations of fish in Ophidiidae to over-exploitation is noted here.
Adults are site-associated on deep reefs and other underwater features, and are thus vulnerable to capture by fishers.

Threatening Processes

Fishing is likely to be the main threatening process. There has been little assessment of the effects of fishing on this species; however a recent draft ecological risk assessment report for the South East Trawl Fishery, listed D. tusca as being a “medium risk” species, in terms of population impacts from trawling (Wayte et al. 2004). A similar report also ranked the species as being of “medium risk” of impact from capture in the Scalefish Demersal Longline sector of the Commonwealth-managed Gillnet, Hook and Trap Fishery (Webb et al., 2004).

Research Requirements

There is a paucity of information on the habitat requirements of the species in continental shelf and slope waters, and the effects of trawling such habitats.
There is a lack of data on the biology and population dynamics (including longevity, reproduction and recruitment strength).

Management Requirements

An assessment of the sustainability of fishing this species is required, particularly the impacts of trawling and demersal long-lining on Australian Tusk populations.
Catch restrictions are required, pending an assessment of stock status. Given the relatively low numbers caught per annum, it is possible that the species is naturally of lower abundance than related species, such as Pink Ling.

Other Information

Pink Ling is found in the Murray Canyons region, off south-eastern South Australia (AFMA, 2006f), part of which has become a Commonwealth-managed marine protected area.