Arxiu de la categoria: Marine mammals: Human effects and interactions

Cetaceans and fishing: a dangerous relationship

The cetaceans are creatures that live in the seas and oceans of the Earth. Like other animals, not only must they cope with natural threats to their environment, such as predation or disease, but they also interact with human activities, such as fishing. Here we will see how fishing threatens the populations of these marine mammals. 

CETACEANS AND FISHING: A DANGEROUS RELATIONSHIP

According to a recently report published by Ecologists in Action, the main threats of anthropic origin that cetaceans have to overcome are fishing, aquaculture, submarine noise, collisions with boats, marine litter, chemical pollution, sighting tourism , research, climate change and dolphinariums.

amenazas cetaceos
Cetaceans have to face several anthropic threats and they might beach at coast (Picture: Bahnfrend, Creative Commons)

WHALING

During the last century, whaling activity captured more than three million individuals worldwide, especially in the southern hemisphere, where according to the IWC, about 750,000 individuals of fin whales (Balaenoptera physalus) and 400,000 specimens of sperm whales (Physeter macrocephalus) were captured, among others.

It is known that until the 1960s, hundreds of thousands of blue whales were captured, the largest animal that inhabits the Earth. Despite conservation efforts, currently only between 10,000 and 20,000 individuals survive, a small part compared to those that inhabited the Earth before the boom in the whaling industry.

industria ballenera, relacion cetáceos pesca
Picture showing whaling (Picture: Creative Commons)

In fact, according to a study by Tulloch et al. (2017), although there is currently an international moratorium and major conservation efforts are being made, in the year 2100 the populations of cetaceans that were the object of catches will reach, at most, by half of its original size.

Contrary to the prohibitions established in 1986, there are countries that continue to catch whales and dolphins. These countries are mainly Japan, Norway and Iceland. It is believed that they capture some 1,500 whales annually together, although the demand for meat from these marine mammals is low. In fact, since the ban, it is estimated that some 30,000 whales have been captured.

In Spain, the capture of cetaceans is also prohibited, although it is believed that there is a small illegal activity.

BYCATCH OF CETACEANS

We must bear in mind the impact of accidental catches, one of the main causes of mortality in cetaceans. It consists in the capture of species that are not the target of fishing.

Bycatch can cause a conservation problem when there are endangered species affected, such as the vaquita (Phocoena sinus), a critically endangered porpoise (there are only about 30 animals left around the world), according to the IUCN. mainly due to gillnets.

Bycatch is one of the main causes of mortality, although at European level some measures have been taken, such as Regulation 812/2004. Accidental capture with the use of driftnets was especially important, but this practice is currently prohibited throughout the Mediterranean. In any case, other fishing gears, such as gillnets, purse seines or trawls, are particularly harmful.

In the 1960s, the tuna purse seine fishery in the Eastern Pacific had a significant impact on dolphin populations. The reason is that the fishermen knew that under the groups of dolphins that swam on the surface there are schools of tuna that followed them to take directionality. Thus, knowing this relationship, they surrounded the cetaceans (and therefore the tuna) with the purse seines, killing the former. It is estimated that in 1986 alone, about 133,000 dolphins were captured. To stop this situation, the pressure of the society was fundamental to take the appropriate measures. In fact, currently less than 0.1% of individuals are captured.

relacion pesca cetáceos, pesca accidental delfines
Fishers related dolphins with tuna, so that purse seine affected them (Picture: Wally Gobetz, Creative Commons)

Now we will focus on a case of gillnets. Gillnets kill many different species of cetaceans, both dolphins and whales. Although whales often survive, they often have traces of fishing gear attached to the body, such as nets. Small cetaceans do not suffer the same fate and often die. We have already seen the case of the vaquita , but another porpoise, the harbour porpoise (Phocoena phocoena) is the cetacean that suffers most deaths from gillnets.

Finally, we will see the relationship between cetaceans and trawling. Many species of cetaceans, both dolphins and small whales, feed on the target species of trawling, so they are caught while they are feeding on their prey. In fact, 16 cetacean species have been reported worldwide that feed in association with trawling. The catches are much greater when nets are left at a medium depth than when fishing is done on the seabed.

Despite all conservation efforts, according to an estimate by Read and collaborators, about 300,000 marine mammals are accidentally caught around the world each year due to fishing operations.

