Data from: Stable isotopes reveal minimal spatial and temporal variation in diet of the wrymouth (Cryptacanthodes maculatus)

Two intertidal mudflates in eastern Maine (Washington County) were sampled in this study: Larrabee Cove in Machiasport and Mud Hole Cove on Great Was Island, Beals. Wrymouth and potential prey were sampled in both mudflats in the spring and summer of 2013. Wrymouth were collected by walking on and around burrows to collapse them. Fish were collected when they surfaced (after 10-15 minutes), and immediately paralyzed in 1.0 g of Tricane-S dissolved in 1.0 liter of seawater (collection method approved by the Institutional Animal Care and Use Committee [IACUC] at University of Maine, Orono; Beal et al. 2016). Specimens were depurated for 24-48 hours and then stored at -10°C. Samples were freeze-dried prior to isotopic analysis. Algal tissue, muscle tissue from large animals, and the entire soft tissue of small animals were analyzed. Tissue samples weighed between 0.4-0.6 mg, and algal samples between 2.0-2.5 mg. Stable isotope analyses was performed using a Delta V stable isotope ratio mass spectrometer (IRMS) (Costech Elemental Analyzer Model 4010) in the Environmental Geochemistry Laboratory, Bates College, in Lewiston, Maine. Stable isotopes were expressed in the δ notation.Individual wrymouth were weighed to the nearest 0.1 g, and total length measured to the nearest 0.5 cm. Full and empty stomachs were weighed, and the difference was used to calculate the mass of gut contents. Contents were observed under a stereoscopic microscope at 30x and individuals classified to the lowest possible taxonomic level and recorded as present, following methods of Beal et al. (2016). Statistical analysis was conducted in R.