Division of Aquatic Resources

Upon my first step into Heʻeia fish pond, the soft mud swallows my boot well past the ankle; the suction would have surely pulled it off my foot, had it not been attached to thick wader overalls that kept the waist-deep waters from soaking my clothes.  Like my legs, my hands were sheathed in rubber gloves with sleeves that ran past my elbows, but these were not to keep the water out…they were for the stings.

Ahead of me, my prey appeared: a pulsing kaleidoscope of orange and green, disturbed by the movements of those ahead of me.  Drawing from childhood fishing experience, I gripped the scoop net in my hand and struck, bagging the first of many catches that day.  This was not how you typically harvested in Heʻeia, but then again, this was not your typical catch.  We weren’t fishing; we were jellyfishing.

Conservation is a community effort, and jellyfishing is always more fun with more friends.

An Accidental Arrival

Cassiopea or Upside-down Jellyfish as they are known, were accidentally introduced to the Hawaiian Islands when they were brought in the bowels of ship ballast tanks.  Like their cousins the coral, they are able to photosynthesize–create food from sunlight by lying upside down in the mud, with their tentacles pulling extra food from the water column.  In the calm lagoons and fishponds of Hawaii, they absolutely thrived.

Upsidedown jellyfish cover the shallow bottoms of the fish pond. At least three species are believed to be in Hawaii.

This was how Heʻeia suddenly found itself faced with another invasive species, as the conditions that allowed mangroves to flourish also benefited the upside-down jellies.  Thousands of them quickly outcompeted the stocks of opae and mullet that Heʻeia’s caretakers worked so hard to cultivate.  It had been hard and laborious, but Heʻeia had successfully removed the mangroves and they would remove the jellies too.  And they wouldn’t be alone.

Netting the Cnidarians

The call was answered by some fifty volunteers and staff.  DAR Watershed Restoration Coordinator Anthony Olegario invited fellow staff and our Invasive Species Team to partake in the effort.  While Heʻeia’s caretakers have had previous jelly removal days, this was the first time that the call went out and in total, an estimated 20% of the jellyfish were removed from the fish pond.  Not bad for a first time.  

Workshopping Solutions

Upsidedown jellyfish are capable of releasing “sting grenades” that allow them to push out other species and take over fish ponds.

An indirect benefit of such a large gathering was that it gave us an opportunity to exchange ideas on how to effectively tackle the situation.  Scoop netting was effective, but time-consuming.  Some volunteers imagined a smaller version of the super sucker vacuum that had removed seaweed from Kaneohe Bay, while others commented that in past removals, visiting honu may have helped control the jellies by eating them, and bio-control may be an effective long-term solution.  For the time being, scooping the jellies appears to be effective, but future gatherings may further flesh out ideas that can permanently keep Heʻeia free of these pulsating pests.

Conservation is a community effort and the greater number of volunteers, the greater the impact. Heʻeia plans to host jellyfish removal every other week and eager participants are always welcome.  https://paepaeoheeia.org/volunteer/Not only is jellyfishing a fun way to talk story and swap ideas, but it also provides greater insight into traditional aquaculture while contributing to the stewardship our aquatic resources.

Charles Lee – Education Specialist, O‘ahu