Research from over a decade ago pointed to the possibility that, with rising global temperatures, an increasing human population and rampant overfishing, jellyfish were positioned to take over as a dominant inhabitant of the world’s oceans.
But proving that hypothesis has been tricky, and some in the scientific community say there’s not presently enough evidence.
First of all, there’s a lack of baseline scientific data. For many years, and in most parts of the world, jellyfish were regarded as a nuisance, clogging fishing nets, power plant intake pipes and beloved scenic shorelines. They were not valued as something to be counted, quantified or even monitored.
Secondly, the lifecycle of most jellyfish is not well understood. These creatures are known to arrive in blooms – populations can boom and bust over a period of years leading to the possibility that, anecdotally, it may appear that there are more of these creatures in the water than in previous years — and that may well be the case — but that doesn’t mean the overall long-term population trajectory is upwards.
A new report from the University of British Columbia’s Fisheries Center seems to show an overall increase, globally, in jellyfish populations. The report looked at Large Marine Ecosystems, or LMEs, around the world (of which there are 66 total). For example, the Gulf of Alaska is one LME, the California Current that moves along the Northwest coast is another. Lucas Brotz, the lead author on the paper and a PhD candidate at UBC, combined scientific data with anecdotal evidence collected from 45 of those 66 LMEs and found an increase in jellyfish populations in 62 percent of them.
Here are the hotspots for jellyfish population increases, according to a new report by the University of British Columbia:
“Really this is the first study to incorporate anecdotal data in addition to the scientific data,” Brotz says. “Other scientists have said we don’t have the evidence to say that jellyfish are increasing globally but that was based on quantitative data sets.” Brotz views anecdotal evidence, which he collected from fishers and biologists in all the various LMEs, as a necessary means to uncover the overall trend in jellyfish populations, given the lack of baseline or historic data.
But, he cautions, “only one third of our conclusions were of high confidence so this sort of still underlines the fact that in most of the areas we still don’t know that much about the jellyfish populations and it’s high time we started paying more attention to them.”
Scientists aren’t sure what might be causing the increase in jellyfish populations in certain parts of the world, but Brotz believes humans play a role.
“This certainly isn’t the trend across the board but when we look at all the systems we studied there seems to be a theme that’s emerging where areas that are highly affected by coastal development, pollution, overfishing are often areas that show increased jellyfish populations.”
Brotz also sited invasive species of jellyfish as contributors to some of the evident increases in the local jellyfish populations.
As for the Northwest? Brotz says the data is less conclusive here. We straddle two LMEs – the Gulf of Alaska ecosystem and the California Current ecosystem. The Gulf of Alaska appears to be stable, according to Brotz, but down along the Northwest coast he says it does look like populations of jellyfish may be increasing but “we don’t have high confidence to say that.”
And perhaps he shouldn’t. Dr. Claudia Mills is a researcher at the University of Washington’s Friday Harbor Labs on San Juan Island. She has been monitoring populations of about 60 species of small jellyfish in Friday Harbor for the past 35 years. She has not published any peer reviewed research on her findings, but, from what she’s seeing in small jellyfish, the population has decreased over the past several decades and there’s less species diversity.
“The main characters have shifted substantially during that 40 years,” Mills says, “so the ones that were most common during the 70’s and 80’s are now relatively uncommon.”
Mills says anecdotal data can be incredibly valuable in studying often-overlooked creatures like jellyfish, but that researchers need to be careful.
“A lot of lay people won’t know what they’re seeing, but if you can tease it out there’s certainly information and in terms of historic information it’s the only thing you’re going to have.” But, she says, “How you use it is pretty tricky.”
A video about jellyfish, courtesy of the Monterey Bay Aquarium.
Congrats to David James for his winning submission, 'Annabella smelling the Balsam.'
Share your experiences as part of EarthFix's Public Insight Network.
Join our Public Insight Network!