Ecological Archives E088-053-A2

Julie C. Ellis, Myra J. Shulman, Megan Wood, Jon D. Witman, and Sara Lozyniak. 2007. Regulation of intertidal food webs by avian predators on New England rocky shores. Ecology 88:853–863.

Appendix B. Estimates of tidal migration by Cancer borealis: additional methods.

Snail Tethering Experiment: L. littorea were glued (Loctite Superglue Gel) to the frayed end of a 10-cm nylon line which was attached to a ring cemented to a brick. Five tethered snails were picked randomly and then tied to a single brick and five bricks were placed in the low Chondrus zone at each study site. Each snail was checked daily for 12 days and the condition of tether, shell, and animal recorded. Previous experiments with this technique have shown very low tether failure (Perez et al., unpublished data); additionally, tether failures and artifacts are likely to be similar across the six study sites. Algal Censuses: Each quadrat was divided into twelve 17 × 17cm squares; in eight randomly determined squares, the percent cover of each alga was visually estimated by two observers, a method previously shown to provide accurate results (Dethier et al. 1993).


Dethier M. N , Graham E. S, Cohen S, and L. M. Tear. 1993. Visual versus random-point percent cover estimations - objective is not always better. Marine Ecology Progress Series 96:93–100.

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