Marbled Murrelet
Injury
Marbled murrelets are found throughout the northern Gulf of Alaska and are known to concentrate in Prince William Sound. Carcasses of nearly 1,100 Brachyramphus murrelets were found after the spill, and about 90 percent of the murrelets that could be identified to the species level were marbled murrelets. Since they are a small bird and not easily seen, many more murrelets probably were killed as a result of the oil than were found. Estimates vary but between 2,900 and 14,800 individuals were killed by the initial oiling and this represented 6–12 percent of the marbled murrelets in the spill area. In addition to direct mortality, foraging activity and behavior was likely disrupted during the clean-up activities.
Recovery Objective
Marbled murrelets will have recovered when their population has recovered to a level had the spill not occurred. Sustained or increasing productivity within normal bounds will be an indication that recovery is underway.
Recovery Status
Marbled murrelets were declining in the Sound before the oil spill, and the decline has continued since the spill. It is listed as a threatened species in Washington, Oregon, California and British Columbia. Marbled murrelets have low intrinsic productivity and a slow population growth rate. Therefore, recovery from an acute loss will likely take many years.
Marbled murrelets rely on forage fish such as Pacific herring and Pacific sand lance, which may be declining in the spill area due to various reasons including a potential link to EVOS. Their dietary preferences and foraging areas make significant contact with lingering oil unlikely. Exogenous factors such as climatic factors, decreases in habitat availability, and shifts in forage fish populations are the most likely drivers of murrelet population dynamics. Marbled murrelets do not meet their original recovery objective of increasing or stable populations. Moreover, their decline could be attributable in part to a decline in a primary food source; high-lipid forage fish, particularly sand lance and Pacific herring. Based on available data and scientific understanding, the mechanistic linkage between the oil spill, reduction in high-lipid forage fishes and the decline in marbled murrelets remains uncertain. Because of the great variability in the marbled murrelet annual census in the years after the spill, it is unlikely that the loss of even as much as 7–12 percent of the PWS population (the estimated spill mortality) would have been detectable by census techniques.
The recovery status for marbled murrelets remains UNKNOWN due to conflicting information and a lack of critical data. Further, due to the confounding effects discussed above, additional studies would likely be unable to clarify this species’ injury status.
View the Marbled Murrelet Restoration Notebook
Click HERE for more information on Trustee Council funded studies of marbled murrelet.