Observer classification of live, mechanically damaged, and dead pink salmon eggs

Susceptibility of pink salmon (Oncorhynchus gorbuscha) eggs to mechanical damage (shock) was studied to test the ability of observers to discriminate among live, dead, and shocked eggs. In a series of six laboratory trials, the mean error rate in discrimination did not exceed 12% and was less than or equal to 3.5% in 4 of 6 trials. The most common error was misclassification of shocked eggs as live (less than or equal to 9 +/- 1%), an error that is irrelevant in field studies designed to determine natural death rate. The second most common error was shocked eggs classified as dead (less than or equal to 4.6 +/- 1%) when observation times were unrestricted (less than or equal to 60 minutes); this was reduced to less than 0.5% when observations were limited to less than or equal to 12 minutes. Inexperienced observers were easily trained (within 1 hour) to classify eggs. To accurately describe natural systems before sample disturbance, shocked and dead egg categories should not be combined when reporting data. Publications: Thedinga, J. F., M. G. Carls, J. M. Maselko, R. A. Heintz, R. E. Thomas and S. D. Rice. 2003. Shock resistance and observer classification of pink salmon eggs. Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 01492), National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Auke Bay Laboratory, Juneau,Alaska.