BIG BELLIED SEAHORSE
Article by Sarah Dunn
strong and steady
The Big-bellied Seahorse (Hippocampus abdominalis) is one of the largest seahorse species in the world, reaching up to 35 cm in length. Recognisable by its yellow colouration and pronounced belly, it belongs to the Syngnathidae family, which also includes seadragons and pipefish. Unlike other seahorses, the Big-bellied Seahorse is a relatively strong swimmer, capable of travelling hundreds of metres per day, albeit at a slow pace.
diverse distribution
The Big-bellied Seahorse is distributed from Newcastle in New South Wales across to the northern Great Australian Bight, as well as in Tasmania and New Zealand. It inhabits waters ranging in temperature from 8℃ to 24℃, demonstrating its adaptability. These seahorses are typically found in sheltered areas, often in deeper waters up to 50 metres, though they have also been observed in shallow intertidal pools.
Image: Jeff Bowey
isolated observations
Port Augusta, located in the Upper Spencer Gulf, represents one of the most northwestern points in Australia where Big-bellied Seahorses have been found. This area is characterised by extreme environmental conditions, including high salinity, significant temperature variation, and fast-moving tides.
Despite these harsh conditions, Big-bellied Seahorses have been observed, particularly around artificial structures such as discarded shopping trolleys and tyres. These objects, typically pollutants, have become substrates for sponges and algae, creating unexpected habitats for seahorses and contributing to the biodiversity of the area. This adaptability highlights both the resilience of the Big-bellied Seahorse and the potential productivity of artificial reefs within the Great Southern Reef.
HABITAT HIDEOUTS
This seahorse species thrives in a variety of habitats, including natural reefs and artificial structures like jetties and nets. They are commonly found among macroalgae, seagrass, rocks, and sponges. The Big-bellied Seahorse uses its tail to anchor itself to these structures, blending into its surroundings to evade predators. Their colouration ranges from white and yellow to brown, often with darker spots on the head and trunk, providing effective camouflage. Notably, they are frequently found in abundance around artificial structures, likely due to the substrate these structures provide for sponges and algae, offering additional hiding places.
hunting strategy
As ambush predators, Big-bellied Seahorses rely on camouflage to hunt. They use their vision to detect prey, striking when it comes within close range. Without teeth, they use suction to ingest their prey whole, primarily feeding on small crustaceans such as amphipods and shrimp. Natural predators of the big bellied seahorse in the Great Southern Reef include flathead, Australian salmon, various bird species, and little penguins.
REPRODUCTION ROLE-REVERSAL
One of the most fascinating aspects of seahorses is the phenomenon of male pregnancy. Like other seahorse species, female big bellied seahorses transfer eggs to the males, who then fertilise and carry the young until they are born. Pregnancy lasts from 9 to 30 days, after which the male gives birth to live young that are independent from birth.
Image: Merv Dannefaerd
Fast Facts:
Species: Seriola lalandi
Species: Hippocampus abdominalis
Family: Syngnathidae
Order: Syngnathiformes
Feeding: Small crustaceans
Habitat: Hiding amongst Algae, sponges, rocky reef, artificial reef 🪸
Distribution: Newcastle NSW, Vic to as far west as the northern Great Australian Bight in South Australia, Tasmania and New Zealand
Size: Up to 35cm
