Decadal shift in Lion's Mane Jellies (Cyanea capillata) on Nova Scotia's North Shore

Observation: I grew up in Pictou County in northern Nova Scotia. I spent many summer days swimming at Melmerby Beach and Caribou Beach on the south shore of the eastern Northumberland Strait (Figure 2). Little swimming occurred during the first month of summer as there were too many jellyfish, specifically lion’s mane jellyfish (Cyanea capillata; Figure 1), for swimming to be enjoyable. By the end of July, most of the jellyfish were gone. Over the past approximately 10 years, I have noticed a gradual decrease of the numbers of jellyfish in the nearshore area of these beaches in the early summer.

When I was young, I asked adult relatives why the jellyfish were present in the early summer and then disappeared. I was told that they come inshore in the early summer when the water is still cool, but move away from shore as the water warms up during the summer. I believe that the water in the Northumberland Strait is getting warmer due to climate change and this causes the jellyfish to move inshore earlier and leave earlier in the season or not move inshore at all. - Amanda Facey, Royal Roads University, Canada.

Comment by LEO BC Coordinator, Tom Okey: This is a very interesting observation, especially given the long-term nature of the personal observations and information gleaned from elders with local knowledge. Amanda Facey's theory makes sense given that this species is confined to cold boreal waters. The average global sea surface temperature has indeed increased ~1° Celsius since 1980, and ~2°C since 1910 (Figure 3), but the waters around Nova Scotia have increased much more than the global average, such as up to 4°C (see Figure 4). - Tom Okey, Ocean Integrity Research and the University of Victoria, Canada.

Resources:

Lion's mane jellyfish on Wikipedia