OBRA MAESTRA

KILLER WHALES REPRODUCTION

Genetic Diversity By Maryline Bomane

Killers whales or orca (Orcinus orca) are the top predators of the oceans. They have colonized all the world’s oceans and seas.

The king of the oceans causes much interest.

Indeed, Keiko’s rehabilitation (the most famous captive orca who starred in Free Willy movies) is one of many examples. There was such a craze that  since then the number of orcas in marine zoos has steadily increased.

Unfortunately for killers whales, this new industry has caused their plight. It’s true that this impressive animal is sweet and affectionate in captivity. His intelligence and taste for games makes him even more interesting. Also we must recognize that this specie has a rare intelligence and extraordinary physical strength.

While their power has made them the king of the seas, they remain ruthless killers of the oceans. Also compared to other cetaceans we can’t deny some of the surprising features of orcas regarding their social, lifestyle and behavior. (Guinet, 2004).

It was Mike Bigg and his colleagues who made the first field study on Orcas.

Following their passion was a difficult task, as they had to assess the impact of killer whale catches on wild populations on the Pacific coastlines, British Columbia and the state of  Washington.

« Photo-identification » was born following Big’s observations and photos of killer whales in the Strait of Johnston.

Then John Ford was involved in Orca acoustic communication during his PhD research…being very special because it is a true dialect.

This was the beginning of the wonderfull study of the most fascinating cetacean in the world.

Killer whales have surprising characteristics, having a different mating behavior than most other cetaceans who mate at random. ( Hulot, 2000) (Hulot, 2000)

Acknowledgments

I want to thank Mr Christophe Guinet, researcher at CNRS (CEBC), for his priceless assistance.

Dr John Ford and Dr. L. Barrett-Lennard, for their publications.

And Mr E. Faure, researcher and teacher at University of Provence, Marseilles.

Circe and The Marine Mammal Center for their excellent website & documentations

Learn more about  “la reproduction des orques”…

En effet le programme de réhabilitation de Keiko (orque), acteur fétiche du film ” Sauvez Willy ” est un des nombreux exemples. Il y a eu un tel engouement que depuis le nombre d’orques dans les zoo marins n’a cessé d’augmenter.

Malheureusement pour eux cette nouvelle industrie a fait leur malheur. Il est vrai que cet animal si imposant qu’il soit, est néanmoins doux et affectueux en captivité. Son intelligence et son goût pour les jeux ne le rendent que plus intéressant. Aussi reconnaît-on à cette espèce une rare intelligence et une force physique extraordinaire.

Bien que sa puissance fait de lui le roi des mers, il n’en demeure pas moins un tueur sans pitié en liberté. Par ailleurs comparativement à d’autres cétacés on ne peut pas nier certaines caractéristiques surprenantes  chez les orques en ce qui concerne leur organisation sociale, leur mode de vie et leur comportement.(Guinet, 2004).

Ce fut Mike Bigg et ses collègues qui firent les premières études de terrain sur les orques. Ils eurent la difficile tâche en suivant leur passion  d’évaluer l’impact des captures d’orques sur les populations sauvages des côtes pacifiques de Colombie britannique et de l’état de Washington.

C’est suite à ses observations et aux photographies d’orques dans le Détroit de Johnston qu’est née la technique de la photo-identification.

Puis John Ford se lança dans un programme de thèse sur la communication acoustique des orques qui est très particulière puisqu’il s’agit un véritable dialecte.

C’est ainsi que commença l’étude fabuleuse du cétacé le plus fascinant au monde. L’orque possède ainsi des caractéristiques surprenantes, notamment un comportement reproductif différent de la plupart des autres cétacés qui s’accouplent de manière aléatoire. ( Hulot, 2000)

Remerciements

Je tiens à remercier Mr Christophe Guinet, chercheur au CNRS (CEBC), pour son aide précieuse

Dr John Ford et Dr L. Barrett-Lennard, pour leurs publications.

Ainsi que Mr E. Faure, chercheur enseignant à la Faculté des Sciences de St Charles, Marseille.

Et les sites Circé et The Marine Mammal Center, pour leur excellent contenu qui m’a beaucoup aidé dans mes recherches.

Apprenez plus sur  “la reproduction des orques”…

au COM ( Centre Oceanologie Marseille)

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An international team of researchers has combed through old ships’ logs, tax accounts, ancient texts and other records to reconstruct the vast number of whales, fish and other sea creatures that once swam in the earth’s oceans.

