© 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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Little Conger Eel, Largepore Conger Eel and Umbrella Conger Eel

Family Name:	Congridae
Scientific Name:	Little: Gnathophis longicauda (Ramsay & Ogilby, 1888) (N.B. commonly but incorrectly cited as the N.Z. species G. habenatus / havenatus (Richardson, 1848) Largepore: G. macroporis Karmovskaya & Paxton, 2000 Umbrella: Gnathophis umbrellabius / umbrellabia (Whitley, 1946)
Recommended Status in S.A:	Data Deficient (all species)
Rationale:  The Gnathophis conger eels are included here because (i) there are few records of these species in South Australia; (ii) species in Congridae have life history characteristics that make them vulnerable to over-exploitation and population decline, such as relatively long-life span, delayed onset of maturity, and low frequency of production; (iii) very little is known about the habitat requirements, relative abundance over the geographic range and depth range, habits, and life history / population dynamics of these species; (iv) populations in some areas may be vulnerable to by-catch mortality in prawn and fish trawl on the continental shelf, but species-specific data are lacking, other than in the prawn trawl fishery in N.S.W., and in the Commonwealth-managed South East Trawl Fishery; and (v) generally, strongly site-associated benthic species may be vulnerable to site-specific habitat impacts (e.g. from trawling).

Page Contents

Current Conservation Status

No listings known

Distribution

Global

Little Conger Eel has been recorded from islands in the southern Indian Ocean; South Africa; Australia; New Zealand and the Chatham Islands (Castle, 1986, cited in Froese and Pauly, 2007; Paulin et al., 1989; Castle, in Gomon et al., 1994; Hutchins and Swainston, 2001).
Umbrella: Found in southern Australia, and around Norfolk I., New Zealand, Chatham Is., Kermadec Is. (Paxton et al., 1989; Paulin et al., 1989; Roberts, 1991; Francis, 1993).

Southern Australia

Little Conger Eel is found across southern Australia (southern N.S.W., Victoria, Bass Strait, Tasmania, S.A. and W.A.), mostly along the south-eastern and south-western coasts, rather than in the south (Paxton et al., 1989; Castle, in Gomon et al., 1994; Hutchins and Swainston, 2001; OZCAM database, 2007).
Largepore Conger Eel has been recorded from southern New South Wales, Victoria and south-eastern South Australia (Australian Museum records, Museum of Victoria records). The species is known mostly from Victoria (Karmovskaya and Paxton, 2000).
Umbrella: Mostly known from N.S.W., Victoria, northern Tasmania and South Australia (Australian Museum records, Museum of Victoria records; South Australian Museum records, cited in OZCAM database, 2007 and CSIRO, 2007). The species has also been reported from W.A. (West Australian Museum, 2003), with the record verified by E. Karmovskaya and J. Paxton (B. Hutchins, W.A. Museum, pers. comm., 2006).

South Australia

Little Conger Eel: For this report, only 7 records of Little Conger from in or near South Australian waters could be found: (i) one or two specimens from Venus Bay / Anxious Bay area, taken in prawn trawls in 1983 (S.A. Museum record F04755, listed as G. habenatus); (ii) 4 specimens from 1980, one taken at 50m deep SW of Port Lincoln; two unverified records from the Great Australian Bight (GAB) at 30m, and one unverified record from the eastern GAB at 18m (CSIRO Marine Research records L 591-01, T 1582-2, and L 590-01, all listed as G. habenata); (iii) a specimen from 124m, taken near the S.A. / W.A. border, south-west of Eucla (Museum of Victoria record A 22107, listed as G. longicaudatus) (OZCAM database, 2007).
Largepore Conger: Only one record could be found for this report, that being a specimen collected in 1962, from deep waters off the South-East of S.A. (i.e. west of Cape Jaffa and south of Kangaroo I. (Australian Museum record IB7136).
Umbrella Conger: Several records are known from the eastern Great Australian Bight trawl grounds (Anxious Bay area) (e.g. SAM record F04754; F07683 and F07687 - collected 1982-83; and another, F07684, from trawl block 62, south-eastern GAB). There is also a record from near the main jetty in Port Lincoln, Spencer Gulf (SAM record F 07742, collected 1995).

