Gulf of Mexico Science Volume 16 Article 12 Number 2 Number 2

1998 Nocturnal Mooring and Parking Behavior of Three Monacanthids (Filefishes) at an Offshore Production Platform in the Northwestern Gulf of Mexico Jeff hiC lds Texas A&M University, Corpus Christi

DOI: 10.18785/goms.1602.12 Follow this and additional works at: https://aquila.usm.edu/goms

Recommended Citation Childs, J. 1998. Nocturnal Mooring and Parking Behavior of Three Monacanthids (Filefishes) at an Offshore Production Platform in the Northwestern Gulf of Mexico. Gulf of Mexico Science 16 (2). Retrieved from https://aquila.usm.edu/goms/vol16/iss2/12

This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf of Mexico Science by an authorized editor of The Aquila Digital Community. For more information, please contact [email protected]. Childs: Nocturnal Mooring and Parking Behavior of Three Monacanthids (Fil

228 GULF OF MEXICO SCIENCE, 1998, VOL. 16(2)

vice, Gulf of Mexico OCS Region, Leasing and ed 198 km south of Sabine Pass on the Texas­ Environment Section (MS 5432), 1201 Elmwood Louisiana border, encompasses an area of 67 Park Boulevard, New Orleans, Louisiana 70123. km2 and is pear shaped. A coral reef cap reach­ es to within 20 m of the surface, with surround­ ing water depths of between 100 and 120 m. Together with the West Flower Garden Bank, located 12 km to the west, these banks support the northernmost tropical coral reef commu­ Gulf of Aiexico Science, 1998(2), pp. 228-232 nities on the North American continental shelf © 1998 by the Marine Environmental Sciences Consortium of Alabama (Rezak et al., 1985). The Flower Garden Banks were designated a National Marine Sanctuary NOCTURNAL MOORING AND PARKING BE­ in Jan. 1992 (National Oceanic and Atmo­ HAVIOR OF THREE MONACANTHIDS spheric Administration, 1991), and a third (FILEFISHES) AT AN OFFSHORE PRODUC­ bank, Stetson Bank (located 55 km northwest TION PLATFORM IN THE NORTHWEST­ of the West Flower Garden Bank), was added ERN GULF OF MEXICO.-This biological in Oct. 1996. note documents a unique nocturnal behavior In May 1994, while conducting night dives at demonstrated by three species of monacan­ the Mobil platform, a solitary A. scriptus, esti­ thids (filefishes) on an offshore production mated at 92 em in total length, was observed platform in the northwestern Gulf of Mexico. grasping a piece of sponge ( Callyspongia vagi n­ It also contrasts the observed lack of such be­ aZis) in its mouth. The "mooring" sponge was havior among monacanthids on natural reefs attached at 24-m depth on the down-current in the region. side of a platform leg. Thus, the fish was effec­ Mobil's High Island A389-A platform stands tively moored to the platform structure and 1.5 km east of the East Flower Garden Bank was afforded an opportunity to rest in an area (27°54'26"N, 093°34'43"W). The platform was where currents were reduced. The fish main­ installed in Oct. 1981 and began production in tained its position easily while grasping the Sept. 1988. The platform rests in 125 m water sponge, only releasing its grasp after I dis­ and reaches a height of 23 m above sea level. turbed it by approaching it closely or by aiming Underwater, the platform structure functions the dive light I was using. The fish moved less as an artificial reef, supporting fauna and flora than 1 m from the sponge before I turned off characterized as originating from the Carib­ my light and withdrew. Later in the dive I re­ bean (Dokken et al., 1995; Rooker et al., turned to the location and observed the fish 1997). Three distinct depth zones are identi­ moored to the same sponge. Mooring behavior fied related to the biofouling community on is defined here as that behavior during which the structure (Adams, 1995; Dokken et al., a fish orally affixes to an attached structure in 1995). Sponges, molluscs, algae, and hydroids order to maintain its position. dominate the biofouling community (Adams, Subsequent night dives at the platform in 1995; Dokken et al., 1995), whereas coral col­ ensuing years have yielded similar opportunis­ onies are few and small. Rooker et al. (1997) tic observations of A. scriptus moored to the characterize the fish assemblage associated Mobil platform (Fig. 1). Observers detected 11 with the platform, reporting carangids and of 12 individuals displaying similar behavior as scombrids as the dominant ichthyofauna. Reef­ they were moored to sites on the down-current associated fishes comprise mainly labrids, po­ side of the platform structure during one macentrids, and serranids (Rooker et al., week-long excursion on the platform (Stanton 1997) . Fish surveys conducted on self-con­ et al., 1998). Night dives conducted during tained underwater breathing apparatus (SCU­ other excursions resulted in nocturnal obser­ BA) from 1991 through 1996 regularly chron­ vations of A. scriptus moored to sessile organ­ icled three species of monacanthids at the plat­ isms attached to the platform structure. How­ form (Childs, unpubl. data); they were ever, the frequency of these observations was scrawled filefish (Aluterus scriptus), orangespot­ not documented, except periodically on vid­ ted filefish ( Cantherhines pullus), and white­ eotapes while divers were filming the behavior. spotted filefish (C. macrocerus). Surveys were Most A. scriptus observed at night were either typically conducted to 60 m in depth, with moored or maintained a position close to the some as deep as 80 m. Night dives were rarely platform structure by balistiform locomotion. conducted below 31 min depth and never be­ It is likely that some A. saiptus were disturbed low 40 m. when divers closely approached prior to the The nearby East Flower Garden Bank, locat- diver's awareness of the fish; these fish proba-

