Effects of the Ixtoc Oil Spill on the Marine Fauna in the Southern Gulf of Mexico

On June 3rd, 1979, at the Ixtoc I oil platform in the southern Gulf of Mexico, a major oil spill occurred. This incident was considered among the 3 most important oil spills in history because of the quantity of oil that was released to sea (560 million L). PEMEX (the Mexican oil company) together with the National University of Mexico (UNAM) undertook a series of surveys in the affected area in order to assess the effects of this incident on the local fauna. Prior to this incident (May to July 1978), UNAM had a sampling program in the same area using a shrimp trawl net on 21 stations at depths of 10 to 40 fathoms. Following the spill, 5 more surveys were undertaken with the same gear, from August to November 1980, and February, June and October 1981. The general conclusion was that the oil spill did not affect the distribution and diversity of fish, although the abundance decreased. However, on average the catches from the local fisheries did not change.  Approximately 100 fish species were identified, and from these only 10 species had the same importance in terms of abundance and distribution before and after the spill. For the case of the macroinvertebrates, major changes occurred following the oil spill. Samples took during 1979 and 1980 were markedly different from those taken in the same stations previous to the oil spill. Dominant taxa dropped to 47 and 41 in 1979 and 1980, from 65 and 69 during the 1976 and 1977 sampling periods. The total number of individuals also decreased; in December 1980 the number of taxa declined to about a third and the number of individuals decreased about a fifth of the numbers observed during 1976. A chromatographic analysis undertook on muscle tissue on commercial species of finfish, mollusks and crustaceans undertook in 1985, concluded that these organisms were oil free, therefore the spill did not represent a risk in terms of health due to food poisoning.