Marine Ecology Progress Series
MEPS is a leading hybrid research journal on all aspects of marine, coastal and estuarine ecology. Priority is given to outstanding research that advances our ecological understanding.
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DOI: https://doi.org/10.3354/meps15045
copiedThirty-five years of cetaceans in a canyon: patterns, shifts, and surprises in the Gully marine protected area
The Gully, a large submarine canyon on the edge of the Scotian Shelf, was made a marine protected area (MPA) in 2004. Together with 2 neighbouring smaller canyons, it has a particularly high density and diversity of cetaceans. We compiled sightings made from vessels during summer months between 1988 and 2023 to describe temporal and spatial trends of occurrence for 9 commonly sighted cetacean species in the Gully MPA and nearby waters. We looked for correlations between species as well as potential drivers of trends. Sighting rates increased for Sowerby’s beaked whales Mesoplodon biden and long-finned pilot whales Globicephala melas; decreased for humpback whales Megaptera novaeangliae, Atlantic white-sided dolphins Leucopleurus acutus, and striped dolphins Stenella coeruleoalba; while northern bottlenose Hyperoodon ampullatus and fin whales Balaenoptera physalus showed U-shaped trajectories. White-sided dolphins were more abundant in June, when water temperatures are cooler, whereas most of the other species showed a preference for the warmer months. Blue whales Balaenoptera musculus were most abundant with sea temperatures of ~18°C. The northern bottlenose whale is exceptional in that a large portion of the population is in the Gully at any time, there was no seasonal variation in sighting rates, and the inter-annual U-shaped trend can be linked with some confidence to reduced anthropogenic impact following the introduction of the MPA. For the other species, drivers are more speculative but include changes in relative resource abundance due to oceanographic and ecological processes, climate change, and variation in anthropogenic impacts.
KEYWORDS
White-sided dolphin (left) abundance declined in the Gully canyon since 1988, while northern bottlenose whales (right) have increased since 2004.
Photo: David Gaspard
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Hal Whitehead (Corresponding Author)
- Biology Department, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
- Biology Department, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Handling Editor:
Peter Corkeron, Nathan, Queensland, Australia
Reviewers:
D. Claridge and 2 anonymous referees
Acknowledgements:
The northern bottlenose whale project has received funding from the Natural Sciences and Engineering Research Council of Canada, World Wildlife Fund/Canadian Wildlife Service Endangered Species Recovery Fund, the Department of Fisheries and Oceans, the Canadian Wildlife Federation, the Canadian Whale Institute, the Okeanos Foundation, the Whale and Dolphin Conservation Society, and the Canadian Federation of Humane Societies. The data were compiled by Shannon Gowans, Sascha Hooker, Tonya Wimmer, Hilary Moors, Olivia Paitich, L.J.F., Sam Walmsley, and H.W. We also acknowledge the ESA Climate Change Initiative and the SST CCI project for providing the satellite-derived SST data free of charge.