Habitat

Gnathophis conger eels occur mainly on the continental shelf, to more than 150m depth.
Little Conger Eel inhabits muddy / silty and sandy bottoms, particularly in deeper offshore waters (Castle, in Gomon et al., 1994; Hutchins and Swainston, 2001). It has been reported from continental shelf and upper slope waters (Paxton et al., 1989).
Largepore Conger: Recorded to about 164m deep (Karmovskaya and Paxton, 2000, cited by Eschmeyer, in Froese and Pauly, 2007).
Umbrella Conger Eel is reported from the depth range 12m – 165m, with most specimens to date recorded in the lower part of the depth range (140m +) (CSIRO et al., 2001).

Notes on the Biology

Size and Age

Little Conger Eel: G. longcaudis (cited as G. habenatus) grows to about 40cm or 43cm (Castle, 1986, cited by Froese and Pauly, 2007; Castle, in Gomon et al., 1994; Hutchins and Swainston, 2001). The maximum weight of a captured Little Conger Eel is 0.135kg, being a specimen taken from Norah Head in N.S.W. in 2001 (Australian Anglers Association, 2003).
Umbrella Conger: Grows to about 45cm (Paxton et al., 1989; Castle, in Gomon et al., 1994).

Diet and Feeding Behaviour

In general, Conger Eels feed on small fishes, crustaceans and cephalopods, primarily at night (Nelson, 1994; Australian Museum, 2003y). Congers in the genus Gnathophis eat primarily crustaceans, but also fish and invertebrates (Karmovskaya and Paxton, 2000). The Little Conger is reported to eat small crustaceans and polychaetes, which it hunts at night (Castle, in Gomon et al., 1994).

Reproduction

There is little available information on the reproduction, other than results of studies from New Zealand, which showed that a related species of Little Conger Eel (G. habenatus) spawns in autumn and winter. The pelagic larvae, which disperse widely along the coast, grow for approximately 10 months prior to metamorphosing to the juvenile stage, which occurs in summer (Castle and Robertson, 1974; Castle, in Gomon et al., 1994).
Although there appears to be no specific information on reproduction in these species, members of the sub-family Congrinae (to which Gnathophis congers belong) are known to reproduce only once in life, after a delayed period to maturity (Maigret and Ly, 1986, and Gothel, 1992).

Other Information

Little Conger Eel is reported to be part of the diet of Tiger Flathead (Coleman and Mobley, 1984; Kailola et al., 1993, cited by Morton et al., 2005).
In South Africa, Gnathophis species have been recorded in the diet of a Dasyatis stingray (Ebert and Crowley, 2003), but records of conger eels in the diet of similar stingrays in southern Australia could not be found for this report.

Fisheries Information

Southern Australia – Commercial

The Little Conger Eel is mostly taken by trawlers (Hutchins and Swainston, 2001).
In New South Wales, Little Conger Eel is commonly found in the bycatch of the shelf sector of the Ocean Prawn Trawl fishery. One survey recorded Little Conger Eel in 48% of the trawl shots in the shelf sector of this fishery, and the species was ranked 10^th of the top 50 bycatch species, in terms of frequency of occurrence (N.S.W. Department of Primary Industries, 2004). Umbrella Conger is also a bycatch species in the shelf sector of the Ocean Prawn Trawl Fishery (occurrence in 8% of the trawl shots). In the deepwater sector of the Ocean Prawn Trawl Fishery, Largepore Conger is a minor part of the bycatch (e.g. 1% occurrence) across all trawls (N.S.W. Department of Primary Industries, 2004).
In the otter trawl sub-fishery of the South East Trawl Fishery, an Integrated Scientific Monitoring Program (ISMP) reported that in 109 trawl shots, about 136kg of eels in the Congridae were retained and 298kg were discarded (Wayte et al., 2004).
In South Australia, Littler Conger Eel has been recorded from the prawn trawling bycatch in the eastern Great Australian Bight (i.e. Anxious Bay area) (South Australian Museum data, cited in OZCAM database, 2007).
There are commercial fishing records from Port Phillip Bay and Bass Strait of Little Conger Eel being taken in the bycatch (Anonymous, 2002b).

