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Leafy seadragons are exquisitely camouflaged fish. Belonging to the same family as seahorses and pipefish (Syngnathidae), they resemble these with their elongated snout and bony-plated body. Leafy seadragons are yellowish-brown to green in colour, although they may vary depending on their age, diet or location. The pectoral fins are located on the neck, and a dorsal fin runs along the seadragon's back. As their common name suggests, there are a number of leaf-like appendages along the body, which help to make these fish resemble the seaweed of their habitat. The eyes are located above the elongated snout and there are a number of defensive spines along the sides of the body.
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).
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).
Populations of P. eques have been declining due to both habitat destruction and aquarium harvest. Many conservation efforts including diver education, research efforts, and habitat preservation are currently underway in Australia to protect this species from decline (Dragon Search 2000).
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.
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