ABSTRACT

A common practice in the mariculture of shrimp on the Texas coast is the application of fuel oil on the surface of the pond. This thin oil layer serves to eliminate large aquatic insects which are predators of the small juvenile shrimp. Ordinarily, a common diesel fuel is used and it is removed from the pond after one day's treatment. In this experimental spill study, a high aromatic (38%) #2 fuel oil was utilized in higher quantity than normal and the residue was not removed. Mortalities of juvenile shrimp (Penaeus setiferus) and other invertebrates associated with the pond were recorded over a period of 96 hours following the oil treatment. A peak in the level of mortality occurred 48 hours after the spill, coinciding with the peak in the concentration of naphthalenes (naphthalene, methylnaphthalenes in the tissues of caged and free swimming organisms occurred at the point (48 hours) at which the concentration of these compounds was maximal in the water column. The concentration of naphthalenes in the sediment reached a peak approximately 12 days after the maximum peak in the tissues and water.

While the pond water and sediments studied contained measureable levels of naphthalenes, the shrimp and clams (Rangia cuneata) were shown to release a major portion of accumulated naphthalenes by day 96. Oysters and sediment measured at this same time interval showed levels between 3 and 6 parts per million (ppm) total naphthalenes. Shrimp, clams, and oysters taken to the laboratory 38 days after the spill released naphthalenes to background or near background levels. The data compiled in this study were compared to the findings of various field and laboratory investigations.

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