Aurelia swarm

Description and Comments

A swarm of Aurelia (moon jellies) spotted at the mouth of Matheson Inlet beyond (E) of the shallow sill that marks the entrance of the inlet. This is in Juan Perez Sound in southern Haida Gwaii.

It was a bright strip in the water that appeared at first to be an uncharted sand bar with clam shells on it, or similar brighter spots. It was considerably longer than our 70 foot boat - two or three boat lengths at least. It was located a couple of feet below the surface below a layer of brownish water that is mixed with local creek outflows. The thickness of the swarm is unclear - at least 2m deep I would guess. The width was at least 10 or 15m.

We watched it from 1:20 to 1:30 pm. The swarm became less visible and then more visible over the course of our watching it.

We put a camera in the water and video can be found at and you can see that there were many thousands of moon jellies packed so tight that they are often touching each other. There are more photos from above water at

It should be noted that in this area (east coast of Gwaii Haanas generally) that jellies are ubiquitous including many many Cyanea and Aurelia - this includes in the protected waters and along more exposed shorelines of Hecate Strait. I have not seen more jellies in the water anywhere else and I grew up from the early 1960s spending summers at the Friday Harbor marine station where my father worked as a jellyfish biologist and I collected jellies for pennies to assist various researchers. Also, I have worked on the water in small boats in British Columbia since the mid 70s, including the west and east coasts of Vancouver Island, the north coast of BC and many times in Haida Gwaii. This is the first time I have seen a swarm.


Type of organism