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Fig. 1. Aluterus scriptus nocturnally moored on crossmember of offshore production platform. Photograph by Jeff Childs.

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230 GULF OF MEXICO SCIENCE, 1998, VOL. 16(2)

bly released from their moorings. Mooring be­ er individual A. scriptus select mooring sites on havior appears to be characteristic of A. scriptus horizontal crossmembers over those on plat­ on the offshore platform. form legs was not evident from my observa­ While searching for additional A. scriptus tions. mooring sites on the platform, both C. macro-­ Cantherhines macrocents was also observed cents and C. pullus exhibited similar yet slightly maintaining position in the water adjacent to modified behavior. These species were ob­ either horizontal or vertical supports using bal­ served mooring to the platform, although the istiform locomotion. However, C. rnacrocerus moorings they were orally affixed to were not and C. pullus were found to moor and park necessarily demospongid sponges. Tunicates, only at crossmember joints. It remains to be cirripedians, and even rope or fishing line determined whether such protected nocturnal were used as moorings by individual fish. Also, resting sites provide an ecological advantage these species were never observed moored in for individual C. macrocerus or C. pullus. the open, as was A. scriptus, but were rather Mooring behavior was only observed on the found in crevices created by sessile inverte­ down-current side of the structure. Current di­ brates (poriferans, ascidiaceans, cirripedians, rection and velocity varied dynamically at the and cnidarians) occupying joints on the plat­ platform and were largely unpredictable and form structure. Such sites provided the fishes unstable. Currents at the platform often varied with considerable protection from currents, in depth, as they did from one end of the large nocturnal predators, and were effective structure to the other. For example, currents nocturnal resting sites. adjacent to the north end of the platform were Behavior in which fishes are resting on a sub­ often moving in significantly different direc­ strate is here considered "parking behavior." tions than were those at the south end adjacent Whereas A. scriptus exhibits nocturnal mooring to the structure. Horizontal current flow ap­ behavior, C. macrocerus and C. pullus demon­ peared more stable the farther away one strate nocturnal mooring and parking behav­ moved from the structure. Current velocities ior. varied from 0 to at least an estimated 7.2 km/ Monacanthids exhibiting nocturnal mooring hr. Thus, mooring behavior is likely to afford and/ or parking behavior at the platform were dorsoventrally compressed fish like A. scriptus all observed between 10 and 30 m in depth. with the ability to rest in protected areas with­ Nocturnally parked filefishes were absent in out expending considerable energy to main­ water shallower than 10 m at the platform, pos­ tain position. sibly because of a lack of structural joints be­ Nocturnal resting for reef-associated fishes is tween 0 and 10 m in water depth. However, well known, yet specifics such as sleeping site this does not adequately explain the absence selection are poorly documented. Several spe­ of A. scriptus within this depth range. It is more cies of scarids (Winn, 1955; Winn and Bar­ plausible that this region of the platform is dach, 1959, 1960) and labrids (Hobson, 1965) strongly affected by surface wave and surge dy­ are known to produce mucous envelopes while namics, thereby exposing nocturnally parked resting in protected areas, which is thought to fishes to disturbing and undesirable natural reduce predation by nocturnal predators. Hob­ forces that inhibit rest. son (1965) documents some sleeping sites se­ The maximum depth at which nocturnal lected by coastal fishes observed off Baja Cali­ parking or mooring occurs was not deter­ fornia, Mexico. He describes general diurnal­ mined. Fish surveys conducted during daylight nocturnal resting sites for several species with­ hours reveal all three monacanthid species oc­ in the following observed groups: serranids, curred to depths of at least 62 m. Night dives pomacentrids, labrids, scarids, chaetodontids, were not typically conducted below 31 m, and acanthurids, blenniids, balistids, holocentrids, when they were, A. scriptus was not observed lu~anids, apogonids, pomadasyids, carangids, below 30 m. Therefore, it is unknown whether and sciaenids. Unless disturbed, most diurnal A. scriptus occurs at deeper depths on the plat­ reef fishes are relatively dormant on clark form at night. nights but may remain active at night, given Some A. scriptus were found moored on plat­ adequate moonlight (Hobson, 1965). A study form legs that were vertically oriented; howev­ of fish fauna associated with two offshore plat­ er, horizontal crossmembers were also used as forms showed reef-associated icthyofauna rest­ mooring sites. Crossmembers occur at 10, 23, ing near pilings, in protected areas below and 37 m as part of the top 40 m of the un­ cross-members, or between pilings and nearby derwater structure. Crossmembers are found objects (Hastings et al., 1976). Whereas C. pul­ deeper and may be used by A. scriptus. Wheth- lus was identified at one of these platforms,

