A comparative assessment of contaminants in fish from four resacas of the Texas, USA-Tamaulipas, Mexico border region

A recent survey of contaminant information for the Lower Rio Grande Valley (LRGV), Texas, has shown that little is known about contaminants and their impacts on biota of resacas (oxbows) along the US-Mexico border. In 1996, f ish were collected from four resacas in the Texas-Tamaulipas border region to assess contaminant loadings and their impacts on fish and birds. Tissue residue concentrations in fish were analyzed and also compared to two histo pathological bioindicators of unhealthy environmental conditions. Of the or ganochlorine insecticides measured, DDE was the most common and was present at relatively high concentrations (10 mug/g w/w) at some sites. DDE concen trations were nearly 20 times greater in fish from resacas in Texas than fr om resacas in Tamaulipas, although the limited sample sizes obtained preclu ded statistical comparisons. DDE concentrations in fish from the two Texas resacas were also greater than those reported in fish from nearby areas dur ing the 1980s and 1990s. Most trace element concentrations were similar amo ng resacas from Texas and Tamaulipas. Arsenic, however, was two to six time s greater in fish from a downtown resaca in Matamoros than in fish from oth er resacas in Tamaulipas and Texas. The bioindicators, pigment accumulation , and macrophage aggregates (MAs), in general reflected the contamination i ndicated by the tissue residues for each site. Overall, it appears that som e resacas of the US-Mexico border region are contaminant sinks and could po se potential health or reproductive problems for fish and wildlife, and hum ans that consume fish from those sites. Published by Elsevier Science Ltd.