In 2016, Oak Bluffs Shellfish Constable Dave Grunden and Woods Hole Oceanographic Institute (WHOI) biologists Mary Carman and Annette Govindarajan set out to study sea squirts in Farm Pond.
But with the sea squirt population dramatically down from 2015, the biologists turned their focus to the rapidly growing Gonionemus, or clinger jellyfish. The diminutive jellyfish packs a knee-buckling wallop and has gained a foothold in several Island ponds in recent years.
Mr. Grunden said the results of the year long study — published on Oct. 26 in PeerJ, a journal covering research in medicine and biology — surprised the group.
They found that spider crabs (Libinia dubia) voraciously consume clingers, up to 30 in a 24-hour period in a controlled situation.
This also turns out to be their last meal.
“One hundred percent of spider crabs tested died within 24 hours of consuming jellyfish in our maximum jellyfish density containers,” the study states.
“We tested them with 10, and 15 jellyfish and none died, but once they ate over 20 or so, they started to die,” Mr. Grunden told The Times. “They consume them voraciously when they have the opportunity.”
Since spider crabs are exposed to a much larger clinger population in the wild, clingers could cause a decrease in the spider crab population.
On the other hand, the study found that the invasive green crab (Carcinus maenus), steered clear of clingers.
“Carcinus populations could be indirectly benefiting from this unusual crab–jellyfish trophic relationship,” the study concludes.
Mr. Grunden said the green crab has been in Vineyard waters since about 1850.
“I wouldn’t call this study groundbreaking, but it certainly means we should take a closer look at the [clingers] in the coming years,” Mr. Grunden said. “The other big question is where they come from.”
This study was funded by grants from the Oak Bluffs Community Preservation Committee, the USGS-WHOI Cooperative Program, the Adelaide M. and Charles B. Link Foundation, and the Kathleen M. and Peter E. Naktenis Family Foundation.