COMPETITION FOR FOOD

Finally, we cannot forget that cetaceans and fishermen compete for the same resources. Therefore, we must bear in mind that some cetaceans also interact with fishing to get food. Sperm whales, bottlenose dolphins and killer whales have learned to “steal” food from fishermen.

In fact, they take captures from longline, gillnets and trawl nets, running the risk of being trapped.

In any case, some measures have been taken, such as installing devices that emit annoying sounds for animals. Despite the attempts, they have adapted to it and, in fact, in some cases interpret them as an indication of the presence of fishermen in the area.

REFERENCES

  • López López, L (2017). Cetáceos: los mamíferos más salaos. Informe sobre las interacciones entre cetáceos y actividades humanas. Ecologistas en acción.
  • Hall, MA; Alverson, DL & Metuzals, KI (2000). Bycatch: Problems and solutions. Marine Pollution Bulletin Vol. 41, N 1-6, pp. 204-219.
  • Northridge, S (2009). Bycatch. In Perrin, WF; Würsig, B & Thewissen, JGM (Eds). Encyclopedia of Marine Mammals (pp.167-169). Academic Press (2 ed).
  • Whale and Dolphin Conservation: Stop Whaling
  • World Wildlife Foundation: The Vaquita
  • Cover picture: Omar Vidal (source)

Anuncis

The dugong

Maybe, cetaceans (dolphins, whales and other species) are among the most well-known marine mammals, but other groups are also included: the polar bear, the pinnipeds (which contain walrus and seals), sea otters and sirenians (with manatees and the dugong). In this post, we are talking about the dugong, one of the four living sirenian species. 

INTRODUCTION

Sirenians, also known as sea cows, are an order of four living species, which contain 3 species of manatees (Trichechus) and the dugong (Dugong). The order originated 50-55 million years ago in the African or European region, depending on the sources. All their activities, also the fact of giving birth, take place in the water, so they are totally aquatic mammals. The four species live in warm waters with abundant seagrass and vegetation, since they are herbivorous. Until 18th century, a fifth species existed: the Steller’s sea cow (Hydrodamalis gigas), that was 9 metres long and was hunted to extinction.

Steller's sea cow (Hydrodamalis gigas) (Picture: Encylopaedia Britannica).
Steller’s sea cow (Hydrodamalis gigas) (Picture: Encylopaedia Britannica).

THE DUGONG: DESCRIPTION AND BIOLOGY

Despite nowadays there is a single extant species of dugong, 19 extinct genera have been described by scientists.

Dugongs (Dugong dugon) are sirenians with a gray and smooth skin, the mouth opens ventrally beneath a muzzle and present a dolphin-like tail, which is different from manatees and allows its identification. Due to its strongly downturned snout, dugongs are obligate bottom feeders. Males have tusks, but not females. The flippers are short and lack nails. They may weigh 400 kg and measure up to 3.5 m in length.

Dugong (Dugong dugong) (Picture: WWF).
Dugong (Dugong dugong) (Picture: WWF).

Dugongs inhabit in the tropical and subtropical region of the Indo-Pacific, including Red Sea; in shallow water less than 10 m deep. This represents a potential area of occupancy of more than 125,000 square km. They feed on seagrass rhizomes (more than on leaves) and other plants, which are rich in available nutrients (such as nitrogen) and starch, are easily masticated and poor in fiber. In some cases, they eat invertebrates mainly during the winter at the higher latitudes of their range.

Dugong distribution (Picture: Dugongs Endangered).
Dugong distribution (Picture: Dugongs Endangered).

They are quite difficult to observe because they surface very discreetly, with only their nostrils out of the water. Different from manatees, dugong spends all its life in the sea.

Dugongs are generally solitaries, since the only long-lasting social unit is between the mother and her calf. Females usually have their first calf when they are 6 to 17 years old and the time between births ranges from 3 to 7 years. The usual litter size is one and the gestation period lasts for 13 months. The oldest dugong found in a research was estimated to be 73 years old.

CONSERVATION STATUS AND THREATS

According to the IUCN Red List, dugongs are classified as a vulnerable species. Moreover, the total population size is unknown. Dugongs are vulnerable to several anthropogenic influences:

  • Habitat loss and degradation: the sensitivity of seagrass ecosystems is high and may be destroyed by mining, trawling, dredging, inland and coastal clearing and boat propellers, among others; which reduce the light intensity and, therefore, the growth of these plants.
  • Fishing pressure: the accidental entangling in gill nets, mesh nets and traps, both in the artisanal fisheries and in the industrial scale, is a major threat.
  • Indigenous use and hunting: dugong products are used in most of the countries with available information. These products include meat, leather, oil, medicaments, amulets and other. Fortunately, in many countires, dugong hunting is banned.
Dugongs hunted by the indigenous people of Australia (Picture: Earthrace Conservation).
Dugongs hunted by the indigenous people of Australia (Picture: Earthrace Conservation).
  • Acoustic pollution: there are just few reports of the impact of boat traffic in dugongs, but some suggest a ceasing to use areas with high traffic. Other studies with military detonations suggest potential indirect effects to dugongs such as injury, social disturbance, habitat damage and displacement. Moreover, effects of marine seismic surveys on dugongs might include: interference with their natural communication signals, damage in their ears and behavioural changes.
  • Chemical pollutants: dugongs accumulate high levels of heavy metals, but there is no evidence to be harmful to them; and pesticides.
  • Diseases: dugongs are susceptible to infectious and parasitic disease, like those produced by helminths, protozoans and other parasites.

REFERENCES

Difusió-anglès

Cetaceans have a negative response to summer maritime traffic in Westeran Mediterranean Sea

A team of researchers of several Italian organizations has published on May 2015 its findings about the responses of cetaceans in high sea waters to summer maritime traffic in the Western Mediterranean Sea. This post is a summary of this study. 

INTRODUCTION

Nowadays, cetaceans have to face several threats, like the loss of their habitat, depletion of resources, interaction with fisheries and chemical and acoustic pollution, among others. In the case of ship transport, it can cause long-term changes in distribution, short-term changes in behaviour or direct physical injuries (e. g. collisions).

The Mediterranean Sea is one of the world’s busiest waterways. Moreover, shipping traffic is growing together with the concern of its impacts on fauna. In addition, we have to have in consideration that summer month are the busiest in naval traffic, especially due to the increase on cruise ships and passenger ferries.

The goal of this study was to outcome if the intensity of traffic in high sea waters was statistically different between presence and absence of cetacean sightings.

STUDY AREA AND DATA COLLECTION

Because of most of the Mediterranean cetaceans are mainly pelagic and there is a lack of information in these areas, the research had been conducted along six transects within shipping routes that connects Italy, France and Spain in high sea waters (placed in Ligurian-Provençal basin, the northern and central Tyrrhenian Sea and the Sardinian and Balearic Seas).

Mediterranean Sea basin (Picture from Encylopaedia Britannica)
Mediterranean Sea basin (Picture from Encylopaedia Britannica)

The transects were surveyed from June to September between 2009 and 2013 using ferries as observation platforms. During this period, more than 95,000 km were surveyed and the presence of eight cetacean species was recorded.

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CETACEANS AND MARITIME TRAFFIC

In locations with cetacean sightings, the number of vessels was 20% lower than the number of vessels in the absence of sightings. In the case of the three most frequently sighted species; fin whale (Balaenoptera physalus), striped dolphin (Stenella coeruleoalba) and sperm whale (Physeter macrocephalus); this difference was, respectively, 18%, 20% and 2%. Concerning other species, in the case of Cuvier’s beaked whale (Ziphius cavirostris) the difference was 29% and in the Risso’s dolphin (Grampus griseus) was 43%. It was found that for bottlenose dolphins (Tursiops truncatus) the difference was insignificant. Finally, for common dolphin (Delphinus delphis) and for pilot whale (Globicephala melas) any conclusion can be given.

Nevertheless, despite the number of ships recorded during cetacean sightings was lower in all areas, the percentage difference range from 11 to 49% among areas.

So, in high sea areas during summer, where cetaceans were seen, there were a significantly lower abundance of ships. Some explanations can be given: animals could tend to avoid more impacted zones with small displacements by seeking areas with fewer vessels, could change their distribution to occupy low traffic areas or could increase diving activity where intense traffic occurs. The intensity of the response of cetaceans to the intensity of traffic has important differences among areas and species. So, there are several factors that affects this percentage difference, like specific ecological needs and local environmental conditions. 

In the case of fin whale, where marine traffic is intense, the presence of fin whales is generally lower, with the exception occurring in the central part of the Ligurian Sea. The explanation could be that this region is ecologically favourable in summer since it is a feeding ground for this species and these whales are present for feeding reasons. Therefore, there is a coexistence between traffic and fin whales.

Fin whale (Balaenoptera physalus) (Picture from Circe)
Fin whale (Balaenoptera physalus) (Picture from Circe)

Another example is striped dolphin. Due to its high mobility, this dolphin can avoid the presence of vessels and this could be the reason why there is a negative response between this species and ship presence.

Striped dolphin (Stenella coeruleoalba) (Picture from Marc Arenas Camps)
Striped dolphin (Stenella coeruleoalba) (Picture from Marc Arenas Camps)

About sperm whale and Cuvier’s beaked whale, there were no difference in both species in the Ligurian Sea and the reason probably is that sperm and Cuvier’s beaked whale have their feeding grounds in this basin and, moreover, the slopes and submarine canyons are confined in specific areas. However, differences are observed in other areas.

Sperm whale (Physeter macrocephalus) (Picture from Gabriel Barathieu).
Sperm whale (Physeter macrocephalus) (Picture: Gabriel Barathieu, Creative Commons).
Cuvier's beaked whale (Ziphius cavirostris) (Picture: Todd Pusser, Arkive).
Cuvier’s beaked whale (Ziphius cavirostris) (Picture: Todd Pusser, Arkive).

Finally, bottlenose dolphin did not show any response to traffic. Probably, because it is a coastal species, it is more used to sharing its typical habitat with maritime traffic.

Bottlenose dolphin (Tursiops truncatus) (Picture: Brandon Cole).
Bottlenose dolphin (Tursiops truncatus) (Picture: Brandon Cole).

REFERENCES

This post has been based on this paper:

  • Campana, I; Crosti, R; Angeletti, D; Carosso, L, David, L; Di-Méglio, N; Moulins, A; Rosso, M; Tepsich, P & Arcangeli, A (2015). Cetacean response to summer maritime traffic in the Western Mediterranean Sea. Marine Environmental Research, 109, 1-8

Difusió-anglès

Mediterranean Monk Seal: Until when will it survive?

In this post, we will do an approach to Mediterranean Monk Seal (Monachus monachus), a critically endangered species that, in fact, is the most endangered pinniped species in the world. Here, we are going to do a short historical review and we are going to talk about its natural history, its habitat and distribution, its threats and status and, finally, its conservation. 

INTRODUCTION

Mediterranean Monk Seal (Monachus monachus) is one of the three species included in the genus Monachus (Monk Seals). The other two species are Hawaiian Monk Seal (Monachus schauinslandi), which is critically endangered, and Caribbean Monk Seal (Monachus tropicalis), which is extinct.

mediterranean monk seal, monachus monachus
Mediterranean Monk Seal (Monachus monachus) (Photo: Sá, Wild Wonders of Europe)

Mediterranean Monk Seals were hunted for fur, oil and meat since Prehistory. Romans were responsible of an important decline, but thanks to the empire’ fall the animals were able to recover. More recently, the two world wars, the industrial revolution, the explosion of tourism and industrial fishing have produced the reduction and disappearance of the species in some regions.

MEDITERRANEAN MONK SEAL’S NATURAL HISTORY

When they are born, their length is 94 cm and their weight is 15-20 kg. Until weaning (at about 16-17 weeks), growth takes place fast. The pups’ pelt is soft and downy and the coat is black to dark brown, with a white patch in the belly.

Adult individuals have a length of 2.4 m (from nose to tail) and weigh 250-300 kg. Males are only slightly bigger than females. Juveniles and adults have very short hair. While adult males are black with a white patch in the belly, adult females are brown and grey with a lighter belly colouration. In any case, they can present more patches on the throat (males) and back (females).

Female individual of Mediterranean Monk Seal (Photo: Sá,
Female individual of Mediterranean Monk Seal (Photo: Sá, Wild Wonders of Europe)
Male individual of Mediterranean Monk Seal (Photo: Sá,
Male individual of Mediterranean Monk Seal (Photo: Sá, Wild Wonders of Europe)

Males and females reach sexual maturity between 5 and 6 years. After a gestation lasting 9-11 month, one pup is born (generally in autumn).

They feed on fish and cephalopods.

HABITAT AND DISTRIBUTION

This species’ habitat is inaccessible caves with underwater entrances. The truth is that in ancient times, they inhabit open beaches of sand and rocks. Mediterranean monk seals can be found in warm temperate, subtropical and tropical waters of the Mediterranean Sea and the east Atlantic Ocean.

Mediterranean Monk Seal habitat
Mediterranean Monk Seal habitat (Photo: Sá, Wild Wonders of Europe)
Mediterranean Monk Seal on beach
Mediterranean Monk Seal on beach (Photo: Hellio & Van Ingen)

In ancient times, the species’ distribution was bigger than now. While now they just are present only in the northeast Mediterranean and in the northeast Atlantic, long ago they were present in all through the Mediterranean Sea, Black Sea, Atlantic coast of Africa and some Atlantic islands.

Distribution map of Mediterranean Monk Seal (Monachus monachus) (Picture: TheAnimalFiles.com)
Distribution map of Mediterranean Monk Seal (Monachus monachus) (Picture: TheAnimalFiles.com)

STATUS AND THREATS

With just 350-450 individuals (maybe 550), the Mediterranean Monk Seal is one of the world’s most endangered marine mammals and is the most endangered pinniped species and it is described as critically endangered by IUCN.

Mediterranean Monk Seal is critically endangered, according to IUCN (Picture: IUCN).
Mediterranean Monk Seal is critically endangered, according to IUCN (Picture: IUCN).

The main threats against the species are:

  • Habitat degeneration and loss by development in the coast. The driving causes to this may be hunting, mass tourism, pleasure boats and diving. The result is that the caves occupied now are not adequate for their survival, so the recovery is only possible if they return to sandy beaches.
  • Killing them on purpose by fisherman and fish farm operators because they find it a nuisance that destroys their nets and steals their fish. In Greece, deliberate killing accounts for 43% of the deaths of adult and juvenile animals.
Deliberate killing of a Mediterranean Monk Seal (Monachus monachus) (Picture: A. Karamanlidis, MOm).
Deliberate killing of a Mediterranean Monk Seal (Monachus monachus) (Picture: E. Tounta, MOm).
  • Accidental entanglement in fishing gear. It is unknown if this has an important impact nowadays, but in the recent past it was and, in fact, it has played a significant role in the elimination of the species from some parts.
  • Decreased food availability due to overfishing. Malnourishment; susceptibility towards pathogens; affected growth, reproduction, juvenile survival and mortality rate and dispersion are the possible effects of this.
  • Unusual events: disease (like morbillivirus), toxic algae, rockslides, cave collapses or oil spills.
  • Pollution, maybe caused by organochlorine compounds used in pesticides.
  • Inbreeding depression, that results in reduced fecundity and pup survival. This factor is not a significant threat in the short term, but it can be a future threat because this causes reduced fertility, increased infant mortality and a distorted sex ratio.

CONSERVATION

Since 1970s, conservation measures have been developed, but the improvements are hardly seen. Conservation measures include:

  • Development of marine protected areas (MPA) in Madeira, Greece, Turkey and Cabo Blanco. In fact, what is necessary is a network of MPA.
  • Orphaned and hurt animals are rescued.
  • Educational programs.
  • Scientific investigation to identify its habitat areas.
  • International coordination of conservation activities.

On the other hand, ex situ conservation measures (like captive breeding and translocation) are not used because the species is so sensitive to human disturbance that it could be another threat.

REFERENCES

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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.

INTRODUCTION

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.

CAPTIVITY OF MARINE MAMMALS IS EDUCATIONAL (OR MAYBE NOT!)

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 HELP TO THE CONSERVATION OF SPECIES (OR MAYBE NOT)

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.

CAPTURE OF WILD ORGANISMS

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).

ZOOS, AQUARIA AND DOLPHINARIA HAVE PROGRAMS TO HELP STRANDED ANIMALS (OR MAYBE NOT)

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.

MARINE MAMMALS IN CAPTIVITY ALLOW RESEARCH (OR MAYBE NOT)

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).

REFERENCES

  • 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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