The capelin (Mallotus villosus) stock inhabiting NAFO Divisions 2J3KL spend most of their adult life in offshore waters. Historically the center of this distribution changed seasonally with capelin generally found further north (NAFO Divisions 2J and 3K) in the fall of the year, moving southward to spawn along the northeast Newfoundland coast in the spring and early summer. Over the years, a number of indices have been used to describe the abundance and distribution of capelin off Newfoundland. These include: inshore data series which have typically concentrated on capelin abundance at or around the time of spawning (aerial surveys, inshore commercial fishery catch rates, egg depositions), directed offshore acoustic surveys, annual offshore pelagic 0-group surveys, and to a lesser extent bycatch from offshore bottom trawl surveys. Over the history of these acoustic surveys changes have occurred which may impact survey results and comparability. These included changes in the acoustic technology used, calibration techniques, fish biology, and sampling gear used. This paper will document these changes and present results of a modeling exercise designed to capture some of the uncertainty resulting from these changes and integrate it into the subsequent biomass and abundance estimations.