Monthly Archives: September 2015

A young eagle ray

Eagle rays are frequent visitors to Mahukona.  We usually see adults, from four to six feet across, either singly, or more commonly in small groups.  For the last week or so a single juvenile, less than two feet across, has been lingering in the area.  I’ve read that eagle rays bear their live young in the fall, and that the young are about ten to twenty inches across at birth.  Based on this, I’d guess that this individual was born last fall.

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Young eagle ray in about fifteen feet of water at Mahukona. The catlike eyes are conspicuous.

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Feeling a rock with its mouth. Eagle rays have electrosensory organs in their mouths that help detect the buried mollusks and other invertebrates that constitute much of their diet.

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An adult eagle ray photographed at Mahukona in 2013.  As with many animal species—marine and otherwise—the eyes of adults are much smaller in relation to body size than in juveniles. (You may need to click on the photo to see the eyes here.)  The dark markings on the underside of the wings are absent on many individuals.  I think they are more common on older animals.

A lucky butterfly and an unlucky wrasse

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As I’ve mentioned previously, it’s fairly unusual for a snorkeler to see a fish attack and eat another fish, despite the abundance of both predator and prey species on the reefs.  I was surprised the other day at Mahukona to stumble upon a large cigar wrasse with a small multiband butterflyfish in its mouth. The wrasse, having a rather poor grip on the tail end of the butterfly, was trying to press its prey into the reef for a better purchase.  The butterfly was of course thrashing around attempting to free itself.  It was kind of hard to follow through the screen of my little point and shoot camera, but somehow the butterfly managed to get loose and flee into a cranny in the reef.  The wrasse tried in vain to follow.  The wrasse swam around excitedly for a couple of minutes, trying to relocate its now-vanished prey, completely oblivious of me, and then it moved on.  All this happened in about eight feet of water on the shallow reef that extends out from what the Mahukona regulars refer to as the first point.

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The butterflyfish struggles to free itself from the cigar wrasse’s rather tenuous grip.  Notice how the butterfly has flared the spines on its dorsal, ventral, and anal fins to discourage the wrasse from swallowing it.

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The wrasse wheels around trying to recapture the newly-escaped butterfly, which is fleeing into a hole.

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The wrasse gives up and swims away.

The wrasse was likely the same female I’d seen in the same location in June, but, I think, not the same as I’d seen nearby in March. As I’d mentioned in a March post, I think this is an uncommon color variant, at least in Hawaii.

In addition to the event shown here, Marla and her sister Wendy have observed these fish preying on fish on two other occasions.

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This is probably the same cigar wrasse, photographed in June.

Samoan oddities

Some of the stranger fish we saw in Samoa:

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The handsome, bold, banded goby, Americans Samoa, 4 ft. Gobies are the largest family of marine fish and are well-represented in both Hawaii and Samoa, but Samoa has about three times as many species as Hawaii. All the Hawaiian species lie on the bottom or other substrate, while several Samoan species swim off the bottom like this one.

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Latticed sandperch, north coast of Savaii, 30 ft. I really liked this goofy looking guy. Another case of odd-shaped pupils. Hawaii has a closely related sandperch.

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I cannot identify this relatively plain looking damselfish that I spotted in very shallow water in American Samoa. I’m sure it’s not a new species or anything, but it appears to be missing from the encyclopedic fish ID book I referred to in the last post. I’m going to post this photo on some fish geek forums and hope someone knows what it is. [Update: It’s a juvenile twospot damselfish.  This fish is in fact described in Allen et al., but the photo in that book is of an adult, which looks quite different from the juvenile.  Thanks, Janet!)

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A group of pearly dartfish heading for shelter. North coast of Savaii, 30 ft.

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Again, not that odd, I guess, but I liked watching them disappear into their hole. Hawaii has a closely related dartfish, but I’ve never seen it.

A few Samoan beauties

Marla and I just returned from another of our semi-annual trips to Samoa.  In addition to our usual week working in American Samoa we spent a week vacationing in independent (formerly Western) Samoa.  We took a two-tank scuba dive from Dive Savaii located on the north coast of Savaii.  This trip I took along a better camera than my usual underwater point and shoot.  Unfortunately the camera battery (cheap third party variety—I’m such an idiot) gave out less than half way through the first dive.  Managed a few nice shots anyway.

As I’ve alluded to previously, Samoa, being far less isolated than Hawaii, has more than eight hundred native reef fish species as opposed to fewer than four hundred in Hawaii.  While Hawaii has its share of dazzlingly beautiful species, Samoa has many more, and many that are very different from anything encountered in Hawaii.  Here are a few.

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Blue-green damselfish, one of the signature fish of South Pacific reefs. While damselfish are well represented in Hawaii, none of the South Pacific’s many vivid blue and blue-green species are present there.

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South-seas devil, another very common South Pacific damselfish. The reefs here have a confusing number of similar, iridescent blue damselfish. This species is distinguished by the tiny white dots on its side and by the pale blue patch behind the dorsal fin*.

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Speckled damselfish. Doesn’t seem like a great name for these striped fish. This bold little guy is only about an inch long.

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Another shot, this time showing the eye spot at the rear of the dorsal fin. Many species small reef fish have a similar spot, apparently to confuse potential predators as to which end of the fish is the front.

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The psychedelic looking yellow-edged lyretail, a type of grouper. Hawaii has no native shallow water groupers.

 

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Male redfin anthias, a grouper relative.  This is among the most beautiful reef fish I’ve ever seen. This photo does reasonable  justice to the incredibly subtle coloration. Hawaii actually has some similarly gorgeous native anthias. This and the lyretail above were photographed using scuba at about thirty feet down. The rest were shot while snorkeling.

*I used Allen, Steen, Humann and DeLoach’s Reef Fish Identification: Tropical Pacific to identify the fish we saw in Samoa.  This book is a fish geek’s dream, with 2,500 photos of over 2,000 species.