During the spring of 1951, the U.S. Fish and Wildlife Service undertook the removal of sea otter, Enhydra lutris (L.), from the Aleutian Island of Amchitka, for the purpose of restocking range from which the animals have long been exterminated. The decision to undertake this activity was influenced by the nature of military operations planned for the island later the same year. The capture and removal of the otter were under the supervision of Mr. Robert D. Jones, Biologist, U.S. Fish and Wildlife Service. Heavy losses among the animals shortly after capture made the venture unsuccessful. Many deaths were concurrent among animals in the wild state. The writer was asked to investigate the causes of disease in the sea otter, and it is the purpose of this paper to report the results of these investigations.
According to the work of Rausch (1953) , two species of helminth parasites, Porrocaecum decipiens (Krabbe, 1878) and Microphallus pirum (Afanas'ev, 1941), are pathogenic for the sea otter, Enhydra lutris (L.) , on the Aleutian Island of Amchitka. In continuation of investigations of sea otter mortality on Amchitka during the latter part of May and early June, 1952, the writer made an attempt to
obtain information on the life cycles and developmental characteristics of these parasites. It is the purpose of this paper to report the results of these observations.
The immediate ecological changes resulting from the nuclear detonation Milrow seem to have been relatively small in comparison to the effects associated with site preparation and other operational activities. Testtime studies, conducted by Battelle's Columbus Laboratories and subcontractors, designed to detect and measure the effects of Milrow are described and the changes that have been detected are summarized. The long-term ecological effects of Milrow are the subject of several continuing investigations.
Marine mammals being among the top predators in the food web tend to accumulate organic and inorganic contaminants from the environment. The body burden of contaminants in these species could reflect their foods and thus contaminant levels could serve as proxies on the changes of ecosystem. A pilot study was carried out to investigate the possibility of radionuclide leakage at Amchitka using a suite of sea otter (Enhydra lutris) skulls collected near Amchitka nuclear test-sites before (1950s) and after the testing (1990s), and at Adak, another Aleutian Island, about 300 km from Amchitka, where the potential impact of radionuclide leakage from Amchitka is expected to be negligible. In addition, the naturally occurring and anthropogenic radionuclide content on the sea otter skull was also utilized to investigate if there was any significant ecosystem changes in the environment. Concentration of 210Pb in sea otter bones collected during the 1950s was significantly higher than those collected in the 1990s. We propose that among the various factors that could cause this higher enrichment in 210Pb, changes in the sea otter prey is the most likely one. Comparison of the 137Cs, 90Sr, 239,240Pu concentrations appear not to be significantly higher in sea otter skulls collected in 1990s from Amchitka where the underground tests in 1965-71 than those from Adak, although significant differences were detected among different groups collected at various times.