Photo Credit: Mark Henspeter

Studying the Past


Retrospective analyses allow us to put the data collected during this short-term study into context by examining patterns in historical data collected over the past few decades.  Examining long-term patterns allows us to ask informed questions about the possible environmental drivers of fish survival and recruitment in the Gulf of Alaska.  

Further Details

Studying patterns in data collected in the same manner over long periods of time (called time-series) allows us to see how much things typically change over time and also allows us to identify points in time when changes are out of the ordinary.  For example, natural variability may cause a measurement like water temperature to be a little higher in some years and a little lower in other years, and that variation may not be enough to cause effects on fish survival.  We need to know how much change is natural in order to identify years when changes are extreme.  If we can identify extreme years, we may be able to find a link to fish survival.  Ultimately we are trying to identify a few environmental measurements that can be monitored to predict fish recruitment, which allows scientists to better predict future abundances and managers to set more appropriate quotas for fisheries. 

Photo Credit: Carl Johnson

Retrospective analyses are being conducted on a variety of types of data.  Sea surface temperature and chlorophyll concentrations have been measured via satellite over decades, and we are putting together multiple streams of data to create a continuous time series and identify important patterns in space and time.  Other analyses include salinity, climate indicators, plankton and fish distribution, and others.