The types of contaminants that will most likely be detected with mortality incident data are those that can be easily measured, leave a detectable residue, or have an acute effect on organisms. The best indicator would be a sentinel species that shares common traits with the critically important species. These species have a limited range, limited dispersal, and are density independent. Sentinel species are common, widely distributed, typically do not have narrow habitat requirements, and match a trophic level of a species of concern. Incident data should not be used alone for inferring geographical or temporal trends because of the many inherent systematic biases.
Trends can reflect changes or varied levels of effort in collecting data.
Personal bias can occur at many points in documenting a mortality incident, such as recording field information and interpreting diagnostic findings. Individuals who record mortality incidents need guidance and improvement so that they can record the information that is needed to make extrapolations to the population levels. Narrative data are important but not practical for easy data entry. A full narrative of the incident is needed so others can examine the record and get the information they need to understand the entire incident. Background details may be very important in quality evaluation or in differentiating contaminant vs. unknown causes of mortality.