Thompson, John R.

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A STUDY OF THE TEMPORAL CHANGES IN OFFSHORE MACROFAUNA IN THE NORTHERN GULF OF MEXICO DURING THE DEVELOPMENT OF THE OFFSHORE OIL INDUSTRY by John R. Thompson ABSTRACT To supplement the relatively short-term trawl studies conducted by other investigators in the OEI, a longer range study was conducted using existing data available from the Bureau of Commercial Fisheries (now the National Marine Fisheries Service). Data taken in the Northern Gulf of Mexico by the M/V Oregon and chartered vessels during the period in which the offshore oil industry was developed in Southern Louisiana were used in an effort to  detect changes in macrofau- na attributable to this buildup of estuarine and offshore oil driI1- ing and production. INTRODUCTION The fish in coastal waters of Louisiana have been studied since the first half of this century (Raymond 1905; Gunter 1935). Such studies became much more intensive during the 1950s. These primarily individual studies provide much useful information on the taxonomy, life history, and ecology of fish populations in this area. The most consistent and systematic set of data obtained during the pe- riod of oil industry growth in coastal and offshore Louisiana waters was developed by the Bureau of Commercial Fisheries (now the National Marine Fisheries Service and referred to  hereafter as BCF/NMFS). These At the time of this study, John R. Thompson was at the Department of Biology, University of Southern Mississippi, Hattiesburg, MS. 548 RICE UNIVERSITY STUDIES data, covering the 1950s and 1960s, were collected in order to assess the living marine resources in the Northern Gulf of Mexico. Chartered vessels, primarily the M/V Oregon, were used in these surveys. The data collected are reported in two "collection reports" (Springer and Bullis 1956; Bullis and Thompson 1965). METHODS AND MATERIALS For this paper, only data obtained from the Oregon cruises off the Louisiana coastline between longitudes 890301W and 92O30 'W were used. This area includes the outflow areas of the Mississippi and Atchafalaya River systems and, most importantly, the areas off Barataria and Timbalier Bays designated as the primary study area of the OEI. Records covering the period 1950 to 1965 taken at 523 stations in this area by the BCF/NMFS were used. A "station" according to BCF/NMFS designation consists of a specific set of operations-trawl haul, dredge haul, longline set or similar sampling/observation unit-at a precise, but not necessarily reoccupied, position fixed by Loran.The gear most commonly used for acquisition of the data in this study were either 40-foot (opening across the mouth) shrimp trawls as described by Bullis (1951) and later workers, or fish trawls rigged New England style with rollers (Captiva and Rivers 1960). Computer facilities (UNIVAC 9200) at the BCF/NMFS Pascagoula, Mississippi, Laboratory were used in the compilation and analysis of these data. Computer analyses covered only the dominant (by abundance or percentage of occurrence) fishes and shellfishes. Distribution densities and availability densities of these dominant species were used to identify any trends in the populations and their distributions that might be associated with oil drilling and production activity. RESULTS The total species complement collected and used for analysis in this study was 630 fish, 146 mollusk, and 234 crustaceans. Computer analyses revealed that eight species of fish were most abundant, with Sciaenids being the dominant group present (table 1). Offshore, blue crabs, brown shrimp, and rock shrimp were found to be the dominant crustaceans taken. Studies of annual populations and distributions revealed no significant trends over the period 1960-1965. Variations in the data were well within those expected in trawl operations, and no consistent changes were evident over this time span. OFFSHORE MACROFAUNA T a b l e  1. P r e d o m i n a n t  F i s h e s  a n d  I n v e r t e b r a t e s  i n  C a t c h e s  f r o m  M/V OREGON T r a w l  Work -- 1950-65. F i s h e s  S c i e n t i f i c  Name Common Name Svnodus foetens Arius felis Leiostomus xanthurus Micropogon undulatus Menticirrhus americanus Cynoscion nothus Stenotomus caprinus Trichiurus lepturus L i z a r d f  i s h  S e a  C a t f i s h  s p o t  C r o a k e r  S o u t h e r n  K i n g f i s h  S i l v e r  S e a - T r o u t  L o n g s p i n e  P o r g y  A t l a n t i c  C u t l a s s f i s h  I n v e r t e b r a t e s  Callinectes danae O f f s h o r e  b l u e  c r a b  Penaeus aztecus Brown s h r i m p  Sicyonia brevirostris Rock s h r i m p  The seasonal variations apparent from study of the data were those well known to commercial fisherman and as reported by Russian fleets conducting exploratory operations in the area (Sal'nikov 1969). Lowest catches occurred in June and early July (though least effort was ap- parently expended during these months) and highest catches occurred in winter (November-March). DISCUSSION The BCF/NMFS data used in this study were taken in an area off- shore described by Gunter (1963) as the "Fertile Fisheries Crescent." The "Crescent" extends from Pascagoula, Mississippi, to Port Arthur, Texas. I t  is reputed to be among the most productive fisheries areas in the world (Roithmayr 1965; Gunter 1967; Perrett et al. 1971; Juhl et al. 1973). It is estimated that 90070, by weight, of the fish species commercially har- vested from the Gulf of Mexico are estuarine dependent (Gunter 1938a, 550 RICE UNIVERSITY STUDIES 1938b). A similar estuarine dependence exists for most crustaceans in- cluding commercially