Jellyfish populations are on the rise


Lucas Brotz dives with a lion’s mane jellyfish
Photo by Conor McCracken

Adapted from The Vancouver Sun

Level 2

Some are bigger than a person.
Others are as small as the head of a pin.
They have no brain.  But some have eyes.
They eat small plants, fish eggs and small fish.
Most of them live for less than a year.
Some of the smallest live only a few days.
Their home is in the ocean.
A group of them is called a “smack”.
They have been on Earth for millions of years.
They were on Earth before the dinosaurs.
What are they? They are jellyfish.

A study about jellyfish
Jellyfish are increasing in most of the world.
University of B.C. (UBC) researchers want to know why.
Lucas Brotz says this is the first study
which looks at jellyfish all over the world.
Brotz is a PhD student with the Sea Around Us Project at UBC.

Possible reasons
Daniel Pauly also works on the jellyfish study.
He thinks there are more people near the jellyfish habitats.
People cause pollution.  Pollution means more jellyfish.
Pollution harms some sea life.  But jellyfish seem to like pollution.
Too much fishing might also be a reason.
The warming of the ocean might be another reason.

What people think of jellyfish
Many people think jellyfish are a nuisance.
Jellyfish sting swimmers.
These animals get into boat engines.
They also stop fishermen from getting their fish easily.
In some countries people eat jellyfish.


Giant jellyfish interfere with fishing in Japan.
Photo by Shin-ichi Uye

Jellyfish are useful
Jellyfish are very important animals in the ocean.
People should respect them.
And people should not harm them.  Why?
Large fish and turtles eat jellyfish.
Some small fish hide under jellyfish.  Then they are safe.
Many young crabs hitchhike on jellyfish.
They get free rides on the top of the jellyfish.

What can we do?
We can help clean up the ocean.
And count any jellyfish we see when we are out.
Then report the number to


A bloom of moon jellyfish in Denmark.
Photo by Casper Tybjerglmost