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Eng Course- Humpback Whales- Download Free PDF

Humpback whales are common in feeding areas off British Columbia (BC) from spring to fall, and are
widely distributed along the coast. Climate change and the increase in population size of North Pacific
humpback whales may lead to increased anthropogenic impact and require a better understanding of
species–habitat relationships. We investigated the distribution and relative abundance of humpback
whales in relation to environmental variables and processes in BC waters using GIS and generalized
additive models (GAMs). Six non-systematic cetacean surveys were conducted between 2004 and 2006.
Whale encounter rates and environmental variables (oceanographic and remote sensing data) were
recorded along transects divided into 4 km segments. A combined 3-year model and individual year
models (two surveys each) were fitted with the mgcv R package. Model selection was based primarily
on GCV scores. The explained deviance of our models ranged from 39% for the 3-year model to 76% for
the 2004 model. Humpback whales were strongly associated with latitude and bathymetric features,
including depth, slope and distance to the 100-m isobath. Distance to sea-surface-temperature fronts
and salinity (climatology) were also constantly selected by the models. The shapes of smooth functions
estimated for variables based on chlorophyll concentration or net primary productivity with different
temporal resolutions and time lags were not consistent, even though higher numbers of whales seemed
to be associated with higher primary productivity for some models. These and other selected
explanatory variables may reflect areas of higher biological productivity that favor top predators. Our
study confirms the presence of at least three important regions for humpback whales along the BC
coast: south Dixon Entrance, middle and southwestern Hecate Strait and the area between La Perouse
Bank and the southern edge of Juan de Fuca Canyon.


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