|Scientific Name:||Phycodurus eques|
|Species Authority:||(Günther, 1865)|
|Taxonomic Notes:||Synonym = Phycodurus glauerti Whitley, 1939.|
|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 leafy seadragons than when the species was last assessed, and this has resulted in a reassessment of Near Threatened (NT). There remains a paucity of information describing population fluctuations, population size and life history traits, therefore the assessment focuses on criterion B (geographic range).
Population sizes have probably been reduced marginally through incidental impacts of fishing and the species’ habitat certainly has been adversely affected by pollution. However, these reductions have not been measured and probably represent a small proportion of totals of fish abundances and habitat extent.
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, however this is largely due to the absence of data, rather than information that points towards population stability.
The extent of occurrence is estimated to be 1,400 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 is possibly less than the VU threshold of 2,000 km² (given the approximate extent of occurrence calculated above), but at this time is unknown. Criterion B2 therefore cannot be used.
EN B1b(iii) (continuing decline in area, extent and/or quality of habitat) is met. Seadragon habitat such as algal covered reefs and seagrass meadows are being adversely affected by human activities and loss in quality and quantity of habitat has been documented (Baker 2003). The loss of habitat is most severe near major urban centres (e.g., Perth, Adelaide, Melbourne), 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). The threat to seadragons may be lessened to an extent by the occurrence of seadragons at sites distant from these population centres, provided that these areas are biologically connected through movement or dispersal.
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.
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 on sub-criterion (B1b(iii)) is met). Therefore it is assessed as NT.
Continued monitoring is required to establish population trends. Research is also needed to establish areas of occupancy.
|Range Description:||Leafy seadragons appear to be most abundant in SA and southern WA. Until recently, the range was considered to form a continuous stretch of coastline from near Perth on the southern west coast of WA to Wilson’s Promontory in Vic (Kuiter 2000b). Recent sightings of live animals by divers have extended the known range along the WA coastline as far north as the Abrolhos Islands, west of Geraldton (Baker 2002). Unconfirmed reports of sightings come from Bass Strait Islands (King Is., Kent Group) of NW TAS (K. Martin-Smith, pers. comm).
The extent of occurrence can be approximated as the length of coastline along which it occurs (~ 14,000 km) and the width of the strip of habitat suitable for it to occupy along this coastline (less than 1 km in most places, and for this calculation assumed to be 0.1 km wide). The extent of occurrence is therefore estimated to be 1,400 km². Seadragons have been sighted at numerous locations within the range but it is impossible to determine how fragmented occurrence is. Total area of occupancy is possibly less than 2,000 km² (given the approximate extent of occurrence calculated above), but at this time is unknown.
The depth range of Leafy Seadragons is not well documented. Most reported encounters are with divers, and therefore necessarily in waters less than about 20 m. Seadragons have, however, been recorded down to 30 m in SA, WA and VIC (Kuiter 2000b).
Native:Australia (South Australia, Victoria, Western Australia)
|FAO Marine Fishing Areas:||
Indian Ocean – eastern
|Range Map:||Click here to open the map viewer and explore range.|
No firm population estimates exist for Leafy Seadragons, but an approximate estimate can be made using certain assumptions. Just one estimate of density exists for this species, from a single location at one time. Connolly et al. (2002a) estimated the density of Leafy Seadragons around West Island, in Encounter Bay, SA, using a mark/re-sighting method and a capture/recapture algorithm. The density of larger juveniles and adults at this site was 57 fish per ha. Small juveniles (< 100 mm) were not included in the study. In making a population estimate, the following estimations and assumptions were made:
1. The site at which Connolly et al. (2002a) worked was chosen because relatively frequent sightings had been made there previously. An average density across the distribution would be lower, probably much lower, and a figure of 5 fish per ha was used (approximately 10% of estimate by Connolly et al. (2002a)).
2. The coastline along which Leafy Seadragons occur is an estimated 14,000 km long.
3. The species occurs most frequently in a thin strip of shallow water along the coastline, typically in stands of macroalgae or in seagrass meadows. This strip is estimated to be, on average, 100 m wide, giving a total of 140,000 ha of occupancy.
