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. R2 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 (R2 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.

What can cetacean stranding records tell us? A study of UK and Irish cetacean diversity over the past 100 years

“…North Atlantic Oscillation (NAO)-In contrast to other studies , Truchon et al 2013, we found only a slight effect of NAO on the number of stranding events in our main model. However, this was so small that it was inconclusive.…”

“…Previously, positive NAO indices have been positively correlated with high stranding frequencies for seasonal migratory cetaceans (such as minke whales) in the Atlantic (Truchon et al . ). Further, incidences of sperm whale strandings in the North Sea are higher during warm periods (associated with the NAO and higher SST), a likely reflection on changes in distribution of their prey (Robinson et al .…”

Sea Turtle Beach Monitoring Program in Brazil

“…The oil and gas industry has long adopted more effective environmental practices and increased awareness with regard to the social and environmental responsibility of its operations. For industrial activities to occur in a sustainable manner, it is fundamental to conduct multidisciplinary studies that furnish reference data on the environment in which such The majority of studies on stranded marine animals are conducted with mammals [48][49][50][51][52] and seabirds [53][54][55][56]. However, researchers have become more engaged in the monitoring of stranded sea turtles in coastal regions throughout the world, including Brazil, which is an effective approach to investigating the ecology and epidemiology of these animals [29,[57][58][59][60][61][62].…”

Insights into processes of population decline using an integrated population model: The case of the St. Lawrence Estuary beluga (Delphinapterus leucas)

“…Although the events that initially triggered this perturbation are not known, the problem seems to have worsened in the last 6 years, following a harmful algal bloom due to Alexandrium tamarense producing a highly toxic saxitoxin which caused high mortality in 2008 (Truchon et al, 2013;Scarratt et al, 2014;Starr et al, Unpublished results). This event seems to have extended the period of low recruitment and resulted in a highly synchronized 2-year reproductive cycle that is characterized by rising newborn mortality.…”