Line transect estimates of Short-tailed Shearwater <i>Puffinus tenuirostris</i> mortality in the south-eastern Bering Sea, 1997-1999. Hyrenbach, K., Baduini, C., & Hunt Jr., G. Marine Ornithology, 29(1):11–18, Point Reyes Bird Observatory-Marine, 4990 Shoreline Highway, Stinson Beach, CA 94970, United States, 2001.
abstract   bibtex   
During 1997, hundreds of thousands of Short-tailed Shearwaters Puffinus tenuirostris starved to death in the Bering Sea. We surveyed the distribution and abundance of floating carcasses during a cruise between 27 August-12 September, and estimated that over 95 000 carcasses were afloat within three survey grids covering approximately 52 400 km2. We repeatedly surveyed the same areas during two subsequent cruises in 1998 and 1999, and used standard population sampling techniques to evaluate the background levels of shearwater mortality during additional years when a die-off did not occur. The mortality event we observed in 1997 was unusual due to its extent and magnitude. During the die-off, dead shearwaters were sighted within all three survey grids. Conversely, we only encountered carcasses at one of these sites in 1998. Moreover, carcass densities in 1997 were at least one order of magnitude higher than those recorded during the following year. Surveys of seabird mortality at sea can account for floating carcasses before they are lost through advection and scavenging. Therefore, vessel-based surveys are likely to improve the accuracy of seabird mortality estimates based solely on counts of beach-cast carcasses. Here we describe the use of line transects to estimate seabird mortality at sea, and offer suggestions to standardize future surveys. Standardized surveys will improve our ability to compare the frequency, extent, and magnitude of seabird die-offs over time.
@ARTICLE{Hyrenbach2001,
  author = {Hyrenbach, K.D. and Baduini, C.L. and Hunt Jr., G.L.},
  title = {Line transect estimates of Short-tailed Shearwater \textit{Puffinus
	tenuirostris} mortality in the south-eastern Bering Sea, 1997-1999},
  journal = {Marine Ornithology},
  year = {2001},
  volume = {29},
  pages = {11--18},
  number = {1},
  abstract = {During 1997, hundreds of thousands of Short-tailed Shearwaters \textit{Puffinus
	tenuirostris} starved to death in the Bering Sea. We surveyed the
	distribution and abundance of floating carcasses during a cruise
	between 27 August-12 September, and estimated that over 95 000 carcasses
	were afloat within three survey grids covering approximately 52 400
	km2. We repeatedly surveyed the same areas during two subsequent
	cruises in 1998 and 1999, and used standard population sampling techniques
	to evaluate the background levels of shearwater mortality during
	additional years when a die-off did not occur. The mortality event
	we observed in 1997 was unusual due to its extent and magnitude.
	During the die-off, dead shearwaters were sighted within all three
	survey grids. Conversely, we only encountered carcasses at one of
	these sites in 1998. Moreover, carcass densities in 1997 were at
	least one order of magnitude higher than those recorded during the
	following year. Surveys of seabird mortality at sea can account for
	floating carcasses before they are lost through advection and scavenging.
	Therefore, vessel-based surveys are likely to improve the accuracy
	of seabird mortality estimates based solely on counts of beach-cast
	carcasses. Here we describe the use of line transects to estimate
	seabird mortality at sea, and offer suggestions to standardize future
	surveys. Standardized surveys will improve our ability to compare
	the frequency, extent, and magnitude of seabird die-offs over time.},
  address = {Point Reyes Bird Observatory-Marine, 4990 Shoreline Highway, Stinson
	Beach, CA 94970, United States},
  comment = {http://www.marineornithology.org/PDF/29_1/29_1_3.pdf},
  file = {Hyrenbachetal2001.pdf:Hyrenbachetal2001.pdf:PDF},
  keywords = {Bering Sea, Distance sampling, Line transects, Puffinus tenuirostris,
	Seabird die-offs, Seabird mortality estimates, Seabird population
	monitoring, Short-tailed Shearwater},
  owner = {eric},
  subdatabase = {distance},
  timestamp = {2006.11.22}
}
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