Butterflyfish, with their tiny mouths, subsist mostly on tiny prey—coral polyps, small polychaete worms, amphipods, etc. But given the right opportunity, many (but not all) butterflyfish species will dine on all sorts of other things. Dead fish or larger invertebrates on the reef attract the attention of butterflies and many other fish. There’s often quite the crowd of opportunistic feeders gathered around the corpse, all so fixated on a chance for an easy meal that intruding photographers are largely ignored. We’ve seen a handful of these events at Mahukona recently.
Lined Butterflyfish are known to be difficult to approach and photograph. Attracted by the floating body of a half-eaten Hawaiian Whitespotted Toby* (below the butterflyfish on the left), these two allowed me to get quite close. Other species enjoying the free meal include the ubiquitous, highly opportunistic Saddle Wrasse, as well as Black Durgons, Pinktail Triggerfish, and a Yellow Tang.
These Fourspot Butterflyfish (you’ve got to count the spots on both sides of the fish) have found a broken-open sea urchin. Saddle Wrasses have joined in. Both this and the previous photo were taken at Mahukona.
We were snorkeling at Manase in Samoa in 2017 when we spotted a melee of fish swirling around a head of Acropora coral. We couldn’t identify what was attracting them—it was hidden deep in the coral—but it was apparently a dead something. Most of the crowd consisted of Sixbar Wrasses (a close relative of Hawaii’s Saddle Wrasse), Convict Tangs, and Orange-lined Triggerfish. While we were watching, this huge Longface Emperor and its companion showed up out of nowhere to see if they could get in on the bonanza. The emperors were apparently attracted by smell or by the frenzied activity of the smaller fish, or?
A closer look at the Longface Emperor. This thing was almost three feet long—big enough to startle us when it showed up. The species eats a wide variety of invertebrates and fish.
*Kind of strange to see a dead toby being fed upon by such a wide variety of fish. The bodies of these, like all puffers, contain a potent toxin to deter predation. Either these fish are immune or they know how to avoid the most toxic parts of the body, like the Japanese fugu chefs who prepare puffers for human consumption.