Showing papers by "Robert L. DeLong published in 2009"
TL;DR: Results suggest that domoic acid contributes to reproductive failure on California sea lion rookeries, and the etiology of abortion and premature parturition was varied.
Abstract: Domoic acid is a glutaminergic neurotoxin produced by marine algae such as Pseudo-nitzschia australis. California sea lions (Zalophus californianus) ingest the toxin when foraging on planktivorous fish. Adult females comprise 60% of stranded animals admitted for rehabilitation due to acute domoic acid toxicosis and commonly suffer from reproductive failure, including abortions and premature live births. Domoic acid has been shown to cross the placenta exposing the fetus to the toxin. To determine whether domoic acid was playing a role in reproductive failure in sea lion rookeries, 67 aborted and live-born premature pups were sampled on San Miguel Island in 2005 and 2006 to investigate the causes for reproductive failure. Analyses included domoic acid, contaminant and infectious disease testing, and histologic examination. Pseudo-nitzschia spp. were present both in the environment and in sea lion feces, and domoic acid was detected in the sea lion feces and in 17% of pup samples tested. Histopathologic fin...
76 citations
TL;DR: In this paper, the authors present a survey of the National Museum of Natural History, Smithsonian Institution, Washington, DC and the National Oceanographic and Atmospheric Association (NOAA) of the Alaska Fisheries Science Center.
Abstract: ∗National Museum of Natural History, Smithsonian Institution, Washington, DC †Alaska Fisheries Science Center, NOAA ‡University of Oregon, Eugene, Oregon ∗∗Humboldt State University, Arcata, California ††California Polytechnic State University, San Luis Obispo, California ‡‡University of Oregon, Eugene, Oregon §University of California, Los Angeles, California ¶University of California, Santa Barbra, California
32 citations
Abstract: Found in ocean and other aquatic ecosystems around the world, seals and sea lions (pinnipeds) spend significant time on land, often congregating in large rookery (breeding) and haul out sites. Alth...
8 citations
01 Jan 2009
TL;DR: Stable isotope analysis of various tissues can provide dietary information at the individual level on different temporal and spatial scales, as well as reveal patterns of the foraging ecology among groups of animals.
Abstract: Stable nitrogen and carbon isotope analyses have increasingly been used to investigate the foraging ecology of marine mammals, particularly in response to the limitations of using conventional dietary analysis techniques. In this study, we compared nitrogen (δ15N) and carbon (δ13C) values of four different tissues (i.e., fur, red blood cells, serum, and plasma) from California sea lions (Zalophus californianus; n = 58) of various age classes (i.e., pup, yearling, juvenile, and adult). Metabolically active tissues with relatively high turnover rates (plasma and serum) had similar δ15N and δ13C values, but these two tissues had significantly higher δ15N values and lower δ13C values in comparison to red blood cells or fur. In general, δ15N values decreased with increasing age; δ15N values for pups were between 1.2‰ (fur) to 2.0‰ (serum) greater in comparison to adult females. In general, δ13C values increased with age (except red blood cells). Pups had mean δ13C values that were 0.4‰ (plasma) to 0.5‰ (fur and serum) lower than mean values of adult females. Stable isotope analysis of various tissues can provide dietary information at the individual level on different temporal and spatial scales, as well as reveal patterns of the foraging ecology among groups of animals.
5 citations
01 Jan 2009
TL;DR: In this paper, archeological evidence suggests that Guadalupe fur seals were the focus of Late Holocene hunters, with less numbers of California sea lions, harbor seals, and sea otters.
Abstract: —Archaeological evidence suggests that pinnipeds and sea otters have long been importantdietary and raw material resources fo r Channel Islanders. Excavations at a village site on the south coast ofSan Miguel Island, CA-SMI-232, provide evidence of sea mammal hunting at about 1200 cal BP. Detailedanalysis demonstrates that Guadalupe fur seals were the focus of Late Holocene hunters, with lessernumbers of California sea lions, harbor seals, and sea otters. Since federal protection and the subsequentrebound in populations after historic over-hunting, tens of thousands of pinnipeds haul out each year onSan Miguel Island beaches and rocky outcrops. Today, breeding populations are dominated by northernelephant seals, California sea lions, northern fur seals, and harbor seals with occasional visits by Steller’ssea lion and Guadalupe fur seals. The archaeological record suggests a complex picture of local pinnipedpopulation dynamics that has been severely altered by historic exploitation, and perhaps by large-scaleprehistoric hunting. In this paper, we present zooarchaeological evidence of pinniped hunting from CA-SMI-232 and document significant changes between pr ehistoric and modern pinniped communities on SanMiguel Island.
4 citations