I saw this article and was slightly dubious as well. Some follow-up research indicates that the testing methodologies used had known error rates approaching the discrepencies detected during the analysis. That was enough to make me somewhat skeptical of the analysis, without doing the due diligence to dig any deeper into it. I would be much more comfortable if someone had a sting operation or videotaped an instance of actually substituting the fish as claimed, which should be incredibly easy considering how common they allege the substitutions are.