Northeast Gulf Science Volume 11 Article 7 Number 1 Number 1

7-1990 Aspects of the Ecology of the Moon Jellyfish, Aurelia aurita, in the Northern Gulf of Mexico Carol L. Roden National Marine Fisheries Service

Ren R. Lohoefener National Marine Fisheries Service

Carolyn M. Rogers National Marine Fisheries Service

Keith D. Mullin National Marine Fisheries Service

B. Wayne Hoggard National Marine Fisheries Service

DOI: 10.18785/negs.1101.07 Follow this and additional works at: https://aquila.usm.edu/goms

Recommended Citation Roden, C. L., R. R. Lohoefener, C. M. Rogers, K. D. Mullin and B. Hoggard. 1990. Aspects of the Ecology of the Moon Jellyfish, Aurelia aurita, in the Northern Gulf of Mexico. Northeast Gulf Science 11 (1). Retrieved from https://aquila.usm.edu/goms/vol11/iss1/7

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ASPECTS OF THE ECOLOGY OF THE survey days were accomplished in each MOON JELLYFISH, Aurelia aurita, area per season. IN THE NORTHERN GULF OF MEXICO Transect directions were either north­ south or east-west, generally perpen­ In the spring and fall of 1987, aerial dicular to the mainland. Offshore tran­ surveys were used to study the distribu­ sects extended from the mainland or tion and abundance of surfaced and barrier islands 15 to 20 minutes of lati­ near-surface schools of red drum tude or longitude seaward (28 to 37 km). (Sciaenops ace/latus) and other marine Inshore transects were flown over the ( animals. One species commonly observed waters of bays and .sounds up to 10 NM in large aggregations was the moon jelly­ (19 km) inland. Each study day, a random fish, Aurelia aurita. When near the sur­ starting point and random direction of face and aggregated, the cream to pink work were chosen. Approximately 10 to globular animals were obvious. 12 transects, 4 minutes of latitude or Little is known about the abundance longitude apart, were flown per day. We and distribution of Aurelia in the Gulf of used a single-engine, overhead wing air­ Mexico. Various trawl studies have craft with retractable landing gear (Cessna reported sporadic moon jellyfish cap­ 172-RG type) as a study platform. Two tures (National Marine Fisheries Service trained and experienced observers, one Resource Surveys cruises, pers. obs.). on each si.de of the aircraft, surveyed The short lifespan of the adult medusae through open window.s. Surveys were con­ (Loosanoff 1962) makes abundance and ducted only when seas were no greater distribution studies difficult. Our aerial than 3 feet and whitecaps covered less surveys provided a unique opportunity to than 50% of the sea surface (Beaufort study the abundance and distribution of scale 3). The aircraft's airspeed was near-surface aggregations of moon approximately 167 kmlh. Daily survey jellyfish. duration was usually 4 to 4.5 hours, and usually flown between 1000 and 1500 h. STUDY METHODS A 55 degree angle of observation was defined by placing tape reference marks The coastal Gulf of Mexico, from the on window frames and wing struts. Be­ Rio Grande River, Tex. to Key West, Fla., cause of the fuselage, the angle between was divided into 7 study areas. Military 0 and 21 degrees could not be observed. airspace restrictions precluded surveys Thus, sightings were made in a 34 degree between Perdido Bay, Ala. and Cape San effective strip (between 21 degrees and Bias, Fla. Logistics precluded study of 55 degrees) on both sides of the airplane. the area between Lake Calcasieu and White Lake, La. Survey altitude alternated between 305 m (1000 ft), with a survey strip width of Spring surveys (April through July) 637 m, and 475 m (1500 ft), with a survey and fall surveys (September through strip width of 954 m. December) were conducted in each of the 7 study areas with 2 exceptions. The DATA ACQUISITION AND ANALYSIS Central Florida study area was studied only in the fall and the Louisiana study Data were recorded using a portable area was surveyed twice in the spring. A computer interfaced with a Loran-e navi­ 21 day period per study area was allotted gation device. The aircraft's position to each spring and fall survey. Weather (latitude and longitude) was automatic­ was the major limiting factor and 6 to 11 ally recorded every 30 seconds, along

