Accumulation of DDT Residues in Triphoturus mexicanus from the Gulf of California

Abstract

CONTAMINATION of marine fish by chlorinated hydrocarbons, especially by DDT and its congeners^*, could threaten their future or continued utility as a food source if residues accumulate to the point of incipient toxicity on detrimental sublethal effects¹. Little is known about the distribution of DDT residues in marine fish beyond listed concentration values for certain species. Most investigations have dealt with concentrations of residues in tissues or large pooled, unsorted samples of commercially caught fish (refs. 3 and 4; the latter covers exclusively marine studies). From this limited information, we know that fish of a single species caught 111 adjacent areas have markedly different contents of residues, probably because of differences in the magnitude of local sources of estuarine or airborne pesticides^2–5. This heterogeneity of exposure poses problems for the interpretation of residue data from fish caught in these areas. In an attempt to obtain size-class data about concentrations of residues, relatively free from the effects of pesticide “hot spots”⁶, Triphoturus mexicanus, a midwater fish from an area relatively remote from areas of pesticide application, was chosen for analysis.