Summer Series 1: You might fall in love this summer, with a sea monster

This summer, watch out when snorkelling around the New Zealand coastline, for our very own sea monster: Hippocampus abdominalis, the pot-bellied sea horse.

This summer, watch out when snorkelling around the New Zealand coastline, for our very own sea monster: Hippocampus abdominalis, the pot-bellied sea horse.

 “Fully grown sea horses can be found at a depth of 5–10 metres, often amongst seaweeds, and are most active at dawn or dusk.  They’re not fast swimmers – in fact people are faster”, says Dr Chris Woods, a scientist with NIWA’s Marine Ecology and Aquaculture group in Christchurch.

 All sea horses belong to the genus Hippocampus, (from the Greek hippos, meaning horse and campus, meaning sea monster). Of the 38 known species of sea horse worldwide, New Zealand has one of the largest.  

 Sea horses propel themselves by using a small fin on their back that flutters and fins on the head which steer it. The sea horse has a big belly and leathery armour-like skin.

 Courtship and reproduction in sea horses is elaborate, involving changing colour and much posturing. The male and female repeatedly approach each other with their heads tucked down and dorsal fins rapidly fluttering. A series of short tandem swimming bursts then follow, with tails entwined.

 Either sex then encourages the other to swim towards the surface by repeatedly pointing its snout upwards. If the other responds in the same way, the final stage of courtship begins. Both sexes swim upwards, with their heads pointed upwards and tails straight down. For egg transfer, the female faces the male, and they spiral together. Pressing the base of her abdomen against the male’s opened pouch, the female squirts her eggs into the male’s pouch to be fertilised. Then the two return to the safety of the seaweed and dull their colours, and it’s the male who bears the developing young.

 If you’re face-to-face with sea horses this summer, remember don’t touch them, just admire these beautiful creatures from afar.

Scientist bio:

Dr Chris Woods worked in sea horse aquaculture for nine years at NIWA. His current research focuses on developing sustainable and effective aquaculture species opportunities and culture practices; and marine biosecurity, specifically: assisting with preventing, detecting, and responding to incursions of non-indigenous marine species in New Zealand. “What I enjoy most about the work that I do is, firstly, having the opportunity to study and understand our fascinating and varied marine biota, and secondly, working with a great group of talented and enthusiastic colleagues.”

Species Fact file

Sea horse

Common Name:

Large-bellied or pot bellied sea horse

Māori Name:


Scientific name:

Hippocampus abdominalis


Bony fish




Small crustaceans such as shrimp and amphipods


5–10 years


Up to 30–35 cm in length

Things you need to know:

The sea horse sucks in its prey through an elongated snout. They have no teeth or stomach.

Something strange:

Their eyes move independently of each other.


The male receives the eggs from the female and, after fertilisation broods them in a pouch until they are released.