Mediterranean Fin Whale Numbers Were Overestimated
July 29, 2012

Mediterranean Fin Whales In More Trouble Than Previously Believed

Brett Smith for - Your Universe Online

The fin whale, like many other whales, was decimated by whaling throughout the 19th and 20th century – to the point of being considered officially endangered and being placed on the IUCN Red List.

This status is determined primarily by calculating a species population and a new study suggests that scientists may have overestimated the whale´s already diminished numbers in the Mediterranean.

For years, it was believed that fin whales in the Strait of Gibraltar and the connecting Alboran Sea accounted for part of the Mediterranean´s total population. However, according to a study published in Marine Mammal Science these whales that cruise the western Mediterranean include some individuals that migrate in from the Atlantic.

"The Mediterranean population has easily been overestimated, as the census included the whole of the southeast Mediterranean, incorporating Atlantic fin whales within the Mediterranean census", said lead author Manuel Castellote, a researcher in the National Oceanic and Atmospheric Administration (NOAA) in Seattle.

The research team analyzed almost 30,000 hours of audio recordings made of fin whale songs to identify both the Mediterranean fin whales and north Atlantic fin whales in the Straits of Gibraltar, where the two populations share a common stomping ground.

Results culled from the recordings reveal that the areas of the Straits of Gibraltar and the Alboran Sea, are exclusively the domain of Atlantic fin whales that visit the Mediterranean Sea in the spring and autumn.

As an unfortunate consequence, "the population of Mediterranean fin whales presents a much more limited distribution than currently described, excluding a significant region of the western Mediterranean,” Castellote said.

The study also pointed out another ℠threat´ facing fin whales and other threatened species – inaccurate population and behavior information. Castellote stressed that gaps in accurate knowledge can not only be embarrassing, it can also serve to undermine conservation strategies that might be implemented.

In addition to determining population statistics, the researchers also recorded a considerable displacement of fin whales, which was prompted by the noise from geophysical prospecting at a distance of over 170 miles from the research area. Researchers noted that undersea noise could disrupt whale communication, unnecessarily waste valuable energy, and reduce the reproductive rates.

"The noise generated through human activity in the oceans leads to possible chronic effects on the health of this species,” Castellote said.

Besides noise pollution, fin whales are particularly prone to collisions with merchant ships and ferries, a major cause of fin whale mortality.

Last month, a fin whale washed up on the California coast after being struck by a ship. This incident along with increased whale sightings near the coast caused the Coast Guard to issue a warning to large ships urging them to "keep a sharp lookout" for whales in their path. Ships were also directed to keep their speed to 10 knots (11.5 mph) as they cross a threshold into waters where the whales have been sighted.

Fins whales are lured to the California coast by an abundance of krill, their seafood of choice.

Image 2 (below): This is a fin whale which appeared stranded on the beach in Marbella (Spain) in 2008, the skeleton of which is on display in the National Museum of Natural Sciences in Madrid. Credit: Rjime31