From one of the answers on the Q&A on Amazon. Don't know of its accuracy.
The Canadian and U.S. sardine canning industry is based on the juvenile North Atlantic herring. The North Atlantic herring is a small saltwater fish that is also known by its scientific name Clupea harengus. These fish travel in huge schools and live in the cold waters of the open ocean ranging from Greenland to North Carolina. North Atlantic herring can reach a size of about 40 cm (17 inches) in length, weigh as much as 0.7 kg (1.5 lbs), and can live as long as 20 years. Herring feed principally on plankton and are found in shallow inshore waters to offshore waters as deep as 200 meters. Herring schools are always in motion and migrate between spawning grounds, feeding grounds, and deep-water wintering