Temperature is one of the most important factors defining the habitat of marine organisms. Thermal conditions affect the growth and development of fish and shellfish, and differentially affect the survival of different life stages.  Recent analyses of the amount of surface thermal habitat on the Northeast Shelf over the past 26 years reveal a trend of constricting thermal habitat ranges. Although certain thermal habitats are present year round (for example, 14°C thermal habitat is present on all days of the year (see top figure)),  extreme thermal habitats (such as 5°C or 24°C habitats) are only available during short durations, i.e. the winter and summer, respectively.  Coldest and warmest habitats have been increasing in recent years, whereas the main transitional habitats that account for most of the thermal habitat on the shelf have been declining (see bottom figure).  Hence, the thermal habitats most utilized by marine organisms on the shelf have been constricted by changes in temperature conditions.