Life at the Antler Coral Colony

This antler coral (Pocillopora grandis) was damaged in July 2025. I wrote about the possible cause, the relocation of its parts, and some good news about its recovery here. However, that was just dry information.

I’ve visited this colony for years, regularly watching the residents live and hide among its branches. Seeing the same familiar species repeatedly can create a one-sided relationship. I looked forward to seeing them, but to them, I was probably just a bother. I want to share some insights about life in this community, which was home to a wide variety of species. 

The main residents and builders of this dome-shaped city are polyps. These animals have constructed tall structures that resemble antlers, extending outward and upward. The spaces between the branches resemble streets and alleys, creating an ideal habitat for species adapted to living in coral. Some of these species are temporary residents, while others prefer the antler coral colonies. Among the few rare species found here is the Speckled Scorpionfish (Sebastapistes coniorta), native to Hawaii and currently listed as Near Threatened (NT) on the IUCN Red List.

On the day I arrived, I saw that nearly half of it had been severed. A single branch of antler coral, measuring 10 cm long, can support over 6,000 polyps. Almost half of the colony broke away, with many branches reaching up to 30 cm or about a foot tall. The population of the broken parts could be in the hundreds of thousands. For comparison, my town has only about 2,300 residents. When a coral colony is damaged, it’s like a neighborhood in a city being destroyed. Fortunately, the polyps in the fragments sometimes survive. Corals are somewhat resilient, but they also remain vulnerable.

The Speckled Scorpionfish occupied the damaged area from August 2024 to April 2025. It consistently remained in the same spot during each visit. This area also hosted a few Marbled Shrimps from May 2023 to June 2024.

Elsewhere on the colony, there were more notable species, such as the Starry Coral shrimp (Harpiliopsis beaupresii) and the Flattened Coral Shrimp (Harpiliopsis depressa).

This colony will always be my favorite whenever I dive here. It feels like visiting friends. My desire to see more antler coral colonies motivated me to collect the broken pieces and relocate them to another area.

I failed despite my sincere efforts. The relocated branches are struggling to survive, as shown here. There is a glimmer of hope because small patches of polyps have managed to survive. Moving the parts (Antler Coral Parts 1) just ten meters to a more exposed location, where there is more direct sunlight and stronger currents, may have added more stress that these animals could not handle. 

 I previously successfully saved another damaged antler coral colony (Antler Coral 2) here. Do differences in location and exposure affect their ability to survive and recover? (Plant cuttings usually do better in partial shade during rooting.) One set of relocated corals thrived and grew 2.5 cm over 6 months, while the other barely survived. The main differences between the two are the location, the time of year, and water temperatures, which are 77.7°F in March and 80.1°F in July and August.

We will monitor how the relocated pieces recover, and we all hope they will rebuild. Many factors affect how corals survive, recover, and thrive. Based on my observations, I believe they will rebuild fairly quickly in the favorable environment of Kawaihae Harbor.