Their work, to be presented at a conference in Vancouver this week, offers an unprecedented global overview of the once astonishing abundance of fish and marine mammals, 10 times more than can be found beneath the waves today.

A text written in Sicily in 1153 describes the seas of the North Atlantic as having “animals of such great size that the inhabitants of the islands use their bones and vertebrae in place of wood to build houses.

They make hammers, arrows, spears, knives, seats, steps and in general every sort of thing elsewhere made of wood.” In Britain, manuscripts from the 17th and 18th centuries and harbour statistics show that large pods of blue whales and orcas, blue sharks and thresher sharks darkened the waters off Cornwall, England, and that herds of harbour porpoise chased fish upriver.

Today, there are 85 to 90 per cent fewer fish and marine mammals than there once were, said Poul Holm, professor of environmental history at Trinity College Dublin and the global chair of the History of Marine Animal Populations project.

“We can now confirm this is a global picture, fairly consistent in the developed and developing world,” he said. He is chairing a conference in Vancouver this week where paleontologists, archeologists, historians, ecologists and other researchers will present their individual findings and start to synthesize them for a report that will be published next year.

They are working on the historical component of the international Census of Marine Life, an ambitious project to track the life forms that inhabit the oceans today that involves 2,000 researchers from more than 80 countries, including Canada.

The researchers used a number of novel approaches to learn about the past. Loren McClenacha of the Scripps Institution of Oceanography in California compared photos of groups of trophy fish landed by sports fishermen in the Key West area of Florida between 1956 and 2007.

The average fish size dropped by almost 90 per cent, from 20 kilograms to 2.3 kilograms. Others looked further back in time, and found that dramatic losses hit much earlier than previously known. People began having an impact on marine life in the Middle Stone Age – 300,000 to 30,000 years ago. Large freshwater fish began to disappear in medieval times, and people headed to sea in search of food.

The shift from eating locally caught freshwater fish to marine species occurred around 1000 AD, probably because of increased exploitation and pollution, researchers from Britain and Germany found. In the Baltics, there was a dramatic increase in the consumption of exotic fish in the 1680s due to rising standards of living and trade outside the region, said Dr. Holm. “It is a reminder of what is happening today.

We are eating into the biodiversity of the southern hemisphere,” he said. In the early to mid 1800s, overfishing and extreme weather conditions led to the collapse of the European herring fishery. Heike Lotze, a researcher at Dalhousie University in Halifax, said she was struck by how, wherever you look in the world, at whatever period, the story is the same.

“People are trying to get the biggest and yummiest fish.” Right whales, however, were hunted for their oil and baleen, used for corsets and other products. An examination of more than 150 whaling logbooks and other records found that the New Zealand southern right whale numbered between 22,000 and 32,000 in the early 1800s, but that by 1925, only 25 reproductive females were left.

Today there are 1,000 animals. Fishing for herring in Tiuva inlet, Murman coast of the Barents Sea, 1930. Photo from the archives of E.K. Suvorov. Department of Ichthyology and Hydrobiology, Faculty for Biology and Soil Sciences, St. Petersburg State University.

Fishing for herring in Tiuva inlet, Murman coast of the Barents Sea, 1930. Photo from the archives of E.K. Suvorov. Department of Ichthyology and Hydrobiology, Faculty for Biology and Soil Sciences, St. Petersburg State University

There is hope that depleted populations can recover, the researchers say. Sea otters in western North America were once down to as few as 64. Today, there are about 2,000, says Dr. Lotze. Elephant seals off the coast of Baja California were almost hunted to extinction, killed for their blubber, which provided oil.

Today their population is well over 100,000. “In the past, some combination of reduced or banned exploitation, pollution controls or habitat protection, especially of breeding colonies and feeding grounds, propelled recovery,” said Dr. Lotze, who holds a Canada Research Chair in marine renewable resources.

Some species can recover more quickly than others, said Dr. Holm. European herring stocks were knocked off again in the 1970s, but due to a massive conservation effort were rebuilt within a decade, he said.

Other species, such as Atlantic cod, can take much longer to rebuild, he said.

“There are fairly convincing studies that show management helps, and if we make a concerted effort and take the time to do it right there is a good chance fish stocks will be rebuilt,” he said.

“The ocean is a much more resilient system than the land”

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