Thermal Habitat Dynamics in the Northwest Atlantic and the Role of the Winter Habitat Squeeze in Density Dependent Regulation of Forage Species Populations.

Production and age-structured assessment models assume factors regulating population
productivity are stable in space and time. Violations of this assumption are common and
affect the ability of assessment’s to predict future population size (UN FAO 2000). We
assert that many factors affecting critical processes regulating populations including
habitat volume are unstable because the underlying physical environment of the ocean is
unstable. The objective of our proposed study is then to perform empirical and
theoretical analyses required to fully develop and support this hypothesis and to develop
a useful set of indicators for ecosystem and stock assessment that rest on the ecological
mechanisms. We will develop indicators for ecosystem and stock assessment based on
mechanistic links between density dependence, thermal habitat dynamics and climate
forcing. To do this we will 1) Evaluate the temperature estimates from the 50 year
ROMS hindcast; 2) Develop thermal habitat model and estimates of thermal habitat
volume; 3) Identify NEUS fish and invertebrate stocks for which winter habitat volume
appears to modulate density dependent mortality. Identify potentially important remote
oceanographic and climate drivers of dynamic changes in winter habitat volume; and 4)
Apply modeling framework to determine ecosystem and stock indicators.