|Scientific Name:||Phyllopteryx taeniolatus|
|Species Authority:||(Lacépède, 1804)|
|Taxonomic Notes:||Synonym = Phyllopteryx lucasi Whitley, 1931.|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Reviewer/s:||Morgan, S.K. & Martin-Smith, K. (Syngnathid Red List Authority)|
More information is available about weedy seadragons than when the species was last assessed, and this has resulted in a reassessment of Near Threatened (NT).
There is no evidence of changes in population sizes, but its habitat has been adversely affected by pollution. The extent of degradation and loss of habitat has not been measured but, at this stage, probably represents a small proportion of the total extent of habitat available.
Some issues point towards criteria within the Endangered (EN) category, and these points are described below. None of the information provides compelling evidence for trends in occurrence or occupancy.
The extent of occurrence is estimated to be 2,000 km², which is below the 5,000 km² threshold for EN B1 and well below the 20,000 km² threshold for Vulnerable (VU). Total area of occupancy may be less than 2,000 km² (VU B2 threshold) but at this time is unknown. Criterion B2 therefore cannot be used.
Seadragons have been sighted at numerous locations within the range but it is impossible to determine how fragmented occurrence is. Therefore, sub-criterion B1a cannot be used at present.
EN B1b(iii) (continuing decline in area, extent and/or quality of habitat) is met. Seadragon habitats such as algal covered reefs are being adversely affected by human activities and loss in quality and quantity of habitat has been documented (Baker 2003). The threat to habitat is greatest near major urban centres (e.g., Sydney, Perth, Adelaide, Melbourne), where discharge of storm water and treated sewage leads to eutrophication and increased sedimentation. The threat to seadragons is lessened to an extent by the occurrence of seadragons at sites distant from these cities, provided that these areas are biologically connected through movement or dispersal.
In Tasmania, the macroalgae-covered reefs on which seadragons occur face another threat. Over the last 20 years, the sea urchin Centrostephanus rogersii, has become more common and increased its range around the state. The increase in sea urchins is considered to have resulted from harvesting of rock lobster, a known predator of urchins, and climate change. Grazing by urchins reduces the abundance of kelp and other macroalgae through the formation of urchin barrens. Furthermore, significant losses of giant kelp (Macrocystis pyrifera) have been documented over the past 20 years (Edyvane 2003), associated with increased water temperatures. The reduction in macroalgae could adversely affect seadragons although this has not been demonstrated.
In South Australia, a possible contraction in extent of occupancy has been mentioned (Baker 2003). Historical records exist from benthic surveys in Gulf St Vincent in the period 1965–1971, where reportedly “numerous weedies were observed” in northern Gulf St Vincent, adjacent to the city of Adelaide (S. Shepherd, pers. comm. to Baker, 2003). No sightings in this area have been reported to Dragon Search during the late 1990s and early 2000s. Admittedly the lack of recent sightings might be due to the lack of popular diving spots in the northern gulf, and the lack of systematic surveys in recent years (Baker 2003). However, the occurrence of seadragons might have been affected by significant habitat degradation and loss recorded since the 1960s in this part of the gulf. In particular, large areas of seagrass have been lost in waters deeper than 10 m south of a line between Ardrossan and Port Prime (Baker 2003). More rigorous monitoring of seadragon populations would assist in assessing changes in occupancy such as this.
In summary, the lack of trend data means that seadragons cannot be described as meeting any of the threatened categories at present, but it nearly meets Endangered under criterion B (currently only one sub-criterion (B1b(iii)) is met). Therefore it is assessed as NT. The greatest threat is habitat loss but at this stage the loss is limited to regions immediately around large cities, which in Australia are well separated.
Continued monitoring is required to establish population trends. Research is also needed to establish areas of occupancy.
|Range Description:||Weedy Seadragons are found along much of the southern Australian coastline, from near Newcastle, NSW (approx 32° 56’S) southwards to Actaeon Island, TAS (43°32’S) and westwards through VIC and SA to Geraldton, WA (28°46’S) (Pogonoski et al. 2002).
Phyllopteryx taeniolatus can be locally common in NSW, VIC and TAS. In Victoria it can often be seen in shallow areas of Port Phillip Bay (surrounded by the city of Melbourne) and Western Port. In NSW it is often found on sheltered reefs in waters exceeding 15 m, but is also found in shallower waters in large open bays (Kuiter 2000a). In TAS large numbers have been observed at a number of sites in the D’Entrecasteaux Channel, particular in the Blackman’s Bay/Kingston area (Martin-Smith and Davey, unpublished data).
Follow the link below for map of the known range of P. taeniolatus.
Native:Australia (New South Wales, South Australia, Tasmania, Victoria, Western Australia)
|FAO Marine Fishing Areas:||
Indian Ocean – eastern; Pacific – southwest
|Range Map:||Click here to open the map viewer and explore range.|
No firm population estimates exist for Weedy Seadragons, but an approximate estimate can be made using certain assumptions. Estimates of densities can be obtained for several locations, although at this stage no analyses of trends in densities are available.
From the study by Sanchez-Camara and Booth (2004) near Sydney, NSW, using certain assumptions about the width of transects (recorded as 350 long, and assumed to be approximately 20 m wide), densities averaged 58 fish ha-1 at the 2 sites where most work was done. At a nearby site with fewer fish where less work was done, densities were about a quarter of these estimates. Densities at two sites in the Derwent estuary in TAS have been estimated using mark-recapture methods at 12–20 and 4–10 fish ha-1 (M. Davey and K. Martin-Smith, unpubl. data).
