ARTICLE
Abstract: Long time series of abundance data have advanced ecological understanding. I examined trends in incidental sightings of cetaceans in the Gully and neighbouring submarine canyons on the edge of the Scotian Shelf during summers between 1988 and 2011. There were a total of 2938 h of sighting...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1079.5957 http://whitelab.biology.dal.ca/hw/cjz-2012-0293.pdf |
| Summary: | Abstract: Long time series of abundance data have advanced ecological understanding. I examined trends in incidental sightings of cetaceans in the Gully and neighbouring submarine canyons on the edge of the Scotian Shelf during summers between 1988 and 2011. There were a total of 2938 h of sighting effort in good conditions. I fit Poisson models to the sighting count data, and examined the support for models that included parameters representing monthly variations in abundance, trends over years, and different sighting rates in the different canyons. Sowerby's beaked whales (Mesoplodon bidens (Sowerby, 1804)) were sighted 3.5 times more often in the Shortland and Haldimand canyons, compared with the Gully. For all other species, the best-supported models did not include differential sighting rates between canyons. The sighting rates of four species decreased over the 23 years of the study, while three species increased. Some of these trends may be related to changes in overall population size or variation in food resources, but a remarkable 21%/year increase in Sowerby's beaked whale is perhaps most plausibly explained by a reduction in anthropogenic disturbance. Key words: Cetacea, whales, dolphins, canyon, trends, the Gully, marine protected area, Sowerby's beaked whale, Mesoplodon bidens. Résumé : Les longues séries chronologiques de données d'abondance ont fait avancer la compréhension des systèmes écologiques. J'ai examiné les tendances en matière d'observations fortuites de cétacés dans le Goulet et dans des canyons sous-marins voisins en bordure du Plateau néo-écossais, pour les étés de 1988 à 2011. Les données représentent un total de 2938 h d'effort d'observation dans de bonnes conditions. J'ai ajusté des modèles de Poisson aux données de dénombrement des observations et examiné la concordance aux données de modèles qui intègrent des paramètres reflétant les variations mensuelles d'abondance, les tendances sur plusieurs années et différentes fréquences d'observations dans les différents canyons. Des ... |
|---|