An obscure world record—we think

Last week Hai and I did a little snorkeling at Kawaihae Harbor. As usual, we started out at the big concrete platforms at the south end of the main harbor where the military ties up its landing craft. There was nothing much to see at the first platform so we moved on. It only took a minute or two at the second platform for Hai to zero in on the biggest Gloomy Nudibranch either of us had ever seen. It was just a few feet below the surface on one of the platform’s support pilings, and we guessed it was about five inches long. We marveled at it for a while, took some photos, and continued on to inspect the rest of the pilings. Soon Hai spotted another similar sized Gloomy, again just a few feet deep on a piling. (I don’t know how he does it—e seems to have a sixth sense  for finding invertebrates. He’s an architect, but he’d have made a great field biologist.) Both Gloomies were actively crawling around, apparently feeding on bryozoans. We took some more pictures, and this time Hai placed his dive scissors next to the nudi in order to establish a size scale.

After we got back to our respective homes we exchanged texts and photos and speculated about the size of these nudibranchs. We also did some research. Hoover, in Hawaii’s Sea Creatures, says that Gloomy Nudibranchs reach about three inches in length. The authoritative and amazingly comprehensive web site, seaslugsofhawaii.com said 76 millimeters (come on, you figure it out). And Keoki Stender’s marinelifephotography.com says four inches. It was obvious to us that the specimens we saw that day were larger than four inches, so Hai took a picture of his dive scissors next to a tape measure so we could use it and his earlier photo to compare tape to scissors to nudibranch. He sent both photos to Dr. Cory Pittman, head honcho of seaslugsofhawaii.com. Cory looked at the photos and proclaimed that our specimen was 121 mm long, a number now reflected on his web site. So we’re calling it a world record.

Here’s the first Gloomy Nudibranch we found that day. Notice the blue-green color of the highlights on the inside of the branchial plume (the gill tuft on the middle of the back).

This is the second Gloomy. Its inner branchial highlights are distinctly more blueish than those of the first individual. Seaslugsofhawaii.com notes that this species is quite variable in coloration, and that the relative abundance of blue versus blue-green specimens has varied quite a lot over the last couple of decades.

Here’s Hai’s photo of the same individual as shown above, with dive scissors for comparison. (The body color here looks a bit different from my photo because I shot without flash—my camera batteries were dying—while Hai used flash.)

Hai got this fantastic closeup of the Gloomy’s “face.” It’s dining on a blue bryozoan, which seaslugsofhawaii.com says constitutes its sole, or at least primary, food source.

My Fivestripe hypothesis

John Hoover calls Fivestripe Wrasses uncommon in Hawaii, John Randall says rare, and Keoki Stender even says they’re “very rare.”  When I first moved to the Big Island in 2009 I tended to agree with at least the first of these assessments. I’d see an individual at Mahukona now and then, but more often than not they were absent from any of the North Kohala sites where I snorkeled. This started changing a few years ago, about when the first warm water coral-bleaching event occurred in Hawaii. Fivestripes have become more common each year since. Now I see them every time I snorkel at Mahukona, and often see them at several other Kohala sites like Hapuna, Pauoa Bay, and Makaiwa Bay. There are almost always a few sub-adults present at Mahukona’s “First Point.”

So, my hypothesis is that the higher water temperatures Hawaii has been experiencing in recent years have conferred a competitive advantage to the Fivestripe over the closely-related Saddle Wrasse. While the Fivestripe Wrasse ranges widely through the tropical and subtropical Indopacific, the Saddle Wrasse is endemic to Hawaii. Within its range the Saddle Wrasse is much more common and lives in a wider variety of habitats than the Fivestripe, which in Hawaii is pretty much restricted to the shallow surge zone. It seems not unreasonable to assume that the two species compete in shared habitats, and that this competition may limit Fivestripe abundance in Hawaii. Maybe warming water favors the Fivestripe, since this species thrives in very warm waters outside Hawaii, while the Saddle Wrasse is restricted to cooler Hawaiian waters. Of course I have no real evidence for this hypothesis, but, as the greatly-missed Tom and Ray Magliozzi would say, post hoc, propter hoc, right?

One of a handful of sub-adult Fivestripe Wrasses that you can find at Mahukona’s “First Point” on any given day.

A handsome initial stage adult at Mahukona. This one may have a few Saddle Wrasse genes—the two species often interbreed.

Here’s a sub-adult photographed in 2018 in Bali, where they’re quite common.

A tough old fish—and a wedding crasher?

Anyone snorkeling out from the dock at Mahukona is likely to quickly encounter a large, reddish-brown fish with a distinctive notch in its back. It’s an Ember Parrotfish, and it’s been patrolling an area near the dock for a few years now. The notch on its back is almost certainly an old, healed spear wound—a not-uncommon sight on Hawaiian reefs.

