166 . IlULLETINOFMARINESCIENCE.VOL.33. NO.I. 1983 Channel). Harpiliopsis beaupresii (Audouin, 1852)-(Mauritius). Harpi/iopsis depressa (Stimpson, 1866)-(Zanzibar). Harpiliopsis spinigera (Ortmann, 1870)-(Farquhar Is., Seychelle Islands).· Ha- modactyloides incompletus (Holthuis, 1958)-(Zanzibar).· LITERATURE CITED Bruce, A. J. 1978. A report on a collection of pontoniine shrimps from Madagascar and adjacent waters. Zool. Joum. Linn. Soc. 62: 205-290, figs. 1-44. --. 1979. Onycocarisfurculata sp. nov., a new pontoniine shrimp from La Reunion. Cahiers Indo-Pacifique 1: 323-334, figs. 1-4. --. 1980. Notes on some Indo-Pacific Pontoniinae. XXXII. The occurrence of Paratyptol1 siebenrocki Balss on La Reunion. Crustaceanana 38: 237-246, figs. 1-4. Ribes, S. 1978. La macrofaune vagile associee ii la partie vivante des scleractinaires sur un recif frangeant de I'Be de la Reunion (Ocean Indien). These de doctorat de 3 erne cycle en oceanologie, Universite Aix-Marseille 2. DATEACCEPTED: October 21, 1982. ADDRESS: Division of Natural Sciences, The Northern Territory Museum. P.O. Box 4646. Darwin, Australia. 5794. IH'LI.ETINOFMARINESCIENCE.33(1): 166-171. 1983 FORAGING BEHAVIOR OF THE WEST ATLANTIC TRUMPETFISH, AULOSTOMUS MACULA TUS: USE OF LARGE, HERBIVOROUS REEF FISHES AS CAMOUFLAGE Richard B. Aronson A limit to the density of Batesian mimics of an unpalatable species has been postulated, due to predator learning (Carpenter, 1936; Rothschild, 1971). Simi- larly, one might expect a limit to the frequency with which a predator camouflages itself in a particular manner in order to capture visually-oriented prey. The west Atlantic trumpetfish, Aulostomus maculatus Valenciennes, 1842 (Aulostomidae) is a coral reef species that feeds primarily on fishes (Randall, 1967), exhibiting several modes of foraging that employ camouflage. The evolutionary problem of prey recognition may have selected for a limit to the frequencies with which A. maculatus utilize their various forms of camouflage. Here I discuss one type of camouflage: A. maculatus associate with large, herbivorous fishes, apparently to disguise themselves. A detailed examination of the associations was undertaken to determine whether they are, in fact, modes of foraging. The prediction of a limit to the use of particular modes of predator camouflage was tested by observing the frequencies of those modes. Aulostomus maculatus commonly hunt by ambush. They suspend their elongate bodies, head down, over the bottom and dart down to attack prey (Randall, 1968). They are known to align with gorgonians, long sponges and elongate artificial objects (e.g. ropes). Such behavior apparently conceals trumpetfish from their intended prey (Eibl-Eibesfeldt, 1955; Randall, 1968; Scaff, 1980). Randall (1968) describes A. maculatus as usually "brown or reddish brown, with lengthwise pale lines, scattered small black spots, and a black streak on the upper jaw .... " They are, however, able to change color. Randall (1968) reports color phases in which the upper half of the head is yellow or purple. Color change NOTES 167 may aid A. maculatus in foraging by providing camouflage. For example, indi- viduals that follow, and hunt in, schools of blue chromis, Chromis cyanea, often adopt bright blue snouts (Kaufman, 1976). In another form of camouflage (the subject of this paper), A. maculatus align with, or swim in schools of, other fishes of approximately the same length. Trum- petfish have been described as aligning with parrotfishes (Scaridae; Eibl-Eibesfeldt, 1955; Scarr, 1980), groupers (Serranidae; Eibl-Eibesfeldt, 1955; Collette and Tal- bot, 1972; Scarr, 1980) and the Spanish hogfish, Bodianus rufus (Collette and Talbot, 1972). When aligning with another fish, " ... the trumpetfish's body arches in line with the other fish's spine" (Scarr, 1980). Collette and Talbot (1972) noted that an A. maculatus aligning with a graysby, Epinephelus cruentatus, was brown, like the grouper. A yellow phase individual was observed aligning with a red and yellow B. rufus (Collette and Talbot, 1972). Kaufman (1976) found many blue-snouted A. maculatus swimming in groups of blue tang, Acanthurus coeru- leus. Eibl-Eibesfeldt (1955) observed A. maculatus attacking prey from their po- sitions of alignment with parrotfishes, and felt certain that the purpose of such alignment was camouflage. Hobson (1968) noted that Pacific cornetfish, Fistularia petimba, also use parrot fishes and groupers as camouflage to approach prey. METHODS AND STUDY AREA Field observations were made during 19-26 January 1981 while snorkeling in and around a shallow (-1.5 to -3.0 m) reefa few meters off the west (leeward) coast of Bonaire, Netherlands Antilles. The reef is at Plaj'i Lechi, just north of the town of Kralendijk, at approximately 12°10' IO"N latitude and 68°17' IO"W longitude. It consists primarily of the branching corals Acropora cervicornis and A. pal- ma/a. and vertical sheets of the hydrocoral Millepora complana/a. Aulos/omus macula/us were com- monly seen around this reef. Formal observations (behavioral sequences and reef surveys) were made between 0830 and 1100 h. Incidental observations were made at all hours of the day. Eighteen behavioral sequences of A. macula/us were recorded over a period of 5 d. After standard length (SL) was estimated and color noted, each individual was watched until lost from view, or for a maximum of 5 min. All changes in behavior, color and orientation (horizontal vs. vertical) were recorded. Prey items and intended prey items were identified when possible. On two mornings (19 and 20 January), visual surveys were conducted to determine the proportions of A. macula/us engaged in various modes offoraging. These surveys were made by swimming around the reef and noting the activity of each A. maculatus at the moment of first sighting. RESULTS Three Aulostomus maculatus were observed aligning with parrot fishes during the recording of behavioral sequences, two during the reef surveys and seven during incidental observation. Six individuals aligned with terminal phase queen parrotfish, Scarus vetula, two with initial phase Scarus vetula, and four with initial phase stoplight parrotfish, Sparisoma viride. The interactions were much as de- scribed by Eibl-Eibesfeldt (1955) and Scarr (1980), with the A. maculatus generally conforming very closely to the dorsal profiles of the parrotfishes. The colors of the trumpetfish conformed, in most cases, to those of the parrotfishes (Ta- ble 1). On two occasions A. maculatus were observed associating with terminal phase Scarus vetula for > I min. These A. maculatus foraged when the Scarus vetula stopped to feed on algae; the trumpetfish examined small cavities in the reef, and, one, made strikes at several Eupomacentrus partitus. The other encounters were considerably shorter (.::5 30 s). In these instances, the trumpetfish aligned briefly and then swam off. One individual made an unsuccessful strike at an unidentified goby from its position of alignment with an initial phase Sparisoma viride. In another case, a terminal phase S. vetula chased the aligning A. maculatus and 168 BUllETIN OF MARINE SCIENCE. VOL 33. NO. I. 1983 Table I. Summary of color patterns of A ulostomus maculatus aligning with parrotfishes and swim- ming in schools of Acanthurus spp. Colors reported for Aulostomus maculatus are thosc recorded at moment of first observation (g-s, gray with longitudinal, silver stripes; greens and blues are irridescent shades for A. maculatus) Number Herbivore(s) Aulostomus maculalus Color Observed Terminal phase Scarus vetula g-s venter, light green dorsum and snout 2 (blue, pink and green pastel gray body, blue snout 2 shades) g-s venter, light green dorsum, blue snout I g-s body, light green snout I Initial phase S. vetula g-s body and snout 2 (black, white and gray) Initial phase Sparisoma viride g-s body and snout 2 (red and gray) brown and silver lateral stripes, gray snout I gray body, blue snout I School of Acanthurus spp. gray body, blue snout 7 (gray and irridescent blue) dark gray body, blue snout 2 g-s body and snout 2 g-s body, blue snout I gray body and snout I g-s body, light green snout I nipped it. An initial phase Sparisoma viride did the same, and another initial phase S. viride chased away an A. maculatus with a flick of its tail. In at least two observed cases, trumpetfish were in direct contact with parrotfishes, and appeared to be riding their dorsa and/or leaning on their extended pectoral fins. A group consisting of 30 to 50 ocean surgeons, Acanthurus bahianus. 10 to 15 doctorfish, A. chirurgus, and/or blue tang, A. coeruleus, and two to five goatfish, Mulloidichthys martinicus and Pseudupeneus maculatus, was seen on the reef on numerous occasions; this appeared to be the same school in all cases. The school was seen 11 times during formal and incidental observations. It contained no Aulostomus maculatus on four occasions. Twice the school had one trumpetfish, three times it contained two individuals, and twice there were three A. maculatus present. The herbivores moved through the reef, invading damselfish (Pomacen- tridae) territories and cropping their algal lawns (see Ogden and Lobel, 1978 for review). The trumpetfish searched while the herbivores fed; when the herbivore moved on, the A. maculatus rejoined the group. Two trumpetfish made strikes at unidentified objects while they were swimming with the school. Aulostomus maculatus which swam with the school generally had bodies that were solid gray or gray with longitudinal, silver stripes, and most had irridescent blue snouts (Table 1). The gray coloration matched the bodies of Acanthurus bahianus and A. chirurgus, and the blue snouts conformed to the irridescent margins of the dorsal and anal fins of A. bahianus. as well as to the overall body coloration of A. coeruleus. Support for the idea of camouflage comes from a behavioral sequence in which two Aulostomus maculatus actually changed color to match changes in the fishes with which they were swimming. The two trum- petfish were light gray (like the Acanthurus spp.) with blue snouts.