title: Marine mammal strandings and environmental changes: a 15-year study in the St. Lawrence ecosystem.
abstract: Understanding the effects of climatic variability on marine mammals is challenging due to the complexity of ecological interactions. We used general linear models to analyze a 15-year database documenting marine mammal strandings (1994-2008; n = 1,193) and nine environmental parameters known to affect marine mammal survival, from regional (sea ice) to continental scales (North Atlantic Oscillation, NAO). Stranding events were more frequent during summer and fall than other seasons, and have increased since 1994. Poor ice conditions observed during the same period may have affected marine mammals either directly, by modulating the availability of habitat for feeding and breeding activities, or indirectly, through changes in water conditions and marine productivity (krill abundance). For most species (75%, n = 6 species), a low volume of ice was correlated with increasing frequency of stranding events (e.g. R(2)adj = 0.59, hooded seal, Cystophora cristata). This likely led to an increase in seal mortality during the breeding period, but also to increase habitat availability for seasonal migratory cetaceans using ice-free areas during winter. We also detected a high frequency of stranding events for mysticete species (minke whale, Balaenoptera acutorostrata) and resident species (beluga, Delphinapterus leucas), correlated with low krill abundance since 1994. Positive NAO indices were positively correlated with high frequencies of stranding events for resident and seasonal migratory cetaceans, as well as rare species (R(2)adj = 0.53, 0.81 and 0.34, respectively). This contrasts with seal mass stranding numbers, which were negatively correlated with a positive NAO index. In addition, an unusual multiple species mortality event (n = 114, 62% of total annual mortality) in 2008 was caused by a harmful algal bloom. Our findings provide an empirical baseline in understanding marine mammal survival when faced with climatic variability. This is a promising step in integrating stranding records to monitor the consequences of environmental changes in marine ecosystems over long time scales.
authors.affiliation: Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, Rimouski, Québec, Canada. marie-helene_truchon@uqar.qc.ca
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Truchon
authors.forename: Lena
authors.initials: L
authors.lastname: Measures
authors.forename: Vincent
authors.initials: V
authors.lastname: L'Hérault
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Brêthes
authors.forename: Peter S
authors.initials: PS
authors.lastname: Galbraith
authors.forename: Michel
authors.initials: M
authors.lastname: Harvey
authors.forename: Sylvie
authors.initials: S
authors.lastname: Lessard
authors.forename: Michel
authors.initials: M
authors.lastname: Starr
authors.forename: Nicolas
authors.initials: N
authors.lastname: Lecomte
mesh_terms: D000818:Animals; D044822:Biodiversity; D017753:Ecosystem; D005843:Geography; D007053:Ice; D016014:Linear Models; D008322:Mammals / Q000502:physiology*; D011792:Quebec; D012621:Seasons; D012623:Seawater; D013997:Time Factors
chemical_list: D007053:Ice
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