Southern Australia – Recreational

Little Conger Eel is infrequently taken by anglers (Hutchins and Swainston, 2001). Some fishing clubs and associations keep records of the maximum sizes caught (e.g. 0.135kg, being a specimen taken from Norah Head in N.S.W. in 2001 – Australian Anglers Association, 2003).
For Gnathophis conger eels, there are no species-specific records from recreational fishing available for this report. It is noted that the National Recreational and Indigenous Fishing Survey (Henry and Lyle, 2003) recorded small numbers of conger eels of unspecified species being taken during the survey time period (2000-2001) (see synopsis on Conger verreauxi and C. wilsoni).

Vulnerable Characteristics of the Species

Species in Congridae have life history characteristics that make them vulnerable to over-exploitation and population decline, such as relatively long-life span, delayed onset of maturity, and low frequency of production (see synopses for Conger wilsoni and Conger verreauxi).
Generally, benthic species with strong site association may be vulnerable to site-specific habitat impacts (e.g. trawling).

Threatening Processes

Processes that damage the coastal benthic environment (e.g. trawling, dredging, channel construction) may pose a threat to populations in some areas, given the distribution and benthic habit, but there is no specific information available.
In eastern Australia, a study of the susceptibility of trawl-caught fishes to population impacts (Stobutski et al., 2001) ranked fish bycatch species according to two overriding characteristics (based upon biological and ecological criteria): (i) the susceptibility to capture and mortality due to prawn trawling, and (ii) the population's capacity to recover after depletion. The rank of each species on these two characteristics determined its relative capacity to sustain trawling, and therefore its priority for research and management. Species that were the least likely to be sustainable included those in the Congridae. These species are highly susceptible to capture by trawls, they are benthic or demersal, their primary habitat is soft sediments, and their diet may include animals targeted in commercial fisheries. The recovery capacity of these species is also low, with the estimated removal rate by trawling (Stobutski et al., 2001). It is noted that Little Conger Gnathophis longicauda is a significant bycatch species in the New South Wales Ocean Prawn Trawl fishery.

Research and Management Requirements

When recorded in trawl bycatch in S.A., Gnathophis specimens (and collecting details) should be sent to the South Australian Museum.
A risk assessment should be undertaken in all trawl fisheries in which Gnathophis are significant bycatch (e.g. New South Wales Ocean Prawn Trawl fishery), and methods to reduce bycatch of congrid eels should be implemented where possible. Current methods, such as adoption of new gear designs, that are being trialled in N.S.W. and S.A., are discussed in other chapters of this report (e.g. see Callyionymidae)
In S.A., a system should be developed for the ongoing collection and monitoring of bycatch data from the West Coast Prawn Fishery (as currently occurs in the Spencer Gulf Prawn Trawl Fishery), sufficient to “enable identification of long-term trends in bycatch” (Australian Government DEH, 2004b).

Other Information

Karmovskaya and Paxton (2000) revised the species in Gnathophis, and considered that the Gnathophis habenatus / havenatus (Richardson, 1848), species name that is commonly given to the Little Conger Eel in southern Australia (e.g. Hutchins and Swainston, 1986, 2001; Castle, in Gomon et al., 1994), refers to a related species from New Zealand, and that the Little Conger Eel in southern Australia is G. longicauda.