Editor Leah Gerber
Underestimating the damage: interpreting cetacean carcass recoveries in the context of the Deepwater Horizon/BP incident
Article first published online: 30 MAR 2011
©2011 Wiley Periodicals, Inc.
Volume 4, Issue 3, pages 228–233, June/July 2011
How to Cite
Williams, R., Gero, S., Bejder, L., Calambokidis, J., Kraus, S. D., Lusseau, D., Read, A. J. and Robbins, J. (2011), Underestimating the damage: interpreting cetacean carcass recoveries in the context of the Deepwater Horizon/BP incident. Conservation Letters, 4: 228–233. doi: 10.1111/j.1755-263X.2011.00168.x
- Issue published online: 7 JUN 2011
- Article first published online: 30 MAR 2011
- Received , 23 September 2010, Accepted, 15 February 2011
- Anthropogenic impacts;
- Deepwater Horizon;
- Gulf of Mexico;
Evaluating impacts of human activities on marine ecosystems is difficult when effects occur out of plain sight. Oil spill severity is often measured by the number of marine birds and mammals killed, but only a small fraction of carcasses are recovered. 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. We 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. This 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. We discuss caveats to this estimate, but present it as a counterpoint to illustrate the magnitude of misrepresentation implicit in presenting observed carcass counts without similar qualification. We urge methodological development to develop appropriate multipliers. Analytical methods are required to account explicitly for low probability of carcass recovery from cryptic mortality events (e.g., oil spills, ship strikes, bycatch in unmonitored fisheries and acoustic trauma).