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Potbelly Seahorse Hippocampus bleekeri Fowler, 1908
[CAAB 37 282010]

Distribution Map see an interactive map here (new window)

The Potbelly Seahorse is the largest and probably the most common seahorse in southern waters and is locally abundant in some areas. Until recently, this species was called Hippocampus abdominalis, which may be restricted to New South Wales waters. Further work is needed to confirm the presence of two distinct species.

Distribution, ecology and habitat:

Endemic to temperate waters of Southeastern Australia, from the northern Great Australian Bight, South Australia, to off Lakes Entrance, Victoria and south to the Derwent Estuary, Tasmania; benthic in shallow estuaries and coastal rocky reefs to at least 35 m. In southern Tasmania, the species inhabits muddy bottoms or areas near reef edges near the entrance to large estuaries. The Potbelly Seahorse uses its prehensile tail to cling to kelp holdfasts (Ecklonia radiata), sponges and man-made objects that provide anchorage in currents.

Size:

The largest known seahorse, reaching 350 mm TL, 230 mm in height.

Food and feeding:

Feed by sucking up small prey from rocks or weed, also feed on passing zooplankton; diet consists largely of small crustaceans, in particular amphipods, caridean shrimp and peracarids.

Reproduction and early life history:

Reproduction: Sexes separate, reproduction a form of viviparity or ovoviviparity, whereby the males give birth to tiny independent young. The female uses an ovipositor to transfer her eggs into an elaborate enclosed pouch under the abdomen of the male. The male not only fertilizes the eggs inside the pouch and provides physical protection for the developing embryos, he also osmoregulates and aerates the embryos and may provide some nourishment until the offfspring are born. H. bleekeri breed year round, with a peak during the warmer months.
As with other seahorses, this species exhibits elaborate courtship behaviour. Females may attract a number of competing males which pump their pouches by brightening their pouches and inflating and emptying them to entice her to deposit her eggs. Although males and females do not form monogamous pairs and promiscuous courtship behaviour has been observed, genetic studies of male broods in several Tasmanian populations showed that all males studied had mated monogamously. Males, however, may switch mates between broods.
During summer, males incubate up to 4 broods. One male seahorse in the aquaculture industry reportedly produced a brood of 1116 young.
Eggs: A gravid female can produce more than 400 eggs per brood.
Larvae: Pelagic young are born at 15-21 mm in height after a gestation of about a month. They are morphologically similar to the adults, but have angular spines of moderate length along the trunk and anterior tail ridges; the spines diminish in size in post-pelagic young. Pelagic larvae cling to each other or floating algae and seagrass leaves. Young have been described (as H. abdominalis).

Characteristics:

Meristics: D 27-30; A 4; P 14-16; trunk rings 12-13 (usually 13); tail rings 44-48; subdorsal rings 4-5 + 1-2.
Head and body: Head small to moderate, snout usually short; trunk quite distended ventrally in adult females; snout moderately long, shallow; region between head and trunk strongly constricted.
Spines and tubercles: Pelagic young with angular spines of moderate length along trunk and anterior tail ridges. Spines diminishing in relative size in post-pelagic
young, becoming low to moderately large rugose tubercles in adults; tubercles raised at various points, above eyes, along shoulder ring with upper tubercle at gill-opening and moderately large lower tubercle positioned ventrally, and those on the trunk mainly enlarged below dorsal fin. Small nape spine present. Adults usually with long dermal filaments on various head spines.
Coronet: Coronet very low with rugose ridges and 2 blunt spines posteriorly in some adult specimens.
Fins: Dorsal-fin base moderately long.
Lateral line: Lateral line pores usually small, but distinct, visible intermittently on tail to about 25^th tail ring.

Colour:

Overall brown, purplish, orange or yellow, sides paler and with black spots; tail blended with paler hues; Tasmanian population with numerous spots on head and trunk; South Australian population with few black spots, often mostly absent from head; Victorian population with variable number of black spots, usually most numerous on head; tail often with pale bands centred on about every 5th ring in dark individuals.

Similar species:

Hippocampus bleekeri is most similar to H. abdominalis from New South Wales and New Zealand, differing in having a larger head, longer snout, better developed spines at all stages, usually with long filaments extending from the head spines. Contention exists as to whether the east coast H. abdominalis is distinctly different from the more southern H. bleekeri. Genetic studies have not found strong evidence supporting more than one species, further research is needed to confirm these findings.

