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 recovered. 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 cleanup activities.
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.
Marbled murrelets were declining in the Sound before the oil Spill, and the decline has continued since the Spill. In PWS, it is estimated that marbled murrelets declined at a rate of 5% per annum from 1989-2012, a cumulative population loss of -69%. 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. Their dietary preferences and foraging areas make significant contact with lingering oil unlikely and there are no differences in population trends between oiled and unoiled areas. 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 have not met their recovery objective of an increasing or stable population. They are considered to be not recovering from the effects of the Spill.
Click HERE for more information on Trustee Council funded studies of marbled murrelet.