Sea urchins, kina, are an important species ecologically and culturally. However, these kelp munchers can sometimes be misunderstood - get to know them a bit better through the resources below!
Q. Kia ora Kina! Can you tell us a bit about yourself?
A. I’m the most common sea urchin species in New Zealand! I am an endemic species, which means I am only found in New Zealand waters. My round shell encases my internal organs and is covered with movable spines of varying lengths and between the spines are small tube feet which help me get around. At first glance, it’s might be hard to see, but urchins are related to starfish! We belong to a large group of animals referred to as Echinoderms, which translates to ‘spiny skin.'
Q. Where do you call home?
A. You can find us on the rocky shore and in shallow waters up to 15 meters deep We thrive in relatively shallow ecosystems where there is kelp to eat. Kina are found in many areas across the country, from the Three Kings Islands in the north to the Snares Islands in the south, and around our offshore islands.
Q. We’ve heard you’ve got a talent for blending into your environment, how do you do it?
A. Yes, we’re quite good at hiding! We use our tube feet to hold on to pieces of algae, shells, or anything else we can find to shelter ourselves. This behaviour is known as “hatting.” It helps us blend into our surroundings and avoid being eaten by large crayfish or snapper.
Q. What do you typically eat?
A. We are primarily herbivores, particularly fond of large brown seaweeds, but occasionally eat other organisms. Our favourite food is the common kelp, Ecklonia radiata. Our mouths are located on our underside, where we have a five-sided structure which works like jaws and teeth to grind up food. This mouth like structure, called an Aristotle’s lantern, can grow up to 1.8 cm in diameter! We are nocturnal, which means we eat throughout the night, scraping and gnawing at algae on rocks.
Q. How do you reproduce?
A. Every year from November to March, female Kina release tonnes of eggs in a process called broadcast spawning. The eggs drift in the water until they are fertilised by the sperm from a nearby male. Once they have hatched, the larvae spend around 5 weeks eating microscopic plankton, before they land on the seafloor and develop a hard shell, called a test. The life span of a kina can be 20 years or more, with kina reaching 150-200mm in size.
Q. What role do you play in the ecosystem?
A. We are an indicator species meaning that our population density can reflect if something is not quite right in our ecosystem. Since we feed on kelp and other algae, we help control the growth of these algal species and maintain the balance of the reef ecosystem. However, if our numbers get out of control due to the overfishing of our predators like crayfish and snapper, it can lead to overpopulation of kina.
Overpopulation leads to overgrazing, creating what’s known as a ‘kina barren’ - where the urchin population is very dense and the reef is stripped bare of algae. This can have significant negative impacts on the entire ecosystem. Protecting our habitats and ensuring sustainable fishing practices helps to maintain a balanced ecosystem.
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