Fisheries:

Specimens are occasionally taken as bycatch in commercial trawls. Captive-bred specimens are reared commercially in a number of States for both the Australian and live individuals are collected as broodstock for aquaculture operations. Both wild caught and aquarium-reared individuals are sold within Australia or exported overseas for the live aquarium trade. Dried specimens are sold in Asia as Traditional Medicine.

Conservation Status:

International: Listed under Appendix II of the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES).
Listed (as a synonym of H. abdominalis) as Data Deficient on the 2008 IUCN Red List of Threatened species.
Australian Government Legislation: Marine Listed under the Federal Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act 1999).
State Government Legislations: Listed as a protected species (as H. abdominalis) in Tasmanian state waters requiring permits for collection (Tasmanian Living Marine Resources Management Act 1995).

Remarks:

The Potbelly Seahorse is easily kept in aquaria if fed regularly on live diet of small shrimp and other crustaceans, especially mysids. The species is somewhat variable in form and colour pattern and further study is needed to determine if populations throughout its distribution represent a single species.

Other common names:

Australian Pot-belly Seahorse, Pot-bellied Seahorse, Southern Potbelly Seahorse, Big-bellied Seahorse, Bigbelly Seahorse.

Original citation:

Hippocampus (Macleayina) bleekeri Fowler 1907, Proc. Acad. Nat. Sci. Philad. 59(3): 426, fig 4, Victoria, Australia.

Etymology:

Hippocampus is from the Greek, ippos = horse and the Greek, kampe = curvature. The specific name bleekeri is after the distinguished Dutch ichthyologist, Pieter Bleeker.

References:

Armstrong, P. 2001. Genetic and Morphological Variation in Pot-bellied Seahorses (Hippocampus abdominalis): Is there evidence for two species? Unpublished B.Sc. (Hons.) thesis, University of Tasmania.

Edgar, G.J. 1997. Australian Marine Life. Reed, Kew, Victoria, Australia, 544 pp.

Fowler, H.W. 1907. A collection of fishes from Victoria Australia. Proc. Acad. Nat. Sci. Phila. 59: 419-444.

Hoese, D.F., D.J. Bray, J.R. Paxton & G.R. Allen. 2006. Fishes. In Beesley, P.L. & A. Wells. (eds.) Zoological catalogue of Australia. Volume 35. ABRS & CSIRO Publishing: Australia, 2178 pp.

Gomon, M.F. & F.J. Neira, 1998. Syngnathidae. In Neira F.J., A.G. Miskiewicz & T. Trnski. Larvae of temperate Australian fishes: laboratory guide for larval fish identification. University of Western Australia press, Nedlands, Western Australia, 474 pp.

Kuiter, R.H. 1993. Coastal Fishes of South-Eastern Australia. Crawford House, Bathurst, NSW, 437 pp.

Kuiter, R.H. 2000. Seahorses, pipefishes and their relatives. TMC Publishing, Chorleywood, UK, 240 pp.

Kuiter, R.H. 2001. Revision of the Australian Seahorse of the genus Hippocampus (Syngnathiformes: Syngnathidae) with descriptions of nine new species. Rec. Aust. Mus. 53: 293-340.

Last, P.R., E.O.G. Scott & F.H. Talbot. 1983. Fishes of Tasmania. Tas. Fisheries Devel. Authority, Hobart, 563 pp.

Martin-Smith, K.M. & A.C.J. Vincent. 2005. Seahorse declines in the Derwent estuary, Tasmania in the absence of fishing pressure. Biological Conservation 123: 533-545.

Martin-Smith, K.M. & A.C.J. Vincent. 2006. Exploitation and trade of Australian seahorses, pipehorses, sea dragons and pipefishes (Family Syngnathidae). Oryx, 40(2): 141-151.

Pogonoski, J.J., D.A. Pollard & J.R. Paxton. 2002. Conservation Overview and Action Plan for Australian Threatened and Potentially Threatened Marine and Estuarine Fishes. Canberra, Environment Australia, 375 pp.

Wilson, A.B. & K.M. Martin-Smith. 2007. Genetic monogamy despite social promiscuity in the pot-bellied seahorse (Hippocampus abdominalis). Molecular Ecology 16(11): 2345-2352.