“How many whales do we really need? I figure five. One for each ocean.” Denis Leary
For a long time scientists and fisheries have underestimated the role large whales play in a healthy ecosystem. And, the commercial fishermen who complain that whales steal fish from their nets have it completely wrong.
An increase in large whales around the world could lead to more fish and a healthier ocean scientists report in a review study published this month in the journal Frontiers in Ecology and the Environment.
The underestimation of whales occured because ‘when oceanographic studies were started, large whales were largely absent from the ecosystem-because we had killed most of them,’ says Joe Roman the study’s lead author and a biologist at the University of Vermont in Burlington.
Large whales such as blue, right and gray were heavily hunted until the 1970s. At that point an estimated 66 to 90 percent of the animals had been removed from ocean waters. But since then, great whales have been slowly recovering and now there are tens of thousands of grey whales.
But blue whales – the largest animal ever known to have lived on the planet – have been slower to come back, scientist think their absence may have altered the ecosystem in a way that made it harder for all life to survive there.
As whale numbers have increased and technology has become even more advanced scientists have been able to track and tag seafaring animals which has enables them to gain a better understanding of how important cetaceans are.
So why are Whales so Important?
Whales often feed at great depths then return to the surface to breathe, this mixes up the water column and spreads nutrients and microorganisms through different marine zones, this can lead to major feeding bonanzas for other creatures.
Whale deaths can also be very helpful as well, when a massive mammal dies and its body sinks to the bottom of the sea where it then nourishes unique ecosystems of scavengers from hagfishes to worms. Many of these species are not found anywhere else.
‘Because [humans] took out so many whales, there were probably extinctions in the deep sea before we knew those [scavenger] species existed’ says Roman
Maddalena Bearzi a marine biologist, president of the Californian based Ocean Conservation Society and author of Dolphin Confidential calls the paper released by Roman and other scientists ‘a great and interesting piece’.
What the fishermen say
For decades commercial fishermen have complained that whales eat the fish they are trying to catch and even Japan’s government have been complaining going as far as saying that it is necessary to continue whaling as ‘whales are threatening our fisheries’ (for more see Japan’s Commercial Whaling Efforts Should Resume.
One of Japan’s international whaling negotiators Masayuki Komatsu said that ‘there are too many’ Minke whales and even called them ‘the cockroach of the ocean’.
We know now that it is more complex than this, and for the time being the next step will be to conduct more studies on the complex processes that could help scientists understand exactly how plankton and other organisms respond to the presence of whales.