Photo of the Week: March 19, 2012

Hi Gang!

This week’s POTW is a picture from one of my dives in Hawaii. It is a shot of a gathering of brilliant yellow milletseed butterflyfish, Chaetodon miliaris, eating fertilized eggs out of the purple hued nest of a Panamic sergeant major, Abudefduf troschelli. The milletseed butterflyfish is also commonly referred to as the lemon butterflyfish and the millet butterflyfish.

I have read that those that focus on the vivid yellow hue tend to call the fish a lemon butterflyfish, while the taxonomist that gave the species its species name, miliaris, likely paid more attention to the numerous vertical rows of black spots on the body. The spots are believed to have reminded him of milletseeds.

The milletseed butterflyfish is endemic to Hawaii, and the species is generally believed to be the most numerous of all of the 24 species of butterflyfishes that occur in Hawaiian waters. The milletseed butterflyfish is usually encountered over relatively shallow areas of reef flats and on seamounts.

As an adult, the milletseed butterflyfish reaches a maximum length of just over five inches. Unlike many species of butterflyfishes that tend to live in a male/female pair as adults, milletseed butterflyfish tend to gather in aggregating groups except during their breeding season when they, too, pair off. When feeding, milletseed butterflyfish tend to move over a reef in a shoal as they search for food.

In the case of the eggs in the nest cultivated by a male Panamic sergeant major, the number of milletseed butterflyfish usually proves to be too many for the sergeant major, a damselfish, to fend off. Overwhelmed, he will almost always swim away while the butterflyfish enjoy their feast. Milletseed butterflyfish also prey on zooplankton. They also serve as cleaners for some other species of reef fishes.

In areas where milletseed butterflyfish are commonly seen it is not uncommon to find an actively feeding shoal raiding the nest of a Panamic sergeant major. Knowing that I had a good chance to find an active shoal, I set up my camera system with a Nikon 17-to-55 mm zoom lens so that I could vary my composition depending on how close I could get to the shoal without disrupting the behavior. Getting close did not prove to be a problem as very little was going to stop these fish from gorging themselves on the eggs.

I hope you enjoy this week’s POTW!

See you next week,

Marty