Published by The Aquila Digital Community, 1990 1 Gulf of Mexico Science, Vol. 11 [1990], No. 1, Art. 7 64 Short papers and notes with time, heading, and ground speed. strip were so numerous that counting Observers recorded, and updated as them was difficult. Aggregations ranged necessary, altitude and environmental in size from scattered small "spots" to conditions including weather, sea state, areas where the observer's entire field of water turbidity, sunlight penetration, view was surfaced moon jellyfish. Aggre­ glare, and water color. gations were generally tightly packed A ratio estimator was used to esti­ and shape varied from circular to an mate the density of moon jellyfish aggre­ elongated oval. gations per 100 square NM (Jolly 1969, Caughley 1977). DISCUSSION AND CONCLUSIONS R = yra., Aurelia aurita has a worldwide dis­ where Ris the estimated density, y is the tribution. The occurrence of swarms of mean number of moon jellyfish aggrega­ adult medusae varies seasonally among tions observed per day, and a is the mean geographical locations (Gunter 1950, are~ sampled per day. The standard error Loosanoff 1962, Franks eta/. 1972, Burke of R (Cochran 1977) was estimated by: 1975, 1976, Fotheringham 1980, Moiler 2 se(R) =[1/(n1f2a)] [(Iyf- 2Riyiai t RIaf) I (n -1)]1/2 1984, Veer 1985). In our survey, moon where n is the number of survey days (i) jellyfish aggregations were observed in per study area. Approximate 95% con­ each study area and were most abundant fidence intervals were estimated as R during the fall. Moon jellyfish aggrega­ ~Ius or minus twice the standard error of tions in the three study areas west of the R. Mississippi River were not common in either spring or fall, but abundance RESULTS greatly increased east of the Mississippi Estimated Aurelia aggregation den­ River in the fall (Fig.1) and the greatest sities varied greatly between spring and density was found in the North-Central fall (Table 1). In the spring, moon jellyfish Gulf study area. were observed offshore only in the south Fall sightings in the North-Central Texas study area (0.27 aggregations/ Gulf inshore waters, where temperatures 2 100 NM ), and inshore only in the North­ and salinities vary greatly among seasons, Central Gulf area (0.11 aggregations/ were common. Franks et a/. (1972) be­ 2 100 NM ). lieved moon jellyfish were limited to high Fall aggregations of near-surface salinity waters. However, Gunter (1950) moon jellyfish were much more abun­ found the jellyfish in waters with salini­ dant. Except in south Texas, Aurelia were ties as low as 16.0 ppt. We observed observed in all offshore study areas. The them both offshore, in oceanic salinities, only inshore sightings were in the North­ as well as inshore, in areas where salini­ Central Gulf study area. Fall offshore ties were greatly influenced by fresh densities ranged from 0.06 aggregations/ water runoff. In the winters of 1969-70 100 NM2 (Louisiana study area) to 5.57 and 1970-71, moon jellyfish were taken in aggregations/100 NM 2 (North-Central the inshore waters of the Mississippi Gulf study area). The North-Central Gulf Sound where salinities ranged from 29.2 density estimate was several times to 31.6 ppt (Burke 1975). Burke (1976) greater than that of any other study area. again found moon jellyfish in the winters We flew several transects, especially of 1971-72 and 1972-73 at stations on in the North-Central Gulf study area, both the north and south sides of the where moon jellyfish aggregations in the Mississippi barrier islands. He noted that https://aquila.usm.edu/goms/vol11/iss1/7 2 DOI: 10.18785/negs.1101.07 Roden et al.: Aspects of the Ecology of the Moon Jellyfish, Aurelia aurita, in Northeast Gulf Science Vol. 11, No. 1 July 1990 65

Table 1. Areas studied in 1987 and seasonal densities of offshore moon jellyfish aggregations. Density estimates (R) are aggregations per 100 square nautical miles and (seR) are the standard errors of the density estimates. Spr!ng Fall Study Area Month R (seR) Month R (seR)

