A rough estimate of ghost shrimp (Neotrypaea californiensis) population characteristics in False Bay, San Juan Island, Washington

Abstract

Neotrypaea californiensis are a burrowing decapod species that acts as an important ecosystem engineer and bioturbator in intertidal sandflats. Using a novel sampling method, the abundance of N. californiensis individuals was estimated for two sites in False Bay, San Juan Island, Washington. An equation for the biomass of an individual given the carapace length was derived from a regression of logarithmic carapace length and logarithmic mass and used to estimate the biomass of N. californiensis across both sample sites. Sediment samples were taken and subjected to a volume ratio analysis to quantify the percentage of sediment grain size that fell into >2mm, 2mm-0.5mm, and <0.5mm categories for each sample point. The influence of surface sediment grain size, beneath-surface sediment grain size categories, percent Ulva cover, and number of surface species on the spatial distribution of N. californiensis was examined using linear regressions and correlation matrices, but none were found to be significantly correlated or explanatory for the spatial distribution of individuals.