where are these type of whales mostly found?
Monterey Bay, San Diego, Baja California Sur, Mexico; Gulf of St. Lawrence to name some.
Blue whale
In the North Pacific, blue whales can be seen in large numbers in Monterey Bay, CA from July through October. They may also be seen off San Diego, CA in July and August, and off Baja California Sur, Mexico and in the Sea of Cortez from January through March. In the North Atlantic, blue whales can be seen in the Gulf of St. Lawrence June through September, especially in the Saguenay–St. Lawrence Marine Park in Canada. 
how long does it take for a blue whale to give birth Gestation lasts 10–11 months.
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Blue whale [SEP] Locations and dates
In the North Pacific, blue whales can be seen in large numbers in Monterey Bay, CA from July through October. They may also be seen off San Diego, CA in July and August, and off Baja California Sur, Mexico and in the Sea of Cortez from January through March. In the North Atlantic, blue whales can be seen in the Gulf of St. Lawrence June through September, especially in the Saguenay–St. Lawrence Marine Park in Canada. Blue whales can best be found off Reykjavík and Húsavík in Iceland from May to August. Around the Azores, the best chance to see blue whales is February to March.