South Texas April 0.27 (0.15) September 0 North Texas May 0 September 0.13 (0.08) Louisiana April 0 October 0.06 (0.07) North-Central Gulf May 0 September 5.57 (1.29) North Florida June 0 November 1.14 (0.36) Central Florida not studied November 1.42 (0.40) South Florida July 0 December 0.27 (0.16)

thousands of Aurelia were present in the soft mud to sandy-mud substrates and Mississippi Sound in December 1966, but the rarity of solid substrata, especially were "peculiarly absent from Mississippi inshore, in the North-Central Gulf study waters until the winter of 1969" (Burke area have been considered unsuitable for 1975). moon jellyfish larval development (Burke Shepherd (1969) believed moon 1976). Examination of dredge samples, jellyfish medusae were passively aggre­ oyster reefs, emplaced artificial reefs gated by wind and waves and spawning and fouling plates failed to produce occurred at that time. Brewer (1978) sessile Aurelia larvae (Burke 1975, 1976). suggested that sessile stages of marine During our aerial surveys, if other invertebrate larvae do not randomly marine animal species were observed settle but rather they select suitable within a moon jellyfish aggregation, or substrates for attachment. However, the on the periphery of an aggregation, it

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C.FL

GULF OF MEXICO

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00 ~ Figure 1. Aerial survey areas in the eastern Gulf of Mexico and locations of moon jellyfish aggrega­ tions (circles) sighted during the fall, 1987 surveys.

Published by The Aquila Digital Community, 1990 3 Gulf of Mexico Science, Vol. 11 [1990], No. 1, Art. 7 66 Short papers and notes was considered as associated with the component of the ecosystem. Further aggregation. Sharks were most commonly research on these large aggregations, as associated. Bottlenose dolphins were well as the impact of Aurelia as preda­ the second most common associate and tors, protectors, and/or prey, on juvenile sea turtles were the third most common­ fish and sea turtles, is needed. ly associated animal. Most of the associated sea turtles ACKNOWLEDGMENTS were identified as loggerhead sea turtles (Caretta caretta). However, during an The authors thank Dr. Andrew Kem­ earlier fall 1986 pilot study, several merer, Mr. Joe Benigno, Dr. Bob Shipp leatherback sea turtles (Dermochelys and an anonymous reviewer for their coriacea) were observed preying on valuable comments on this paper. moon jellyfish. All 5 species of sea turtles that are known to occur in the LITERATURE CITED Gulf of Mexico have been reported to prey on jellyfish (Pritchard 1979, Hopkins Arai, M.N., and D.E. Hay. 1982. Predation 1984, Dodd 1988). The North-Central Gulf by medusae on Pacific herring (Ciupea study area had one of the greatest den­ harengus pallast) larvae. Can. J. Fish. sities of sea turtles during the 1987 aerial Aquat. Sci. 39:1537-1540. surveys. In the fall survey, sea turtles Bailey, K.M., and R.S. Batty. 1983. A labor­ were relatively numerous around the atory study of predation by Aurelia Chandeleur Islands, and the moon jelly­ aurita on larval herring (Ciupea haren­ fish aggregation densitites in this study gus): experimental observations com­ area were the greatest recorded during pared with model predictions. Mar. the surveys. Sea turtles may have been Bioi. 72:295-301. responding to an abundance of prey. Brewer, R.H. 1978. Larval settlement The factors that regulate the appear­ behavior in the jellyfish Aurelia aurita ance, distribution, and densities of adult (Linnaeus) (Scyphozoa: Semaeostomeae). Aurelia aggregations are not well under­ Estuaries 1:120-122. stood. Moon jellyfish are voracious Burke, W.O. 1975. Pelagic cnidaria of feeders on zooplankton and larval fish Mississippi Sound and adjacent waters. (Arai and Hay 1982, Bailey and Batty Gulf Res. Repts. 5:23-38. 1983). Moiler (1984) and Veer (1985) noted Burke, W.O. 1976. Biology and distribu­ major declines in larval fish populations tion of the macrocoelenterates of when an "outburst" of jellyfish occurred. Mississippi Sound and adjacent waters. The medusae are believed to provide pro­ Gulf Res. Repts. 5:17-28. tection, and, perhaps to a lesser extent, Caughley, G. 1977. Sampling in aerial food for a variety of small and juvenile survey. J. Wildl. Manage. 41:605-615. fish (Jachowski 1963, Mansueti 1963, Cochran, W.G. 1977. Sampling tech­ Phillips eta/. 1969). Adult moon jellyfish niques. John Wiley & Sons, Inc., New are sea turtle prey. All Gulf of Mexico sea York, NY. 462 pp. turtles are currently classed as threatened Dodd, C.K., Jr. 1988. Synopsis of the or endangered species. Aurelia may be biological data on the Loggerhead Sea an important food source for these rare Turtle Caretta caretta (Linnaeus 1758). animals. The occurrence and density of U.S. Fish Wildl. Serv., Bioi. Rep. 88(14). moon jellyfish that we obseved, especially 110pp. in the North-Central Gulf study area, in­ Fotheringham, N. 1980. Beachcomber's dicate that this species is an important guide to Gulf Coast marine life. Gulf https://aquila.usm.edu/goms/vol11/iss1/7 4 DOI: 10.18785/negs.1101.07 Roden et al.: Aspects of the Ecology of the Moon Jellyfish, Aurelia aurita, in Northeast Gulf Science Vol. 11, No. 1 July 1990 67

