In order to understand how ocean conditions affect fish populations, researchers need to know something about the state of the water when they count fish.  Dr. Rick Starr (left) and Ichthyology student Katie Schmidt are getting ready to test the ocean temperature and clarity as part of fishing surveys with the California Collaborative Fisheries Research Program. Dr. Starr is holding a white sensor that records the temperature of the water as it is lowered from the surface.

In Katie’s hand is a secchi disc, an extremely high tech instrument that oceanographers have been using to determine water clarity since Pietro Angelo Secchi invented it in 1865.  The disc is lowered until it is no longer visible from above the water, and the point at which it disappears is the Secchi depth.  It’s cheap, simple and if it ain’t broke…