Dataset on the shell traits of the California mussel Mytilus californianus

This dataset is a geographic survey of Mytilus californianus mussel shell traits. Mussels were collected from wave-exposed rocky headlands in 2023-2024 under CA Fish & Wildlife Scientific Collecting Permits S-191200004-19122-001 and S-190980002-23226-001, CA State Parks permit 24-820-015 and Oregon taking permit 27976. The soft tissue was removed in the field, and the shells were cleaned with fresh water. For each mussel the length was recorded, then multiple shell metrics were calculated for the left valve. First, a shell thickness index was calculated for the entire valve (STI = 1,000*dry weight/(Length*(pi/2)*(Height^2+Width^2)^0.5). Then, the shell was cut using a bandsaw and Dremel diamond wheel at 1/3 the length of the mussel from the anterior end. The cross-sections were scanned and using ImageJ the thickness of the cross sections were calculated as the area of the cross section divided by the length of the curved area. Lastly, the maximum and minimum thickness of the cross sections were measured using ImageJ, disregarding the dorsal hinge and ventral lip for the maximum and minimum thickness, respectively.