Some effects of No. 2 fuel oil on the brown shrimp Penaeus aztecus.

The sensitivity of brown shrimp of three size groups to water-soluble fractions of No. 2 fuel oil was tested. Total oil hydrocarbons present were determined by infrared spectrophotometry. Post-larvae 9-12mm long were less sensitive than were two larger sizes of juveniles. Shrimp of two size classes, were exposed to 1.3 ppm water-soluble fractions of No. 2 fuel oil for 20 hours and then placed in oil-free water for 6 hours. Tissue and water levels of three toxic diaromatics: naphthalene, methylnaphthalene, and dimethylnaphthalene, were determined by ultraviolet spectrophotometry. For both size classes, maximum uptake of all three compounds occurred within the first exposure hour and depuration began during the 20 hour exposure period. Within one hour exposure larger shrimp had absorbed approximately 4 times as much of the three diaromatics as did smaller shrimp, but depurated more rapidly, having less of each diaromatic after 20 hours of exposure. Complete depuration of the three diaromatics occurred between 5 and 10 days for large shrimp and 25 and 33 days for small.