2016 Mayne Island Eelgrass Survey

Mon 21 November 2016 by Tom Lightfoot

On the weekend of July 23-24, the Vancouver Apneist Freediving Club helped to survey the eelgrass beds of Gallagher Bay, Mayne Island. This is the eighth year that the club has been helping the Mayne Island Conservancy to map the island's eelgrass beds.

Eelgrass is an important habitat for many fish and invertebrate species. It also is an important carbon sink and also works to reduce ocean acidification.

The dive club's role in the surveys is to be the 'eyes on the ground' to help map out the location of the grass bed, most importantly, the deeper subtidal edge that can't be seen from the surface. We have partners in kayaks to record our positions with a GPS as well as our reported depth and bottom substrate. The end product is an outline of the grass bed as well as qualitative information about its health.

We have taken part in some more rigorous data collection involving, setting up transects along the middle of the bed and counting shoots per square metre in quadrats (square frames) that we set on the bottom. However, this proved to be quite a challenge for breath-hold divers in poor visibility and strong current. Mapping is definitely our forte and we largely stick to that.

Over the past eight years the Mayne Island Conservancy has built a long term data set to see trends in Gallagher Bay, Horton Bay and Miners Bay. In Gallagher Bay we were able to detect a reduction in the shallow part of the grass bed, possibly due to feeding by Canada geese. There was also a new gap in front of the big rock in the middle of the bay. Shaw Cable has installed a cable through the bay since our last survey and we did see it. However, we didn't see it running through the gap and there was no obvious sign of disturbance.

Here are some links to some video transects that I took for Leanna:

From Saturday the 23rd:

From Sunday the 24th: