Arxiu d'etiquetes: sea lion

Reasons to watch marine mammals in captivity (or maybe not)

The topic we are discussing this week is marine mammals in captivity, a very controversial subject. While some people totally agree with this practice because they defend that are beneficial (not only economical), others are against it.


In the discussion about marine mammals in captivity; zoos, aquaria and and dolphinaria maintain that their shows have such a great value in conservation, people learn a lot and that marine mammals have a good life. On the contrary, animal protection groups and more and more scientists defend their lives are impoverished, people don’t receive a good information of the species and that captures of wild animals negatively impacts populations and habitats.


Despite in some countries is compulsory to offer educational values in their shows, there is less evidence that the industry spreads information about marine mammals and their habitats. There are more than 1,600 centres in United States and just a negligible part are actually involved in educational and conversational issues, since most of them just aspire to entertain their visitors.

Tricks performed by sea lions, dolphins or whales are exaggerated variations of their natural behaviours and cause the audience loose the notion of the place they are: inside pools confined by Plexiglas. In a survey of 1,000 US citizens, the respondents overwhelmingly preferred to see captive marine mammals expressing natural behaviours rather than performing tricks and stunts.

Killer whale and Sea lion - Daniel BianchettaContrast of the behaviour between a killer whale (Orcinus orca) and a sea lion. In the right, the natural behaviour, which consists on a killer whale capturing a sea lion (Picture: Daniel Bianchetta). In the left, artificial behaviour in which a sea lion gives food to a killer whale.

In general, almost nothing is explained  about natural behaviours, ecology, demographics or population distribution during the shows. In addition, it has been demonstrated that the information is sometimes incorrect of distorted. For example: SeaWorld doesn’t use the word “evolution” as many visitors consider the theory of evolution to be controversial, they fool in the explanation of the drooping fin syndrome in killer whales or about their life span in captivity.

Another example is that many actions performed by dolphins in shows or observed being directed toward visitors or trainers that are portrayed as play or fun (such as the rapid opening and closing of the mouth and the slapping of the water surface with the tail flukes or flippers) are actually displays that in wild animals would usually be considered aggressive.

Tail slapAggressive behaviour of a dolphin, slapping the water surface with the tail flukes(Picture from Sara's Cetacean Stories).

So, the exhibition of marine mammals does exactly the opposite of what the industry rhetoric claims: instead of sensitizing visitors to marine mammals and their habitats, it desensitizes humans to the cruelty inherent in removing these animals from their natural habitats and holding them captive.


Zoos, aquaria and dolphinaria have increasingly promoted themselves as conservation centres, emphasizing their role as Noe ark. In fact, they do no more than produce new individuals of a limited group of species and do not maintain true conservation programs.

While several zoos have programs to breed endangered species in captivity with the intention that these animals be used in restocking depleted populations, this is not the case with dolphins. Only one facility attempted a captive breeding program for baiji or Yangtze river dolphins (Lipotes vexillifer).

Baiji-at-waters-surface-to-breathe-showing-blowholeBaiji or Yangtze river dolphin (Lipotes vexillifer) (Picture: Mark Carwardine, Arkive).

Moreover, the number of centres that invest money in conservation programs are few in number and the amount of money is less that 1% of their benefits. Fewer than 5 to 10 percent of zoos, dolphinaria and aquaria are involved in conservation programs, either in natural habitat (in situ programs) or in captive settings (ex situ).

Nevertheless, in Europe these centres are obliged for law to develop conservation programs to free the animals breeding in captivity to the nature. The truth is that the overwhelming majority of marine mammal species currently being bred in captivity is neither threatened nor endangered. In addition, the success of these programs would be in the capability to introduce the animals in the nature, what has been done in few chances.

What is worse is that many dolphinaria and aquaria are buying animals directly captured in the wild populations.


All cetacean capture methods are invasive, stressful and potentially lethal, despite the method generally considered the better consists on chasing them by small boats and then herded together and encircled by a net. The process is so traumatic that mortality rates shoot up six-fold in the first five days of confinement. The dolphins not selected and released from the net may experience a similar risk of dying once the capture operators have left the area.

japan-environment-dolphinsCapture of dolphins in Japan during a seine-net capture (Picture: Adrian Mylne, Reuters)

The most violent and cruel method of collecting cetaceans for dolphinaria is the drive fishery, used primarily in Taiji and Futo, Japan. A fleet of small ships produce underwater noise with metal pipes to force the dolphins to go into shallow water. Some of the animals are set aside for the public display facilities, while the rest are killed for human and pet food and other products.

Peter Carrette Archive CollectionDolphin slaughter in Taiji (Japan) (Picture: unknown author).


The one area of activity in which dolphinaria and aquaria can legitimately claim to serve a conservation function is work involving rescue, rehabilitation and release of stranded marine mammals. Indeed, there are some very good stranding rehabilitation programs, but the interests are not always clear.

Usually, the real interest is to promote a good reputation of themselves, so they promote themselves as altruists centres that care for marine mammals in the wild. In addition, they use a stranding as proof that marine mammals’ natural habitat is a dangerous place full of human-caused and natural hazards. The public receives a skewed picture in which an animal’s natural environment is hostile and captivity is a benign alternative.

Also disturbing is the fact that these industries appear to evaluate each animal in terms of display potential. Species that are highly desirable or rarely observed in captivity may be determined to be unsuitable for release.


Almost always, dolphinaria and aquaria claim that they foster research and scientific study of marine mammals, thereby contributing to both education and conservation. However, much of what can be learned from captive marine mammals has in fact already been learned (reproductive physiology length of gestation, visual acuity and general physiology). Moreover, most of the results given by studies made on captivity animals have been demonstrated to not be correct, specially those related with behaviour.

There may be some research questions that the study of captive animals can answer most directly, but due to advancements in technology such as biopsy darts, electronic tags and underwater video, as well as improvements in capture and release techniques, it can be studied in wild animals.

sea-lion-metabolic-domeUse of a metabolic dome to study the metabolism of sea lions (Picture from Vancouver Aquarium).


  • Kleiman, D.G.; Thompson, K.V.; & Kirk Baer, C. (2010) Wild Mammals in Captivity. Principles and Tecniques for Zoo Management. The University of Chicago Press (2 ed).
  • Rose, N.A; Parsons, E.C.M & Farinato, R. (2009). The case against Marine Mammals in Captivity. The Humane Society of the United States and the World Society for the Protection of Animals (4 ed)

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The awesomest fish: the sunfish

This week I want to dedicate this post to common sunfish (Mola mola), one of the biggest bony fishes in the planet and the one with the smallest brains compared with its body. Curiously, an individual of 200 kg had a brain of just 4 grammes (like a walnut)! 


Nowadays, there are four species of sunfishes, which are all included in the Molidae family: the Roundtailed or Common mola (Mola mola), the Southern ocean sunfish (Mola ramsayi), the Sharp-tailed mola (Masturus lanceolatus) and the Slender mola (Ranzania laevis). Today, I will talk about the Common mola (Mola mola) because it is the commonest.

Mola mola 1 Roundtailed or Common mola (Mola mola) (Foto:Per-Ola Norman, Creative Commons)
Masturus_lanceolatus2Sharp-tailed mola (Masturus lanceolatus) (Foto: NOAA/PIRO Observer Program, Creative Commons)
Ranzania_laevis2Slender mola (Ranzania laevis) (Foto: NOAA/PIRO Observer Program, Creative Commons)


Common mola’s body have been somehow truncated leaving them little more than a large head with long fins atop and below. Not having in consideration the fins, its body is less than twice as long as it is deep. The tail is not exactly a tail; it consists on expansions of the dorsal and anal fin rays and it is rounded. Skin is gritty and is covered with mucus. Its body is typically silvery in color with slight sheen and can exhibit changeable spotty patterns.

Mola molaCommon mola (Mola mola). Picture made by Blanca Figuerola (Visit her site).

Teeth of each jaw are joined forming an only piece, with an small mouth compared with the body.

The average size for an adult is 1.8 m (from the mouth till the end of the tail) and 2.4 m from each end of the fins. The average weight is one tonne. They hold the record for the world’s heaviest bony fish: a 3.1 meter long specimen weighted in at 2,235 kg.


Sunfishes have a high reproductive potential, as a female of 1.4 meters long can produce 300 million eggs in its single ovary, which are tiny. They have three larvae stages and in the last, the body is covered by bony rays, which are lost when they achieve the adult age.


Common mola eats a variety of foods, being the most common prey items of gelatinous zooplankton like jellyfishes, Portuguese man-o-war, ctenophores and salps. In addition, they feed on squids, sponges, serpent star bits, eel grass, crustaceans, small fishes and eel larvae.


They live in all tempered seas and oceans worldwide. They usually live in open sea, but sometimes they move closer the coast, from the surface to 300-400 m deep.


It has been detected more than 50 species of parasites in sunfishes, from very different groups, including shark larvae. Moreover, it has been found parasites in their parasites.

On the other side, due to its size, they have few predators, just killer whales and sea lions. Sea lions exhibit a behaviour related to sunfishes. They eat their fins and they abandon the body and sinks to the bottom, where are ate by starfishes.


If you find it interesting, we really appreciate that you share this post in the Social Networks to allow more people to read it, so the goal of the blog is the science dissemination.

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Licencia Creative Commons Atribución-NoComercial-CompartirIgual 4.0 Internacional.