© 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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Ladder Eel

Family Name:	Congridae
Scientific Name:	Scalanago lateralis Whitley, 1935
Recommended Status in S.A:	Data Deficient
Rationale:  The Ladder Eel is included here because (i) there are few records of Scalanago lateralis across its range, from few localities, and the species appears to have a limited geographic distribution 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, full depth range, relative abundance, habits, and life history / population dynamics of this 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; 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

Southern Australia

The Ladder Eel is known from few localities in south-eastern Australia (i.e. Sydney to Jervis Bay), and also from a small number of records from the Great Australian Bight (Castle, in Gomon et al., 1994; Paxton et al., 1989, cited in Froese and Pauly, 2007; CSIRO Marine Research records, cited in CSIRO, 2007), and southern W.A., between the Houtman Abrolhos / Geraldton area and Albany (Australian Museum records, unverified).
The type specimen was taken from off Bondi Beach near Sydney, in the 1930s (Whitley, 1935, cited by Eschmeyer, 2003).

South Australia

There are few records from South Australia. Only 3 museum records could be found: (i) one from the Port Lincoln area, collected in 1961; (ii) a specimen from deeper waters seaward of Venus Bay, collected in a prawn trawl in 1983 (South Australian Museum records, cited in OZCAM database, 2007); and (iii) one specimen collected in 1990, in the eastern Great Australian Bight, at approximately 142m deep (Museum of Victoria record A9044, cited in OZCAM database, 2007).

Habitat

The Ladder Eel occurs in continental shelf waters (Paxton et al., 1989).
The full depth range has not been recorded. Castle (in Gomon et al., 1994) reported the species from inshore, turbid waters, but there are also records from deeper waters of the continental shelf (e.g. ~ 142m deep: Museum of Victoria record A9044, cited in OZCAM database, 2007; 36m, 85m, 120m deep: CSIRO Marine Research records, unverified, cited in CSIRO, 2007).

Notes on the Biology

S. lateralis grows to about 35cm long (Castle, in Gomon et al., 1994).
Members of the Congridae feed on small fishes and crustaceans, primarily at night (Nelson, 1994, cited in Froese and Pauly, 2007).

Fisheries Information

The Ladder Eel apparently occurs in deeper waters in the Great Australian Bight (that are trawled), and possibly other trawl grounds in south-eastern and south-western Australia. However, it is noted that the species is not listed in a number of Commonwealth trawl bycatch reports, from south-eastern Australia, and the Great Australian Bight. No information is available for this report on the bycatch of Ladder Eel, and the species is not targeted by fisheries.

Vulnerable Characteristics of the Species

The species appears to have a limited geographic distribution in South Australia.
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.
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, and channel construction) may pose a threat to populations in some areas, given the distribution and benthic habit, but there is no specific information available.
Given the distribution and depth range of this species, it is likely to be part of the bycatch in trawls (both State and Commonwealth waters). For example, the species has been recorded in the prawn trawling grounds of the eastern Great Australian Bight (South Australian Museum records). It is noted that, although there is also a trawl-caught specimen (Museum of Victoria) from deeper continental shelf waters in the Great Australian Bight (A 9044), the species has not been reported in to date in fish trawl bycatch monitoring programs from the GAB (e.g. Brown and Knuckey, 2002; Daley et al., 2006). Mortality of Ladder Eels in the bycatch in trawl fisheries might pose a threat to populations of this species in some areas, but there is no specific information.

Research and Management Requirements

The Ladder Eel is a little known species, with isolated records from few areas across southern Australia. Apart from lack of information about the full distribution and depth range, virtually nothing is known of the habitat requirements, relative abundance, biology or population dynamics of this species, and research would be required to fill these knowledge gaps.
When recorded in trawl bycatch in S.A., specimens (and collecting details) should be sent to the South Australian Museum. Any ladder eel specimens in the unregistered fish collection at the South Australian Museum should be identified to species level.
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).