title: Local site differences in survival and parasitism of periwinkles (Littorina sitkanaPhilippi, 1846).
abstract: The periwinkle,Littorina sitkana, is found throughout the intertidal zone, often in isolated subpopulations. The majority of trematode parasites use snails as intermediate hosts, and decreased survivorship is often observed in snails infected with trematodes. SamplingL. sitkanafrom four sites in Barkley Sound, British Columbia, Canada, we test the effects of parasitic infection on snail survival using maximum likelihood and Bayesian approaches using the software MARK and WinBUGS. We found that survival of periwinkles and trematode community composition differed among sites, but survival and trematode prevalence were uncorrelated. WinBUGS performed better than MARK in two ways: (1) by allowing the use of information on known mortality, thus preventing survival overestimation; and (2) by giving more stable estimates while testing the effect of body size on snail survival. Our results suggest that snail survival depends heavily on local environmental factors that may vary greatly within a small geographical region. These findings are important because the majority of experimental studies on survival are done on snails from a single location.
authors.affiliation: Bamfield Marine Sciences Centre Bamfield BC Canada; Department of Biology University of Victoria Victoria BC Canada.
authors.forename: Mónica
authors.initials: M
authors.lastname: Ayala-Díaz
authors.affiliation: Bamfield Marine Sciences Centre Bamfield BC Canada.
authors.forename: Jean M L
authors.initials: JM
authors.lastname: Richardson
authors.affiliation: Bamfield Marine Sciences Centre Bamfield BC Canada; Department of Biology University of Victoria Victoria BC Canada.
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Anholt
keywords: Barkley Sound; MARK; Mark‐Release‐Recapture; WinBUGS; parasites; snail ecology