|Scientific Name:||Hydrolagus ogilbyi|
|Species Authority:||(Waite, 1898)|
|Taxonomic Notes:||Synonym = Hydrolagus (Psychichthys) waitei Fowler, 1908.
This species looks very similar to Hydrolagus lemurs and partly overlaps in range although H. ogilbyi is reported to occur in shallower waters and may grow to larger sizes (Last and Stevens, 1994). However, data from the study of large collections of H. lemurs and H. ogilbyi indicate a much larger overlap in range, both geographic and bathymetric, and size than indicated by Last and Stevens (1994). If H. ogilbyi is indeed restricted in range as indicated by Last and Stevens, then the large number of records of H. ogilbyi from the Great Australian Bight and Western Australia may be misidentifications. Color is a primary feature for identification, however it appears to be quite variable within both species and these two species are easily mistaken. Due to the confusion with regard to identification of H. ogilbyi and H. lemurs a closer examination these two species is recommended to determine species distinctions.
Reference to H. ogilbyi from Japan (Tanaka, 1908) is probably erroneous and likely a misidentification of Chimaera phantasma.
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor(s):||Dagit, D.D. & Kyne, P.M.|
|Reviewer(s):||Graham, K.J., Fowler, S.L. & Compagno, L.J.V. (Shark Red List Authority)|
Hydrolagus ogilbyi is endemic to Australia with a range apparently restricted to southeastern Australia including New South Wales, Tasmania and South Australia, although collection records indicate a possible wider range including southern Queensland, the Great Australian Bight and perhaps parts of Western Australia. Typically found on the continental shelf and upper slope at depths of 40 to 524 m. The species is reported as apparently relatively common to abundant in parts of its range, but in the first instance confirmation of taxonomic distinction between H. lemurs and H. ogilbyi is needed to better define distribution. Fishery-independent surveys on the NSW upper slope have documented significant declines (of 96.4% overall and >99% in some regions) in the catch rate of "silver ghostsharks" (documented as mostly H. ogilbyi, these surveys were likely to have taken some H. lemurs, however the bulk of catches appeared to be H. ogilbyi) over a 20 year period as a result of intensive trawl fishing on the narrow NSW continental slope. This area may represent a significant proportion of the range of this species, although as stated above range needs better definition. There are, however, parts of the species' range, which receive little fishing pressure and serve as refuges for this species. As such, the species is assessed as Near Threatened, given documented declines in some areas which highlight the vulnerability of Hydrolagus species to trawling, continued heavy fishing in parts of its range, but a wide geographical and bathymetrical distribution and the existence of some refuge areas.
|Range Description:||Last and Stevens (1994) reported H. ogilbyi as apparently restricted to New South Wales, Tasmania and eastern South Australia, but it appears to be more widespread based on surveys and data from voucher specimens in museum collections. To the west these indicate a much wider range extending into the Great Australian Bight and parts of Western Australia. Along the east coast it has been recorded north of Coffs Harbour to the Queensland border (K. Graham pers. comm.).|
Native:Australia (New South Wales, Queensland, South Australia, Tasmania, Victoria)
|FAO Marine Fishing Areas:||
Indian Ocean – eastern; Pacific – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||A single endemic population restricted to southeastern Australia. Reported to be fairly common and relatively abundant, particularly off Tasmania.|
|Habitat and Ecology:||
Continental shelf and upper slope dweller occurring in depths of 40 to 524 m on or near the bottom. May share similar ecology and life history characteristics of other shelf and upper slope dwellers such as H. lemurs and H. colliei.
Life history parameters
Age at maturity (years): Unknown.
Size at maturity (body length): ~40 cm BDL (male & female).
Longevity (years): Unknown.
Maximum size (total/body length): ~102 cm TL (with filament); 85 cm (without filament); ~55 cm BDL.
Size at birth (cm): Unknown.
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: Unknown.
Annual rate of population increase: Unknown.
Natural mortality: Unknown.
A large proportion of the known range of H. ogilbyi has been subject to considerable trawling pressure. Within the Southern and Eastern Scalefish and Shark Fishery (SESSF), Hydrolagus ogilbyi is considered to have a high catch susceptibility to otter trawl, a medium catch susceptibility to auto hook gear and a low susceptibility to shark gillnet, shark hook and trap/pot gear (Walker 2004) (catch susceptibility is defined as "availability" x "encounterability" x "selectivity"' x "post-capture mortality"; Walker 2004). If the species is found to occur into the Great Australian Bight it is likely taken as bycatch in the Great Australian Bight Trawl Sector (GABTS) of the SESSF. The GABTS operates over a large geographical area and is managed by limited entry with 10 fishing concessions and while overall effort is low, there is a trend of increasing effort (Lynch and Garvey 2003). Holocephalans are not reported in the top 40 species/species groups recorded in the fishery (Lynch and Garvey 2003), but are likely to form negligible bycatch.
Significant declines in the catch of "silver ghostsharks" from 1976-77 to 1996-97 from the upper slope trawl fishery off NSW have been documented by fishery-independent surveys (Graham et al. 2001). Graham et al. (2001) stated that "silver ghostsharks" were identified as H. ogilbyi. Sampling for this study occurred in 200-605 m and so it is likely both H. ogilbyi (which occurs at 40-524 m) and H. lemurs (which occurs at 190-825 m) were captured, however the bulk of catches did appear to be H. ogilbyi (K. Graham pers. comm.). The aggregated data does not allow species-specific declines to be elucidated, however, overall "silver ghostshark" declined from a mean catch rate of 8.3 kg/hour to 0.3 kg/hour in the twenty year period, equating to a decline of 96.4%. Reductions are even more striking when data are broken down into region, with the mean catch rate off Eden-Gabo Island (northern NSW/southern Victoria) declining from 17.4 kg/hour in 1976-77 to <0.1 kg/hour in 1996-97, equating to a decline of greater than 99.4%. If, as it appears, the majority of the catch was H. ogilbyi, this represents significant local declines of the species and indicates the vulnerability of Hydrolagus species off eastern and southeastern Australia to population reduction. The relatively narrow continental slope off central/southern NSW, including most of the depth range of H. ogilbyi, is intensively fished and there would be continued pressure on Hydrolagus species in this area.
There are regions of the species' range, however, that receive little fishing pressure. If the species extends into southern Queensland, fishing is not as intense on the slope there and off northern NSW. Indeed, there is little outer shelf/upper slope trawling north of Port Stephens, NSW (K. Graham pers. comm.). Furthermore, there are significant areas of the outer shelf off western Victoria, which may serve as a refuge from trawling due to rough bottoms. Some areas off Tasmania also receive little fishing pressure.
A continued effort should be made to gain bycatch information in fisheries within the range of this species.
None are known. Detailed comparative study of H. ogilbyi and H. lemurs is recommended to verify the distinction between these two species. Additional study of life history characteristics as well as geographic and depth range parameters is also recommended. Additional data on bycatch levels and landings is needed.
The effective implementation of the Australian National Plan of Action for the Conservation and Management of Sharks (Shark Advisory Group and Lack 2004) (under the FAO International Plan of Action for the Conservation and Management of Sharks: IPOA?Sharks) will help to facilitate the conservation and sustainable management of all chondrichthyan species in Australia.
|Citation:||Dagit, D.D. & Kyne, P.M. 2006. Hydrolagus ogilbyi. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 26 October 2014.|
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