In making an overall population estimate, the following estimations and assumptions were made:
1. The sites at which Sanchez-Camara and Booth (2004) worked were chosen because relatively frequent sightings had been made there previously. An average density across the distribution would be lower, probably lower even than the third site used by Sanchez-Camara and Booth (2004) and the sites in TAS surveyed by Davey and Martin-Smith. A figure of 5 fish ha-1 was used (approximately 10% of upper estimate by Sanchez-Camara and Booth (2004)).
2. The coastline along which Weedy Seadragons occur is an estimated 20,000 km long (including TAS).
3. The species occurs most frequently in a thin strip of shallow water along the coastline, most frequently along the edge of reefs supporting stands of macroalgae. This strip is estimated to be, on average, 100 m wide, giving a total of 200,000 ha of occupancy.
At five fish per ha, the estimated total number of Weedy Seadragons is ~ 1,000,000. Confidence limits cannot be stated but the estimate is clearly based on very loose assumptions. The purpose of making such an estimate is to give perspective to the number of fish that might be removed from the wild (see Threats, below).
Mapping of habitat at sites far from major population centres and research into variability in habitat use at different sites is required to make the estimate of total population size more rigorous.
|Habitat and Ecology:||
Weedy Seadragons occur over rocky reefs supporting stands of kelp or other macroalgae, or over adjacent stretches of bare sand (Kuiter 2000a). Phyllopteryx taenoliatus is most commonly observed along reefs in areas abutting sand where it feeds on mysids and small crustaceans (Kuiter 2000b). Individuals have been shown to have broad, overlapping home ranges that can vary in length from 50–150 m, and be up to 50 m wide (Sanchez-Camara and Booth 2004). Baker (2000a) found that Weedy Seadragons also live in association with sponges. The species’ depth distribution ranges from shallow bays down to reefs at depths of up to 50 m.
The extent to which the species occurs over seagrass meadows is unknown and needs investigation. The other large syngnathid from southern Australian waters, the Leafy Seadragon, was not considered to be associated with seagrass until recently. For that species, ultrasonic tracking of individuals demonstrated that they were at least as likely to occur over seagrass as over algae. Although this may not be true for Weedy Seadragons, it is important to establish any use of seagrass meadows because seagrasses are known to be adversely affected by pollution in southern Australia; habitat use is therefore important in the consideration of potential threats (see Threats, below).
The breeding season for Weedy Seadragons is early summer and there is one brood per season. Males carry the eggs externally below their tail and the skin forms a cup on each egg during deposition. Incubation time is about eight weeks and up to about 250 young hatch. Some individuals mature in one year, but most usually breed in their second year when fully grown (Kuiter 1993). Baker (2000a) reports that brooding males have been observed in NSW from mid-winter to mid-summer, but never from February to June, despite sightings of over 350 seadragons during this period.
In the Sydney area and in southern NSW, aggregations of between 20 and 40 seadragons have been observed, respectively (Baker 2000a).
Phyllopteryx taeniolatus feeds on mysids and other small crustaceans and attains about 45 cm in total length (Kuiter 1993).
The main threats to the weedy seadragon include; 1) intrinsic life history traits thought to limit dispersal, 2) habitat degradation, 3) collection for trade:
1. Weedy Seadragons lack a caudal fin and are weak swimmers; in conjunction with a lack of a dispersive egg phase, this potentially makes them vulnerable to habitat loss and degradation, which is the main threat to this species.
2a. Both algae-covered reefs and seagrass meadows have been adversely affected by human activities and loss in quality and quantity of habitat has been documented (Baker 2003). The degradation of habitat is worst near major urban centres (e.g., Sydney, Adelaide, Melbourne, Perth), where discharge of storm water and treated sewage leads to eutrophication and increased sedimentation. Losses of seagrass have been particularly severe along the metropolitan coasts and are well documented (Short and Wyllie-Echeverria 1996). Reefs have been more strongly affected by increased rates of sedimentation resulting from human activities such as sand dredging, land reclamation and coastal urban development (Baker 2003).
2b. Urchin consumption of kelp beds and loss of giant kelp in TAS through climate change.
3. The legal and/or illegal collection of wild specimens has little likelihood of causing long-term changes in population sizes, unless demand increases substantially. The small numbers taken could result in the reduction or loss of groups of animals at particular sites, but this is unlikely to result in measurable effects on populations. Weedy Seadragons have not been reported in surveys of incidental bycatch in trawl fisheries of southeastern Australia.
Legislation (Source: Pogonoski et al. 2002)
1. Protected Species in NSW under Fisheries Management Act 1994.
2. The Tasmanian Living Marine Resources Management Act 1995 prohibits the take of all syngnathids in Tasmania (by non-permit holders).
3. Protected Aquatic Biota in Victoria.
4. Subject to Export controls since 1st January 1998, in the Commonwealth Wildlife Protection (Regulation of Exports and Imports) Act 1982.
5. Listed as marine species under s248 of The Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).
6. No Australian Society for Fish Biology listing.
More information (Source: Martin-Smith et al. 2003)
All Australian pipehorses have been protected in Australian Commonwealth (federal) waters (greater than three nautical miles from the coast) since the beginning of 1998. As most pipehorses are caught in Commonwealth waters they are protected under the Environment Protection and Biodiversity Conservation Act 1999 wherein they are ‘listed marine species’. It is an offence to take, trade, injure or kill listed marine species except under permits issued by the Minister of the Environment. Such permits for exports of syngnathids are issued subject to a management plan, which must be approved by the executive agency, Environment Australia (within the Department of Environment and Heritage). Legal protection is variable for pipehorses caught in Australian State waters (less than three nautical miles from the coast), ranging from full to no protection.
|Citation:||Connolly, R. 2006. Phyllopteryx taeniolatus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 25 May 2013.|
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