Excerpt from article. Kinda puts the horror of the BP Horizon into perspective. DV

Evaluating impacts of human activities on marine ecosystems is difficult when effects occur out of plain sight. The Deepwater Horizon/BP oil spill in the Gulf of Mexico was the largest in the U.S. history, but some reports implied modest environmental impacts, in part because of a relatively low number (101) of observed marine mammal mortalities. The authors estimate historical carcass-detection rates for 14 cetacean species in the northern Gulf of Mexico that have estimates of abundance, survival rates, and stranding records and their preliminary analysis suggests that carcasses are recovered, on an average, from only 2% (range: 0-6.2%) of cetacean deaths. Thus, the true death toll could be 50 times the number of carcasses recovered, given no additional information. While there are caveats to this estimate, it does provide a counterpoint to illustrate the magnitude of misrepresentation possible in presenting only observed carcass counts.

Williams R, Shane Gero, Lars Bejder, et al (2011) Conservation Letters

Special thanks to Richard Charter