© 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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Western Roughy

Family Name:	Trachichthyidae
Scientific Name:	Optivus agrammus Gomon, 2004
Recommended Status in S.A:	Data Deficient
Rationale:  The species is included here because (i) the Western Roughy has a limited known geographical distribution in S.A. (mainly western part of the State); (ii) the biology has not been investigated, and also, there appears to be no knowledge of the population sizes, population dynamics or habitat requirements of Western Roughy; (iii) the species may be vulnerable to trawl capture in the Great Australian Bight, but data are lacking, and more information is required.

Page Contents

Current Conservation Status

No listings known

Distribution

The Western Roughy is known mainly from western South Australia (deeper waters off Venus Bay, and various locations throughout the Great Australian Bight), through to Fremantle in W.A. (Gomon, in Gomon et al., 1994; Edgar, 2000; Gomon, 2004). there is one record from southern Spencer Gulf, reported to be this species (Currie and Sorokin, 2010).
The holotype comes from the central Great Australian Bight (Gomon, 2004).
Many of the South Australian records are trawl-caught specimens from the Great Australian Bight (CSIRO Marine Research data, cited in Gomon, 2004 and CSIRO, 2007). An example of a museum specimen from S.A. is one from 6 miles (9.6 km) off Venus Bay (Museum of Victoria data).

Habitat

The species has been recorded from coastal waters on the continental shelf and upper continental slope, between 40m and 320m (Gomon, 2004).
The habitat of the Western Roughy has not been recorded. A related species found in south-eastern Australia, the Slender Roughy or Violet Roughy O. agastos (formerly misidentified as the New Zealand species O. elongatus), is found in clear waters near rocky reefs and ledges, both nearshore and offshore (Kuiter, 1996a).

Notes on the Biology

Maximum size is reported to be at least 12cm (Gomon, in Gomon et al., 1994).
Virtually nothing is known about the biology of this species; however a related species from New Zealand, O. elongatus, is nocturnally active, and inhabits cracks and crevices during the day. O. elongatus feeds on small mobile benthic organisms (Russell, 1983), and the diet of O. agrammus is likely to be similar.

Fisheries Information

Most records of this species come from trawl surveys in the Great Australian Bight. Given the depth distribution, it is possible that the species is part of the discarded bycatch in the S.A. West Coast Prawn Trawl fishery, and the Great Australian Bight Trawl Fishery, but no data are available for this report. It is noted that Optivus agrammus (or Optivus sp.) was not recorded during a scientific monitoring program of bycatch in the GAB trawl fishery, during 2000 and 2001 (Brown and Knuckey, 2002).

Vulnerable Characteristics of the Species, and Threatening Processes

The species has a relatively small geographic distribution (south-western Australia), and its presence in South Australia appears to be limited to the western part of the State (i.e. Great Australian Bight).
Trawling may be a threatening process, but data are lacking, and more species-specific information is required. It is noted that the related south-eastern Australian species of Optivus is frequently caught in prawn trawls and fish trawls in New South Wales. Although it is considered to be of relatively “high resilience”, due to having a broad depth range, and pelagic eggs and larvae (N.S.W. Department of Primary Industries, 2004), the south-eastern Optivus species is reported to suffer barotrauma when caught in bycatch, and is classified as a species of “high fisheries impact potential”, and at “intermediate to high” risk of population impacts from trawl fishing (N.S.W. Department of Primary Industries, 2004).

Research and Management Requirements

More information is required on the habitat requirements, biology and population dynamics of this species.
Data are required on the potential population impacts of mortality due to trawl capture.
Quantification over space and time is required for bycatch in the S.A. West Coast Prawn Trawl Fishery (and in the Spencer Gulf Prawn Trawl fishery), and measures to reduce the bycatch of finfish species should be introduced (as has occurred in the Spencer Gulf Prawn Trawl fishery in S.A.).