Scott Michael's Marine Musings

The hunting duo of the Celebes Maori wrasse (Oxycheilinus celebicus) and (Parupeneus cyclostomus) posing for the camera.

One thing that excites me about exploring coral reef communities are the amazing relationships that you can readily observe in this species-packed neighborhood. Anemones and anemonefishes. Pistol shrimps and shrimpgobies. Damsels and stony corals. The list goes on and on. But some of my favorite partnerships involve feeding relationships that exist between various reef fishes. The most common of these involves a substrate-disturbing species, like most goatfishes (family Mullidae), and an opportunist, like many of the wrasses (family Labridae). (This type of feeding association is referred to by trophic biologists as “following” [clever, huh?]: the fish that is followed is called the nuclear species while the fish doing the following is known as the attendant species). The goatfish stirs the sand or rubble with its chin barbels in an attempt to find something to eat. When it does this, it attracts the attention of neighbors, like the labrids, that see the goatfish’s foraging as an opportunity to jump on otherwise cloistered prey. The goatfishes will flush concealed crustaceans and small fishes, which the wrasses pounce on as they try to elude the mullid. It has been quantitatively demonstrated that wrasses that associate with goatfish enjoy greater hunting success than those that do not. It is so important to food acquisition, that a wrasse may defend its goatfish “gravy train” from other labrids that want to join in.

As they move from one locations to the next, the goatfish often swims just below and to one side of its labrid crony.

But the most interesting feeding association, which is one that apparently benefits both partners, exists between certain wrasses and the yellowsaddle goatfish (Parupeneus cyclostomus). These two buddies are truly attached at the fin! If you look at the photos above, you will see a Celebes Maori wrasse (Oxycheilinus celebicus) and a juvenile P. cyclostomus. This pair was skulking about on the edge of a shallow fringing reef in West Papua. I watched and photographed the pair for well over 30 minutes and most of the time the two fish stayed side-by-side. Occasionally, one or the other would move off a couple feet, but invariably, this odd couple would reunite. In one case, the goatfish became separated from the wrasse and upon discovering it’s solitude, it looked agitated and began to search for the Oxycheilinus. It swam up to several fish of the appropriate size until it finally found its wrasse pal. I watched as the goatfish probed crevices with its long barbels (this mullid uses these appendages to probe crevices not sand) as the wrasse vigilantly looked on. Both fish seemed to acquire some prey during these foraging bouts.

Release the hounds! The foraging friends attempt to ferret out hidden prey.

Ormond (1980) was the first to formally describe these types of relationships in a scientific publication. He observed that the bird wrasse (Gomphosus varius) and the yellowsaddle goatfish (he uses the older binomial, Parupeneus chryseredros) engage in this behavior in the Red Sea. He coined the term “interspecific joint-hunting” to describe it. This is a type of cooperative foraging behavior. The two fish swim together until they come to a coral colony or a rocky patch. Unlike foraging by following, the two fish begin working the area over together so that both species have the potential of benefiting. In some cases, one member of the hunting party goes “around a coral head one way, while the other goes round in the other direction.” Apparently the advantage is that the fossicking behavior of one fish may herd or scare prey into the path of its accomplice. More on this and other feeding associations in the future.

Reference:

Ormond, R. F. G. 1980. Aggressive mimicry and other interspecific feeding associations among Red Sea coral reef predators. Zool. Soc. Lond. 191:247-262.

Copyright (2008) Scott W. Michael