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Hastings et al., (1976) did not report noctur­ like that of many monacanthids, may experi­ nal parking behavior for C. pullus or other spe­ ence difficulty in finding suitable resting sites cies observed during the study. in which to settle. Nocturnal mooring and Reef-associated fishes select sleeping sites parking behavior is a unique solution to the that offer shelter of sorts. Sites described by apparent lack of resting sites on offshore plat­ Hobson (1965) typically consist of crevices or forms. areas affording either partial or complete shel­ ter. Some fishes rest among rocks or depres­ Acknowledgments.-! extend my gratitude to sions in loose substrate, such as sand (Hobson, Carl Beaver, Susan Childs, Quenton Dokken, 1965; Hastings et al., 1976). Dubin and Baker Hector Guiterrez, Emma Hickerson, David (1982) found princess parrotfish (Scarus tae­ Mayer, John Reeves, and Gregg Stanton for niopterus) selecting nocturnal refuge near reef their assistance and support. slopes or in dense coral colonies. Their study revealed two cover-seeking behaviors that dem­ onstrate a preference of resting sites. Robert­ LITERATURE CITED son and Sheldon (1979) investigated competi­ ADAMS, C. L. 1995. Species composition, abundance tion for sleeping sites among the bluehead and depth zonation of sponges (Phylum Porifera) wrasse ( Thalassoma bifasciatum) and damselfish­ on an outer continental shelf gas production plat­ es (Eupomacentrus dorsopunicans and E. plani­ form, northwestern Gulf of Mexico. MS thesis, fmns). They concluded that damselfish defend Center for Coastal Studies, Texas A&M Univ.-Cor­ food and egg masses from wrasse but not the pus Christi, Corpus Christi, TX. sleeping sites that were superabundant in the DOKKEN, Q. R., C. BEAVER, S. Cox, C. ADAMS,]. RooK­ study area. ER, AND]. CHILDS. 1996. Characterization of bio­ Monacanthids reported in this note are fouling communities on oil and gas production platforms: impact on finfish assemblage, p. 142- commonly observed at the Flower Garden 153. In Proceedings, fifteenth annual Gulf of Mex­ Banks and Stetson Bank (Childs, unpubl. ico Information Transfer Meeting, December data). Filefish resting sites were investigated 1995. OCS report MMS 96-0056. U.S. Department while conducting night dives at each of these of the Interior, Minerals Management Service, locations, with the intention of observing sim­ Gulf of Mexico OCS Regional Office, New Or­ ilar parking behavior. Filefish were rarely ob­ leans. served at night on these natural reefs; one C. DUBIN, R. E., AND J. D. BAilliR. 1982. Two types of macmcerus was found sheltered in a crevice be­ cover-seeking behavior at sunset by the princess tween a coral colony and a sponge at the East parrotfish, Scarus taeniopterus, at Barbados, West Flower Garden Bank. At Stetson Bank, a soli­ Indies. Bull. Mar. Sci. 32:572-583. HASTINGS, R. W., L. H. OGREN, AND M. T. MABRY. tary was observed maintaining po­ A. scriptus 1976. Observations of the fish fauna associated sition immediately down-current of a hard with offshore platforms in the northeastern