This one looks like a big old female, but in this case looks may be deceiving. We were talking about this fish with our erudite friend Lori when she informed us that parrotfish may adopt a “stealth male” reproductive strategy. Parrotfish  are usually born as females, with older, more dominant individuals changing sex to become males. The sex change is accompanied by a change from the relatively doughty female coloration to showy male colors. Sometimes though, a parrot will be born as a male but bear female coloration through its life. This allows the individual to infiltrate the harems of nearby dominant males and sneak into spawning events to which it was not invited*. Clever, huh? Anyway, Lori thinks that this fish, whom she’s christened “Chomp” for the notch in its back that resembles a bite mark, is one of these stealth males. She bases this on its size and age—as I’ve mentioned, he/she has been around the Mahukona dock for years. I’m inclined to think she’s right, but who knows. Maybe we should start referring to old Chomp as “they.”

“Chomp,” the big old Ember (AKA Redlip) Parrotfish is often the first large fish you’ll see when you leave the Mahukona swim ladder. She’s usually accompanied by a Christmas Wrasse, presumably tagging along for food scraps. The wrasse took off for this photo, but you can see this type of pairing in the May 15, 2015 and June 18, 2018 posts.

*You can read about this phenomenon here (scroll down to the “Marine Life” heading about a third of the way down the page): https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/parrotfish

Some little guys at Mahukona

We recently returned from a long trip to the mainland and headed straight to Mahukona. The water’s been very clear and the fish have been abundant and cooperative.

Marla spotted this Dwarf Moray swimming out in the open near the “Second Point.” By time I swam over for a look it had retreated into a hole, but it couldn’t resist poking its head out to watch us, and doubtless to check if these giant human ogres had departed. These pretty little eels are fairly common at Mahukona.

There’ve been a lot of Scarface Blennies among the rocks right in front of the Mahukona dock lately. They’re pretty shy, but you can sometimes get a good look at one hunkered in a crevice looking back at you. It’s kind of dark down there, but the flash on my little TG-6 camera did a pretty good job of illuminating this handsome little fellow.

A young Wedgetail Triggerfish, AKA Picasso Triggerfish, AKA Humuhumunukunukuapuaa. These intermediate sized juveniles have been quite common this year. The little ones tend to be a little bolder than the camera-shy adults. Hoover informs us that “nukunukuapuaa” means pig-snout.

A Whitetip checks me out

Yesterday I took advantage of unusually calm conditions to take a long swim from Mahukona to Nishimura Bay, a little-known spot about a half mile to the north. Just short of Nishimura a Whitetip Reef Shark cruised by going in the opposite direction. I turned to follow it and, contrary to to my usual experience with this species, the shark turned toward me and did a circle around me at a distance of maybe fifteen feet. I’ve got to admit that this made me just a bit nervous, but I was confident in my book-learnin’ that unprovoked attacks by Whitetips are vanishingly rare. So I grabbed the little camera out of my pocket and took a few shots—what else would I do? The shark quickly lost interest and swam away in that oh-so-calm manner characteristic of largish sharks, leaving me stoked.

The Whitetip giving me the eye. A lot of spearfishing goes on in this area, and it could be that this fellow, about five feet long, was wondering if I happened to have a stringer of recently speared fish that it could snatch. I’ve read that the pattern of dark spots on the flanks can be used to identify individual sharks.

More cleaners—and happy New Year

I’ve been spending more and more time at the close-in Cleaner Wrasse station at Mahukona. It’s great fun watching the complex interactions between cleaners and cleanees, as well as among the cleanees. There’s a lot of jockeying for position and chasing. The posing fish are clearly eager for the wrasses’ attention, expecting to have a parasite or excess bit of mucus removed. But the little cleaners often double-cross the cleanees by taking a bite of living skin, to the subject’s obvious annoyance. From earlier this month:

Manybar Goatfish posing for cleaning. The reddish color they’ve assumed here is also their typical night coloration. Many species of reef fish turn reddish at night. Look at those extended barbels.

A Manybar Goatfish showing its normal daytime colors. (From 2017.)

Away from prying eyes

When snorkeling or diving we routinely look deep down among the branches of any cauliflower or antler coral we pass. You never know what you’ll find in there—these corals (what’s left of them after the 2014-2015 bleaching event) provide shelter to a wide variety of fish and invertebrates. I posted a photo of a guard crab hiding in an antler coral back in June. Here’s what we saw yesterday in a cauliflower coral at Mahukona:

A Speckled Scorpionfish peering back at the camera. This common endemic is, according to Hoover, one of several scorpionfish that inhabit branching corals in Hawaii. While we see Speckled Scorpions quite frequently, they usually present a side view or tail view to to the camera (see my November 25, 2016 post), so I was pleased to get this head shot. This fish was about two inches long in water about ten feet deep.

This Hawaiian Coral Croucher was hiding even deeper in the same coral head. Fairly common, but notoriously hard to photograph, these shy endemics are related to scorpionfish. The velvety appearance of the skin is a distinctive characteristic of this family—Caracanthidae. About two inches long.