Publ. Co., Houston, Tex. 124 pp. Veer, H.W. van der. 1985. Impact of co­ Franks, J.S., J.Y. Christmas, W.L. Silver, elenterate predation on larval plaice R. Combs, R. Waller and C. Burns. Pleuronectes platessa and flounder 1972. A study of nektonic and benthic Platichthys flesus stock in the western faunas of the shallow Gulf of Mexico Wadden Sea. Mar. Ecol. Prog. Ser. 25: off the State of Mississippi. Gulf Res. 229-238. Repts. 4:1-148. Gunter, G. 1950. Seasonal population changes and distributions as related to Carol L. Roden, Ren R. Lohoetener, Carolyn M. salinity, of certain invertebrates of the Rogers, Keith D. Mullin, and B. Wayne Hoggard Texas coast, including the commercial National Marine Fisheries Service, Southeast shrimp. Publ. lnst. Mar. Sci. Univ. Tex. Region, Mississippi Laboratories, Pascagoula 1:8-51. Facility, Pascagoula, Miss. 39568-1207. Hopkins, S., and J. Richardson (eds.). 1984. Recovery plan for marine turtles. National Marine Fisheries Service, Washington, D.C. 355 pp. Jachowski, R. 1963. Observations on the moon jellyfish, Aurelia aurita, and the spider crab, Ubinia dubia. Chesapeake Sci. 4:195. Jolly, G.M. 1969. Sampling methods for aerial census of wildlife populations. E. African Agric. For. J. 34:46-49. Loosanoff, V.L. 1962. Jellyfishes and related animals. U.S.D.I. Fishery Leaflet 535, Washington, D.C. 9 pp. Mansueti, R.J. 1963. Symbiotic behavior between small fishes and jellyfishes, with new data on that between the Stromateid, Peprilus a/epidotus, and the Scyphomedusa, Chrysaora quin­ quecirrha. Copeia 1963:40-80. Moiler, H. 1984. Reduction of a larval her­ ring population by jellyfish predator. Science 224:621-622. Phillips, P.J., W.D. Burke and E.J. Keener. 1969. Observations on the trophic sig­ nificance of jellyfishes in Mississippi Sound with quantitative data on the associative behavior of small fishes with medusae. Trans. Amer. Fish. Soc. 98:703-712. Pritchard, P.C.H. 1979. Encyclopedia of turtles. T.F.H. Publications, Inc., Nep­ tune, N.J. 895 pp. Shepherd, E. 1969. Jellyfishes. Lothrop, Lee and Shepard Co., New York. NY. 64 pp.

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