Photo of the Week: February 22, 2010

Hi Gang!

This week’s POTW is an image of a peacock grouper eating a just-captured yellow tang. The photograph was taken in Hawaii. The image is interesting, at least to me, for three reasons. One, like most underwater photographers I enjoy the challenge of capturing animal behavior. Predation is especially challenging because just being in the vicinity of the action can disrupt the activity. Two, peacock groupers (Cephalopholis argus) are not native to Hawaiian waters. In fact, the fishes commonly known as groupers that are so common in many reef communities around the world are nearly absent from Hawaiian waters. The peacock grouper was introduced to Hawaii from French Polynesia in the 1950’s in the hopes of creating a new fishery. If you have dived with Captain Steve or almost anyplace in Hawaii you are probably aware that peacock groupers have done remarkably well as populations are well established in many Hawaiian reef communities. Too well, in fact, according to many in the know. Peacock groupers are voracious feeders, and they consume huge numbers of reef fishes. So many, that spearfishing contests focusing strictly upon peacock groupers are being held in an attempt to reduce the numbers of peacock groupers in order to protect endemic species and the overall balance of life in Hawaiian reef communities.

Unfortunately, the hoped for fishery did not do very well because the locals lost interest in the fish as a food source after a number of people suffered from ciguatera (fish poisoning) that was traced to the consumption of peacock grouper. A study published in 2009 confirmed that ciguatera remains a potential problem with the species so it is probably wise for peacock grouper to remain on the reefs and off of our dinner plates.

Yellow tang (Zebrasoma flavescens, aka yellow sailfin tang and yellow surgeonfish) are omnipresent on Hawaiian reefs. They are one of the species that is commonly seen cleaning green sea turtles.

The third reason that this week’s POTW is special to me is because it serves to remind me of the way that peacock groupers and whitemouth moray eels (Gymnothorax meleagris) hunt together. It is a common on Hawaiian reefs to see one or more peacock groupers nuzzle up against a whitemouth moray or otherwise encourage the eel to leave its resting place so that the eel will begin to hunt, or at the very least, swim through the latticework of the reef and frighten potential prey for the groupers up into the water column. The peacock groupers follow the eel as it swims, and are quick to pounce on any disoriented fish or crustacean that gets spooked into the open.

Sometimes the groupers get a meal, and in other instances, their potential meal escapes by retreating into the hiding place in the reef. If injured or disoriented, the grouper’s intended prey can become an easy mark for an opportunistic whitemouth eel.

If you have never seen peacock groupers and whitemouth eels hunting in this fashion, ask Captain Steve to point it out to you the next time you are in Hawaii. He might not be able to find this activity on every dive, but if you give him a few tries my bet is that the Captain will be able to find a hunt in process.

When I captured this week’s POTW I was keeping my distance from the grouper and eel as I was watching them hunt. As the eel swam through the coral I saw a yellow tang dart out of the reef and rise a few inches up into the water column. In the blink of an eye, the yellow tang became a meal for the grouper. At that point I closed the gap so I could try to document the action with my camera. At first, the grouper didn’t move much as it fought to completely subdue the tang. But within a few seconds as the struggle continued a number of other fish gathered around in the hopes of picking up scraps or stealing part of the tang from the grouper. So, the grouper swam off with its meal, but before it did I was able to capture a few images, and that’s the story

I hope you enjoy this week’s POTW. See you next week!

Marty