Humpback whale population is growing in recent years.

BY THE BAY: Humpback whales making comeback

Population on rebound, decades after being nearly wiped out, writes columnist Anne Murray.

Spouts of spray against a blue sky, the arch of a dark back and the flip of giant tail flukes as a humpback whale dives deep into the water: a thrilling sight that is becoming more common in local waters.

Humpback populations are on the rebound, 100 years after they were killed off by the whaling industry. It is a most encouraging sign that nature can heal, if given space and time.

B.C. waters have a very rich diversity of marine mammals, including whales, dolphins, porpoises, seals, sea lions and two species of otter. Their presence as larger members of the food chain ensures that the ecosystem can function.

Sea otters, for example, play a vital role in maintaining west coast kelp forests, by eating sea urchins that otherwise overgraze the plants. In protecting the kelp habitat, otters also allow other animals, such as abalone, starfish and fish to survive.

By playing this keystone role in the food chain, otters make a significant impact on carbon sequestration by kelp forests.

Similarly, transient orcas are predators that feed on seals and porpoises, regulating numbers of these fish-consuming animals. More transients are being seen, and their hunting groups are somewhat larger, reflecting the good foraging opportunities.

Conversely, the resident orca population are endangered, as chinook salmon, their principle food source, have seriously declined.

Humpback whales were once common in local waters. In the early 1900s, steamship whaling using explosive harpoons extirpated humpbacks from the B.C. coast, killing 95 within the Georgia Strait.

No whales were seen for decades.

In the 1990s, a few humpbacks ventured into the Juan de Fuca Strait, and then suddenly from 2003 onwards, more began to arrive each year, as the North Pacific population rebounded.

Humpbacks make long migrations, travelling to cool northern seas in summer to feed on krill and small schooling fish. Females brought their calves into the Salish Sea and these young animals independently returned, once grown to adulthood.

Now, humpbacks are being regularly seen around Vancouver Island and the southern Gulf Islands, and are beginning to make their way into the Georgia Strait. Their impact on the local ecosystem should be positive, as they reclaim their place in the food chain.

Sperm whales, another krill-eater, fertilize the sea with their droppings, significantly increasing phytoplankton and consequently extracting carbon from the atmosphere.

Only time will tell what effect humpbacks will have on local waters.

Anne Murray,  the author of two nature books, writes monthly in the Peace Arch News – www.natureguidesbc.com

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