At 5 fish per ha, the estimated total number of Leafy Seadragons is ~700,000. 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:||
Leafy Seadragons were until recently considered to occur predominantly near rocky reefs supporting stands of kelp or other macroalgae, where they have been observed feeding on mysids and other crustaceans (Kuiter 2000a). Recent telemetry using ultrasonic transmitters has shown, however, that this species is just as prevalent over shallow (5–15 m depth) Posidonia seagrass meadows and patches of sand amongst seagrass (Connolly et al. 2002b).
Leafy Seadragons tracked over periods of up to 10 days typically remained within well-defined home ranges of up to 5 ha (Connolly et al. 2002b). Patterns of movement are characterised by short bursts (at average velocities of 2–17 m/h) punctuating long periods (up to 68 h) without movement. No diel pattern of movement is apparent (Connolly et al. 2002b).
As with other syngnathids, male seadragons carry the fertilized eggs. For Leafy Seadragons, the male carries about 200 eggs on the exposed surface of the underside of its tail (there is no pouch).
This species can survive for at least two to three years in aquaria if supplied with its specific live food requirements (P. Quong, pers. comm. in Pogonoski et al. 2002). Longevity in situ is not known. Phycodurus eques attains a maximum length of about 35 cm (Kuiter 1993).Mating reportedly occurs during summer months (Kuiter 2000b). Genetic structure of populations has not been measured, nor has any aspect of reproduction been quantified (e.g., number of mates, number of broods per season).
Phycodurus eques is particularly well camouflaged, with a number of frond-like appendages that resemble kelp. The species also rocks back and forth with wave action, increasing its resemblance to coastal algae swept by coastal surge (Gomon et al. 1994).
Leafy 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 as well as to incidental harvesting during commercial fishing (Connolly et al. 2002b). These are the two main threats.
Leafy Seadragons are associated with seagrass beds and reefs supporting macroalgae (Connolly et al. 2002b). These habitats have been adversely affected by human activities and loss in quality and quantity of habitat has been documented (Baker 2003). The loss of habitat is most severe near major urban centres (e.g., Perth, Adelaide, Melbourne), 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).
Connolly et al. (2002b) report anecdotal evidence that Leafy Seadragons are killed as incidental bycatch in the trawling industry in SA. Fishers have indicated that on occasions they catch “large numbers” of Leafy Seadragons. This information remains at the level of anecdote however, and neither the rate nor distribution of incidental catch have been substantiated. Measurement of incidental catch in SA would be beneficial, in that bycatch rates, compared with in situ densities, could be used to establish the relative threat posed by fisheries.
The legal collection of wild specimens has little likelihood of causing long-term changes in population sizes. The small numbers taken under legally issued permits could result in the reduction or loss of groups of animals at particular sites, but this is unlikely to result in measurable effects on regional populations. If demand increases substantially, illegal collection could threaten local and perhaps regional populations, although this possibility should remain unlikely given the difficulties associated with illegal international export.
This species is a major attraction for the dive industry in southern Australia, and it has been made the official fish emblem in the state of South Australia. Recreational divers often harass or disturb individuals (Kuiter 2000a). Suitable protocols for divers should be encouraged to protect local populations, but the disturbance probably does not harm the long-term prospects for regional populations.
Legislation (Source: Pogonoski et al. 2002)
1. Totally protected species in South Australian Waters (since 1987).
2. Protected Aquatic Biota in Victoria.
3. Totally Protected Fish Status in Western Australian Waters (since 1991).
4. Subject to Export controls since January 1st 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)
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.
All states of Australia are currently implementing systematic series of Marine Protected Areas (MPAs). Different states are at different stages of this process. The most important development for Leafy Seadragons is that a new MPA is close to being declared (it was released as a draft plan earlier in 2005) in southern Gulf St Vincent in the state of SA. The proposed MPA will include areas (e.g., Encounter Bay and northeastern Kangaroo Island) in which a large proportion of public sightings of seadragons occur. The protection of these areas could substantially decrease the perceived vulnerability of the species to human activities, in particular to commercial fishing. At this stage, however, levels of protection and locations of zones of high protection within the proposed MPA have not been finalised. Furthermore, MPAs offer no immediate protection against eutrophication and sedimentation threats to habitat from land-based sources.
|Citation:||Connolly, R. 2006. Phycodurus eques. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 10 March 2014.|
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