This report from the Canadian Science Advisory Secretariat (Science Advisory Report 2010/030), dated July 2010 finds:
The status and trends of Canadian marine ecozones are changing owing to a suite of different factors.
Biological and ecological effects (e.g. increased natural species mortality, species range expansions and contractions, and changes in fish size, assemblages, and community structure) are occurring; however their impact on ecosystems is not always well understood.
Climate change and oceanographic variability are affecting most Canadian marine ecozones. In particular, ocean acidification is known to be impacting several ecozones and is an emerging issue in the others.
A decline in many fish stocks has occurred on the Atlantic and Pacific coasts as a result of commercial overexploitation. Although management measures have been implemented for most species, recovery has been limited in most cases.
Legacy contaminants, like polychlorinated biphenyl (PCB) and Dichlorodiphenyltrichloroethane (DDT) for example, are decreasing, however the incidence of emerging contaminants (e.g. brominated flame retardants) are becoming an issue in most ecozones.
Industry and development have, or are threatening to, impact most ecosystems. The coastal zone is particularly vulnerable and is of concern as these areas are considered highly productive ecosystems.
Some marine mammals that were overexploited in the past are now recovering. For example: bowhead, beluga, and narwhal in the Arctic, and sea otters, stellar sea lions, harbour seals, killer whales, humpbacks, and gray whales in the Pacific.
Populations of grey seals in the Gulf of Maine and Scotian Shelf ecozone and harp seals in the Newfoundland-Labrador Shelves ecozone have increased dramatically.
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