Reanalysis of continuous shellfish monitoring data in pursuit of temporal and spatial patterns of paralytic shellfish toxins in the Puget Sound/Salish Sea

Harmful algal blooms (HABs) are of growing concern on the West Coast of North America. The dinoflagellate Alexandrium catanella is known to produce toxins that have the potential to concentrate in shellfish and, when consumed by humans or marine mammals, may result in Paralytic Shellfish Poisoning (PSP) leading to illness or death. In Puget Sound, the Washington State Department of Health (WDOH) collects and tests shellfish samples to protect the health and safety of shellfish consumers as well as the livelihood of the extensive local shellfish industry. Such data have been collected since the 1950s. We analyze data from 2003 to 2016 which can be mapped onto standard indicator sites for bi-weekly time series and spatial analysis. Our analysis uses a combination of simple regression and visual assessment of maps and graphs to describe patterns within subbasins, as well as larger-scale patterns within the Salish Sea. We also make spatial comparisons between the annual initiation of toxic shellfish beds and A. catanella benthic cyst concentrations. By determining the presence or absence of spatial or temporal trends, we hope to contribute to shellfish sampling efficacy and efficiency, help prioritize shellfish sampling and location, and thereby reduce the risk of human consumption of Paralytic Shellfish Toxins