Gulf clay-siltstone outcropping. The fish was par­ of Mexico. Fish. Bull. 74:387-402. allel with the rock face and was not moored, HOBSON, E. S. 1965. Diurnal-nocturnal activity of as is characteristic of filefish occurring at the some inshore fishes in the Gulf of California. Cop­ offshore platform. The individual was likely eia 1965:291-302. benefiting from the shelter produced by the NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRA­ rock instead of expending more energy by ex­ TION. 1991. Final environmental impact statement posing itself to the current and the potential and management plan for the proposed Flower Garden Banks National Marine Sanctuary. U.S. risk of predation. Department of Commerce, National Oceanic and Complex coral colonies at the Flower Gar­ Atmospheric Administration, Sanctuaries and Re­ den Banks afford an abundance of nocturnal serves Division, Washington, DC. resting sites, where filefishes may moor or REZA!(, R., T. J. BRIGHT, AND D. W. McGRAIL. 1985. park; however, the network of coral colonies Reefs and banks of the northwestern Gulf of Mex­ constrains observations of individuals likely ico; their geological, biological, and physical dy­ sheltered within. Filefish are likely to employ namics. John Wiley and Sons, New York. parking behavior to facilitate nocturnal rest­ ROBERTSON, D. R., AND J. M. SHELDON. 1979. Com­ ing on offshore platforms where sleeping sites petitive interactions and the availability of sleeping are limited, particularly for larger reef fish, sites for a diurnal coral reef fish.]. Exp. Mar. Bioi. Ecol. 40:285-298. such as A. scriptus. Mooring or parking down­ ROOKER, J. R., Q. R. DOKKEN, C. V. PATTENGILL, AND current of the platform structure offers pro­ G. ]. HoLT. 1997. Fish assemblages on artificial tection and stability that are otherwise not and natural reefs in the Flower Garden Banks Na­ available to larger fish. Furthermore, fishes tional Marine Sanctuary, USA. Coral Reefs 16:83- with a dorsoventrally compressed body type, 92. https://aquila.usm.edu/goms/vol16/iss2/12 4 DOI: 10.18785/goms.1602.12 Childs: Nocturnal Mooring and Parking Behavior of Three Monacanthids (Fil 232 GULF OF MEXICO SCIENCE, 1998, VOL. 16(2)

STANTON, G. R., D. P. MAYER, AND J. CHILDS. 1998. ---, AND J. E. BARDACH. 1959. Differential food The behavior of scrawled filefish (Aluterus scriptus) selection by moray eels and a possible role of the (Osbeck 1765) on an offshore production plat­ mucous envelope of parrotfishes in reduction of form in the Gulf of Mexico, p. 72-82. In: Diving predation. Ecology 40:296-298. for Science, eighteenth annual Scientific Diving ---, AND ---. 1960. Some aspects of the com­ Symposium. B. Hartwick, E. Banister and G. Mor­ parative biology of parrotfishes at Bermuda. Zool­ ariu (eds.). American Academy of Underwater Sci­ ogica 45:29-34. ences, Nahant, MA. WINN, H. E. 1955. Formation of a mucous enve­ JEFF CHILDS, Center for Coastal Studies, Texas lope at night by parrot fishes. Zoologica 40:145- A&M University-Cmpus Christi, Corpus Christi, 147. Texas, 78412.

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