After our two wonderful days at Midway Atoll, we headed further northwest to the furthest northwest point in the Hawaiian Archipelago: Kure Atoll. We first visited here on our NOAA deep diving cruises back in 2009. At the time, we were limited to a maximum depth of about 200 feet (60 m), and the bathymetry data we had was very limited, so we ended up doing a series of dives in very boring sites. Because of this, we were never very enthusiastic about going back there. That is, until last year. With our depth range extended to 300 feet (90 m), and with much better bathymetry data in hand, we were able to conduct a series of spectacular dives that led to a major scientific discovery: the highest documented rate of marine endemism on Earth!
Five separate surveys conducted at five different sites yielded 100% endemic species. That is, every single fish counted in the survey transects was a species found only in the Hawaiian Islands. The timing of our visit this year was perfect, as it came just on the heels of our publication on this incredible discovery. Our surveys this year extended the dataset, with the same result: all endemic species on deep reefs at Kure. This is truly remarkable, and underscores how unique the reef communities of this Monument are.
Many of the endemic species we encountered were extremely abundant. For example, Struhsaker’s Damselfish (Chromis struhsakeri) — a species found only in much deeper waters in the Main Hawaiian Islands, were scattered over the reef by the thousands. We noticed many more juveniles and subadults of this species than in previous years, which suggests a particularly good recruitment. We also saw large schools of Elegant Anthias (Caprodon unicolor) and Hawaiian Pigfish (Bodianus bathycapros) — species that are almost never encountered by divers. In fact, until our expedition here in 2014, the male of the species had not been well documented.
Another unusual fish we’ve seen here on previous expeditions is more abundant this year than in the past. It’s a wrasse in the genus Suezichthys, which is very similar to a species known from the western Pacific (S. arquatus), but differs in several respects. We’re still studying this fish to determine exactly what it is.
And, of course, fishes are only part of the story. On two separate dives this year, the team encountered a very unusual (and large) benthic ctenophore. This group of organisms is very poorly known, and in bad need of further taxonomic study. Until that happens, we’re not quite sure what species this is, but it’s certainly unusual here in the Hawaiian Islands.
Furthering the “Kure-osities” on this expedition, the deep team had an extremely unusual encounter with an Oceanic Whitetip shark (Carcharhinus longimanus) during their surveys. This species typically inhabits open ocean environments, and is rarely encountered on or near a reef. Although it was fairly large and came in for a close look, it didn’t hang around long.
Another extraordinary discovery at Kure actually happened aboard the ship at night. Several days ago, we brought up an unusual post-larval fish that was hiding among the spines of a sea urchin collected at about 200 feet (60 m) deep off Maro Reef. In the bucket where we were keeping the larvae alive, we found a very young Hawaiian Grouper (Hapu’u; Hyporthodus quernus) and no post-larval fish. At first we assumed that someone had caught the grouper, and it ate the little transparent post-larval fish; but then we suddenly realized it was the same fish! In a matter of just a few days, it had completely transformed!
But by far the most exciting discovery we made at Kure Atoll this year happened near the end of my second day of diving. While scanning the reef, something caught my eye. Among the thousands of small Thompson’s Anthias (Pseudanthias thompsoni) that dominate these reefs, I noticed one that seemed to have a small parasite affixed to its posterior. On closer inspection, I realized that what I had thought was a parasite was actually a spot on the dorsal fin. Thompson’s Anthias have no such spot, nor does any other known anthiine species that lives anywhere near Hawai’i. I managed to get a few short video clips, then at the end of the dive was finally able to collect it.
That afternoon, Brian Greene spent his entire dive scouring the reef looking for more, but found none. The more we look at this fish, the more certain we are that it represents a new species. But is it a juvenile? An adult male? Female? Later on, while watching the video I took, I noticed a second, smaller one dart into the same hole. Based on the size and color, we guessed it was probably the female. The next day we headed for Pearl and Hermes Atoll, so we thought we wouldn’t have another chance to find it again. However, on his dive at Pearl and Hermes, Brian found three more (one male and two females), and managed to collect one of the females. We’re now almost certain that it represents a new species, and we will of course be carefully inspecting these deep reefs for more specimens.
Although I didn’t find any of these mystery Anthias on my dive at Pearl and Hermes, I did managed to collect three specimens of an undescribed butterflyfish in the genus Prognathodes. We’ve known about this fish for years, but only just recently got the specimens we need to formally describe it as a new species. One very peculiar characteristic of this fish is that we almost always find it in groups of three. I’m not aware of any other fish species that maintains such a consistent ménage à trois, so it’s quite unusual in that respect. So many things to discover!