Wai'opae pools

Wai'opae pools among basalt bedrock and boulders.

The Big Island has about 6 Marine Life Conservation Districts, marine reserves established by the state of Hawaii that variously protect coastal marine organisms from harvest. A short stretch of coastline containing the Wai’opae pools is the only MLCD on the eastern end of the island. The site is southeast of Hilo, near the town of Kapoho, tucked behind a few coastal residences.

At Wai’opae the dark lava is spread in a wide flat bench that creates a broad area of pools between emergent rocks. Some of the pools are shallow and might be properly considered “tide pools”, but others are deeper and create permanent subtidal habitat. Partly isolated from each other, each pool is a small reef ecosystem.

Purple ember parrotfish, Scarus rubroviolaceus followed by an endemic saddle wrasse, Thalassoma duperrey among convict tangs.

Closeup of coral polyps.

 Saturday I spent several hours exploring five pools, ranging in size, depth and species composition. My son Ben located the first, a deep pool with a few corals and a moderate number of fish located far inshore from the breaking waves off shore.

Later I spent a little time in a round pool not wider than 5 or so few meters across, with black basalt enclosing a cozy aquarium. One side of the pool was shallow, the other deep, but each with a number of brown plate corals. The colonies of this species form rounded shelves against the rocks like shelf fungi that grow on trees or fallen logs in a temperate forest.

The last pool I explored was the largest and had the most obvious active connection to the ocean, indicated by a strong current present at the southeastern end. I was already cold at this point in the afternoon, but I probably ended up staying another hour in this pool. The axis of the pool was like a shallow V-shaped valley, along which I swam back and forth several times. Fish abundance in the pool was remarkable, and included wrasses, butterflyfish, large purple and greenish parrotfish, and a dense school of striped convict fish accompanied by several large black colored fish that swam with their smaller associates. Blue needle fish were common in the surface water, creating a ring around me, but keeping some distance.

Unidentified blenny perched in coral in a shallow pool.

The pools I observed did not have continuous coral cover. In fact, at some had just a few percent cover. Rather, corals appeared as discreet colonies, with bedrock, volcanic rubble, or fuzzy algal turfs occupying the rest of the space. They seemed absent from the shallowest areas, perhaps because these are exposed a low tides. Lobe (Porites sp.), lace, and plate corals were common. In the pools I found few species of larger macroalgae, but notable exceptions were a single siphonous green alga (?Caulerpa sp.) shaped not unlike an immature bunch of green grapes, and dichotomously branched thin blades of an attractive red foliose alga. Larger invertebrates included beautiful slate pencil urchins and two species of holothuroideans (sea cucumbers).

A school of convict fish.

Green siphonous macroalga, perhaps Caulerpa sp.

Plate coral.

Needlefishes swimming near the water surface.

Hawaiian whitespotted toby, Canthigaster jactator.

The common saddle wrasse, Thalassoma duperrey. Many wrasses change sex over
the course of life. This fish is an "early stage" male or female. "Supermales" have a
white vertical mark behind the reddish band.

References

Hoover JP. 2014. Hawai’i’s Fishes. A Guide for Snorkelers and Divers. 2^nd ed. Mutual Publishing, Honolulu.

Krupp D. 2010. Hawaiian Coral Index Page: http://krupp.wcc.hawaii.edu/BIOL200/hawcoral/corindex.htm

Mahaney C, Witte A. 1993. Hawaiian Reef Fish. Blue Kirio Publishing.

Honaunau Bay

Our first two full days on the Big Island provided a chance for beach exploration on the south Kona coast. To snorkel I originally wanted to visit Kealakekua Bay, a marine life conservation district (state marine reserve), but the only public road led to the southern part of the Bay where the swell was probably too significant for the kids to venture much into the water. Honaunau Bay to the south became an excellent alternate location, and I the reef were enjoyable enough to return for a second day.

Slate pencil urchins, Heterocentrutus mammillatus.

The Bay is located just north of a small National Historic Park and seems to be a popular tourist location. Many bobbing snorkelers notwithstanding, the fringing coral reef that hugs the shore was teeming with biological activity. Most human visitors stayed close to home base and it was easy to get away from the crowds by venturing a bit north just offshore. The reefs gradually descended offshore, to depths of probably at least 50 feet. Bright yellow tangs and many other species were abundant in shallow water, so it was easy to see quite a few fish species in only 10-20 feet deep.

Corals comprising the reefs came in various shapes, mostly as massive plates, and some were bleached. The most abundant motile invertebrates may have been urchins, or at least this was the taxonomic group that caught my eye. Pencil urchins with their brick red cumbersome spines were tucked into crevices in the complex reef, while large black urchins with full arrays of thin quill-like spines ventured out in the open, cognizant that no other reef creatures would be likely to interfere with their activities.

The fish were most impressive, occurring in abundance, busily tending to the business of reef life. Bright yellow tangs, in groups or large schools were probably most common. Other groups included butterfly fishes, flamboyant Moorish idols, triggerfish and parrotfishes. There was some chasing, but much of the activity involved feeding; many species were presumably herbivores grazing the sparse algae that happen to grow up on the reef. I enjoyed the solitary greenish blue parrotfish which tended to be shy when I tried to approach with a camera. Most species stayed close to the reef though a few ventured higher into the water column. Some thin blue fish in contrast, stayed just beneath the water’s surface, and since one tends to look down while snorkeling, it was a while before I noticed them.

A reef fish sampler. Top row, from left: moorish idol, Zanclus cornatus with orange band surgeonfish, Acanthurus olivaceus; unknown white and gold-colored butterfly fish; yellow trumpetfish.  Bottom row, from left: fourspot butterflyfish, Chaetodon quadrimaculatus; whitebar surgeonfish, Acanthurus leucopareius; unidentified parrotfish.

Thin, well camoflauged bluish fish hanging out near the water's surface.

A shallow coral escarpment with a pair of ornate butterfly fish, Chaetodon ornatissimus.

References

Mahaney C, Witte A. 1993. Hawaiian Reef Fish. Blue Kirio Publishing.