“Where’s Waldo?”: Unraveling the puzzle of Idotea wosnesenskii abundance across San Juan Island

Abstract

Idotea wosnesenskii are intertidal isopods typically found on kelp, mussel beds, and intertidal rocks. With a relatively large geographical range, I. wosnesenskii can be found from Alaska to northern Mexico while also appearing along the coastlines of Siberia. This study examined the influence of rock width, substrate preference, shore crab presence, and intertidal height on the abundance and distribution of I. wosnesenskii across San Juan Island. We found that aggregations of I. wosnesenskii are likely to be found under rocks with width larger than 25.6 cm (R2 = 0.36, p = 0.028). In comparison, singular individuals of I. wosnesenskii are more likely to be found under rocks with width smaller than 25.6 cm. Idotea wosnesenskii also had a substrate preference of seaweed, cobble, and bedrock (F = 10.9, p = 0.01). Shore crab presence and intertidal height had no significant effect on the abundance of I. wosnesenskii (p > 0.05). These findings may support observations from past studies that Idotea are primarily mesograzers who can also be omnivorous depending on food availability. However, further research is required to determine the full impact of shore crab presence, and intertidal height on the distribution of I. wosnesenskii.