Defining pelagic habitat indicators for migratory fish is particularly interesting and challenging due to the complex interaction between the marine food web and the physical variability. Through a multidisciplinary study, a group of experts in marine ecology, physical oceanography and stock assessment from the fishing industry, government and academia developed a method to explicitly account for shifting habitat distributions in fish population assessments. The study group initially developed a thermal niche model for an important short-lived pelagic forage fish, Atlantic Butterfish (Peprilus traicanthus) in the Northwest Atlantic Ocean. This niche model was coupled to a hindcast of daily bottom water temperature derived from a de-biased regional numerical ocean model (ROMS) in order to project thermal habitat suitability in the Northwest Atlantic on a daily basis over the last 40 years. The hindcast of thermal habitat suitability was used to estimate the proportion of thermal habitat suitability available on the Northeast US continental shelf that was sampled on fishery-independent surveys conducted during the spring and fall. We were able to create 40 years of daily maps of predicted butterfish thermal habitat suitability. This time series of Habitat Suitability was then used to determine a time dependent availability, or stock range, based on butterfish thermal niche space. The time dependent availability was then provided to the stock assessment scientists for inclusion in the model.