Arctic Report Card 2008: Tracking Recent Environmental Changes

There continues to be widespread and, in some cases, dramatic evidence of an overall warming of the Arctic system. Atmosphere: 5° C temperature increases were recorded in autumn Ocean: Observed increase in temperature of surface and deep ocean layers Sea Ice: Near-record minimum summer sea ice extent Greenland: Records set in both duration and extent of summer surface melt Biology: Fisheries and marine mammals impacted by loss of sea ice Land: Permafrost temperatures tend to increase, while snow extent tends to decrease The Arctic Report Card is introduced as a means of presenting clear, reliable and concise information on recent observations of environmental conditions in the Arctic, relative to historical time series records. Issued annually, it provides a method of updating and expanding the content of the State of the Arctic Report, published in fall 2006, to reflect current conditions. Some of the essays are based upon articles in the BAMS State of the Climate in 2007. Material presented in the Report Card is prepared by an international team of scientists and is peer-reviewed by topical experts of the Climate Experts Group (AMAP) of the Arctic Council. The audience for the Arctic Report Card is wide, including scientists, students, teachers, decision makers and the general public interested in Arctic environment and science. The web-based format will facilitate future timely updates of the content

Over-winter lipid depletion and mortality of age-0 rainbow trout (Oncorhynchus mykiss)

In this study we identify the size-dependent risk of winter starvation mortality as a strong selective pressure on age-0 rainbow trout (Oncorhynchus mykiss) that could promote the risk-taking behaviour and allocation of energy to lipids previously observed in young trout cohorts. Age-0 trout subjected to simulated winter starvation conditions gradually depleted lipid reserves to a critical minimum lipid content below which death occurred. Small fish with lower lipid content exhausted lipid reserves earlier, and experienced high mortality rates sooner, than larger fish with greater lipid content. Consequently, winter starvation endurance was dependent upon size-dependent lipid reserves and winter duration. To validate the laboratory findings in the field, we stocked several size classes of hatchery-raised trout with known lipid content at the start of winter into two experimental lakes, and estimated survival and lipid depletion at winter\u27s end. Larger age-0 trout had greater initial lipid reserves than smaller trout. Individuals depleted most of their lipid reserves over the winter, and experienced mortality that ranged from just under 60% for the largest individuals to just over 90% of the smallest individuals. Many survivors had lipid contents near, but none were below, the minimum lipid content determined in the laboratory.<br /