View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Aquila Digital Community 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- Published by The Aquila Digital Community, 1998 1 Gulf of Mexico Science, Vol. 16 [1998], No. 2, Art. 12 [J) ::r: 0 ~ t>1~ B; ~ z 0 ~ t>1 [J) Fig. 1. Aluterus scriptus nocturnally moored on crossmember of offshore production platform. Photograph by Jeff Childs. Nl Nl <.0 https://aquila.usm.edu/goms/vol16/iss2/12 2 DOI: 10.18785/goms.1602.12 Childs: Nocturnal Mooring and Parking Behavior of Three Monacanthids (Fil 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.