What do baleen whales feed on

Acoustic echosounders work much like the echolocation used by dolphins — a pulse of sound is sent out, the sound reflects off of a surface such as a layer of zooplankton and then returns to the source of the sound. The difference between the sound sent out and the sound received tells you something about how many zooplankton are out there, and what they are doing.

An example of the echosounder data showing diel-vertical migration from one of our gliders is given in the figure above. In order to know how much zooplankton is out there by the difference in sound, the echosounder has to first be calibrated in a big tank.

This is done by hanging a small sphere of known composition underneath the echosounder and recording how much sound reflects off of the sphere.

Your email address will not be published. Baleen whales eat swarms of tiny crustaceans called zooplankton, and they engage in all kinds of tricky tactics to get the biggest mouthful of food for the smallest amount of effort. The Challenge Whales are marine mammals, which means they breathe air. All Together Now! For example, researchers thought that the krill-feeding baleen whales living in the California Current Ecosystem, between British Columbia and Mexico, gobble up about 2.

Having determined how much modern-day whales eat, the team wondered how much whales ate in the past, before industrial whaling severely depleted their numbers. They used whaling industry records to address this question, and focused specifically on Southern Ocean lunge-feeding species, which again nab prey by suddenly charging at them.

An estimated 1. The analysis suggests that, at the start of the 20th century, minke, humpback, fin and blue whales in the Southern Ocean likely consumed about The loss of millions of whales between and likely contributed to the subsequent decline in krill, since the whales' poop once fertilized a major food source for the crustaceans, the authors suggest. And on top of the loss of the whales, climate change likely also drove the decline in krill, he noted.

But by both conserving whale populations and addressing climate change, we could potentially regain some of the lost productivity in these ecosystems. All the components of the system — the whales, krill and phytoplankton — are still there, albeit in smaller numbers.

What the system really needs is a "jump start," Savoca said. Jump-starting the system would involve boosting whale populations through a combination of passive conservation efforts, such as establishing new marine protected areas, and active conservation efforts, such as setting ship speed limits to prevent whales from being struck by boats.

Regulations could also bar fishing boats from working when whales are in the area, to avoid entangling the animals in nets. And of course, in addition to these direct measures, broader efforts to rein in climate change would also help whales recover, Savoca said. In theory, Smetacek said, scientists could jump-start the whale-krill system in another way: By purposefully fertilizing phytoplankton with iron, thus boosting the organisms' growth and, in turn, bolstering krill and whale populations.

Essentially, the iron fertilizer would stand in for the missing whale poop. This idea of seeding the oceans with iron has been raised in the past, as a way to increase the amount of carbon that phytoplankton pull from the atmosphere, Mongabay reported. But the idea remains controversial, in part due to a lack of studies on the potential large-scale ecosystem impacts that such fertilization might trigger.

In February , a stranded Cuvier's beaked whale in Norway was found to have ingested around 30 plastic bags. It is estimated that more than eight million tonnes of plastic ends up in Earth's oceans every year.

Experts are warning that by , there could be more plastic in the water than fish. This man-made material is now found on the sea floor , at the surface, on coastlines and even embedded in Arctic sea ice. Read more about the lives of marine animals and find out how Museum scientists are researching them. Early ancestors of the ocean's biggest animals once walked on land. Follow their extraordinary journey from shore to sea. A series of perfectly-preserved humpback whale foetuses reveal how whales grow before they're born.

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