EXXON VALDEZ Oil Spill Restoration Project Final Report Shock Resistance and Observer Classification of Pink Salmon Eggs (Restoration Project 01492)

摘要

After the 1989 Exxon Valdez spill, pink salmon (Oncorhynchus gorbusha) embryo mortality was greater in oiled streams than in reference streams. The possibility that systematic, sampler-induced errors explain these differences is compared to an alternative hypothesis, oil toxicity. Resistance to hydraulic shock in a naturally-spawned pink salmon egg population increased more slowly than in uniform-aged eggs as a result of mixed embryo ages. The number of eggs that died from natural causes was unrelated to sample time. The most common observer errors were misclassification of shocked eggs as live (equal to or less than 9 plus or minus 1%) or as dead (equal to or less than 4.6 plus or minus 1%). When observation times were restricted to 0.5 h, < 3% of shocked eggs were classified as dead. Combining our observations with modeled estimates of the magnitude of observer error required to eliminate statistical differences between oiled and reference streams, we found these potential errors were insufficient to explain survival differences in Prince William Sound streams.