important blue crabs and penaeid shrimp. Since the most sensitive period in these organisms' life cycle (eggs and larvae) is associated with the bays and sounds, any adverse effects on these en- vironments resulting from oil drilling and production should have maximum effect on abundance and community structure. In addition to the possible introduction of effluents from oil drilling and production (drilling mud, crude oil, etc.), these activities also in- troduce a physical change in the environment. It is generally accepted that artificial structures, such as oil platforms, attract and concentrate fish populations. Unless the effect of effluents is more significant, this effect on populations should be observable. Trawls studies directed t o  investigating this possibility were conducted under another OEI in- vestigation by Mr. Allison Perry. Extensive studies by the Louisiana Wildlife and Fisheries Commission (Duffy 1968) concluded that sport fishing was enhanced by the artificial reef effect of the numerous oil production platforms in the coastal and offshore waters. CONCLUSIONS No correlations could be demonstrated between macrofauna populations and oil related activities in the time period and area covered in this study. Seasonal or "natural variability" best correlates with the data. An offshore groundfish fishery was deveIoped during the period of data collection (Roithmayr 1965). The dominant group of fishes sup- porting this industry (Sciaenids) is the same group shown to be dominant in the BCS/NMFS data. These data and groundfish catch history show that the populations of fishes offshore of the OEI study are sufficient to sustain a large-scale groundfish industry. The value of the BCF/NMFS data for the correlations made in this study could have been improved through greater standardization and an increase in sampling density. This would enhance the statistical validity of the studies as well as provide a more comprehensive basis for the detection of either transient or consistent trends in populations and their distributions. ACKNOWLEDGMENTS Three senior graduate students at the University of Southern Mississippi are responsible for  much of the background work upon which the results and discussion herein rest: OFFSHORE MACROFAUNA 55 1 Nicholas Funicelli, Larry L. Massey, and Thomas McElwain. Students Louis Eaton and Vincent Guido also contributed in the early stages of the study, and many others con- tributed to stimulation of thought and aid in various facets. The National Marine Fisheries Service, Southeast Fisheries Center, supplied data printouts and computer usage. Richard B. Roe of NMFS, Washington, D.C., was particularly helpful in this, as was his technician, Judith Gatlin. REFERENCES CITED Bullis, J .  R., Jr. 1951. Gulf of Mexico shrimp trawl designs. U.S. Department of the In- terior, Fishery Leaflet 394. and John R. Thompson. 1965. Collections by the Exploratory Fishing Vessels Oregon, Silver Bay, Cornbat, and Pelican Made During 1956-1960 in the Southwestern North Atlantic. U.S. Department of the Interior, Special Scientific Report, Fisheries No. 510. Captiva, Francis J .  and Joaquim B. Rivers. 1960. Development and use of the otter- trawling gear for red snapper fishing in the Gulf of Mexico, June 1957-May 1959. Commercial Fisheries Review 22(10): 1-14. Duffy, McFadden. 1968. Sport fishing along the Gulf Coast. Louisiana Conservationist, Sept.-Oct., pp. 15-18. Gunter, G. 1935. Records of fishes rarely caught in shrimp trawls in Louisiana. Copeia 1:39-45. 1938a. Seasonal variations in abundance of certain estuarine and marine fishes in Louisiana, with particular references to life histories. Ecological Monographs 8(3):313-346. ---- 1938b. The relative numbers of marine fishes on the Louisiana coast. American Naturalist 72:77-83. ----- 1963. The fertile fisheries crescent. Mississippi Academy of Sciences Journal 9:286- 290. 1967. Some relationships of estuaries t o  the fisheries of the Gulf of Mexico. In Estuaries. American Association for the Advancement of Science 83:621-638. Juhl, Rolf, Elmer J .  Gutherz, Charles M. Roithmayr, and Gary M.  Russell. 1973. South- east groundfish program status report to the Gulf States Marine Fisheries Commission, October 1973. Perrett, William S., Barney B. Barrett, Walter R. Latapie, Judd F. Pollard, Woodrow R .  Mock, Gerald B. Adkins, Wilson J. Gaidry, and Charles J .  White. 1971. Cooperative Gulf of Mexico Estuarine Inventory and Study, Louisiana. Phase I. Area Description and Phase IV. Biology. Louisiana Wildlife and Fisheries Com- mission. Raymond, R. I. 1905. The Fishes of Louisiana. M.S. thesis, Tulane University. Roithmayr, Charles M. 1965. Industrial Bottomfish Fishery of the Northern Gulf of Mexico. 1959-1963. U.S. Department of the Intetior, Special Scientific Report, Fisheries No. 518. Sal'nikov, N. E. 1969. Fishery research in the Gulf ilf Mexico and the Caribbean Sea. In A. S. Bogdanov, ed., Society-Cuban Fishery Research, translation by U.S. Department of the Interior, NSF, pp. 78-171, Israel Program for Scientific Transla- tions. Springer, Stewart and Harvey R. Bullis, Jr .  1956. Collections by the Oregon in the Gulf of Mexico. U.S. Department of the Interior, Special Scientific Report, Fisheries No. 196. 

A Study of the Temporal Changes in Offshore Macrofauna in the Northern Gulf of Mexico During the Development of the Offshore Oil Industry

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A Study of the Temporal Changes in Offshore Macrofauna in the Northern Gulf of Mexico During the Development of the Offshore Oil Industry

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