Learn About Conservation of Dolphins

Captivity: Pro and Con

As knowledge of dolphin cognition and sociology has grown, so too have concerns as to the ethics of keeping them in captivity.  There is currently a broad spectrum of attitudes and opinions regarding this matter.  As with any complex issue, there are extreme viewpoints on either side of the subject.  This section will attempt to accurately address the perspectives of both the opponents and the proponents of dolphins in captive environments.

Throughout the world, there are countless animal rights groups campaigning for a variety of objectives ranging from humane treatment of animals, to the all-out abolishment of any contact between humans and animals.  In response to dolphins in captivity, groups vary between those favoring higher standards for the care and handling of marine mammals to those opposing any captive setting.  The rhetoric of the more extreme associations asserts that:

Among the institutions and organizations working with captive dolphins, there is also a wide range of opinion.  For example, some consider captivity acceptable provided the animals in question were either captive-born, or have been rehabilitated from illness or injury and judged unfit for return to the wild. 

As both sides of the captivity issue claim to have the “facts”, their allegations must be studied carefully and objectively.  We will begin with the question of educational value in captive displays. 

Obviously, the dolphin’s natural environment can only be simulated, not duplicated.  Although a few dolphinaria are equipped with some natural features, the vast majority are concrete tanks.  Thus, the opponents’ claim that such exhibits are “unnatural” is correct.  But do such surroundings cause the animals to behave abnormally?

For those facilities large enough to allow for fluid social interaction among the animals, studies have shown the social behavior to be generally consistent with that of their wild counterparts.  Proponents point to successful breeding programs as testimony.  However, animals placed closely together without regard for age, sex, and in some instances -- species, cannot be expected to accurately depict “natural” behavior.  

Fisheries vs. Dolphins

Despite world-wide interest and concern for dolphins, there are still a few countries that maintain active dolphin fisheries.  In some areas, small fishing villages have gained notoriety for corralling and slaughtering dolphins on the grounds that the animals simply eat too many fish.  Even in the United States, where they are protected by federal law, it is not uncommon for a dolphin to wash up on a beach with a bullet hole in its body.  The greatest number of mortalities, however, result from accidental catch due to fishing operations.

Many whales and dolphins are inadvertently killed after tangling in commercial fishing gear.  Drift gillnets, set gillnets, purse seine nets, longlines, and trawls are all involved in accidental death or serious injury for marine mammals. 

Drift gillnets are deployed in deep open waters while set gillnets are used in shallower coastal waters.  Both are made of finely woven monofilament nylon designed to catch fish attempting to swim through the mesh, by snagging the gills and preventing their escape.  Although these nets are intended to catch a few target species of fish, they often entangle a wide variety unwanted fish, sea turtles, and sea birds; in addition to marine mammals such as whales, dolphins, porpoises, seals, and sea lions.  The other fishing techniques such as purse seining, trawling and longlining also lead to occasional entanglement and accidental catch.

Based on the knowledge of dolphin echolocation abilities, there are questions as to why they don’t detect and avoid nets and lines.  One theory for deep water driftnet entanglement, is that dolphins don’t anticipate obscure obstacles such as thin monofilament mesh while traveling through the open sea.  Although they are likely to be projecting low frequency clicks to scan for large objects such as sea mounts, boats, and large marine animals; these same sounds probably don’t reflect well off of thin netting. 

In the case of other nets and lines, some dolphins are known to “steal” the trapped fish off of the fishing gear.  In doing so, a few become accidentally tangled. 

In response to this problem, a number of nations have implemented various plans that include modifying fishing gear, restricting gear use during certain times and in certain areas, and developing fisher education programs, all with the goal of reducing entanglement.  

Habitat Degradation

Perhaps the greatest overall threat facing dolphins today, and in the future,  is the degradation of their natural habitats.  Coastal development, overfishing, pollution and toxic waste are disrupting the natural balance of our waters.  Dolphins are being killed, both directly and indirectly, as a result of man’s impact on the environment.

For the coastal bottlenose dolphin, commercial development along bays, estuaries, and rivers has important ramifications.  The highly productive mangrove forests, saltmarshes, and seagrass meadows host a multitude of plant and animal life.  These areas serve as nurseries for a variety of  fish, many of which the dolphins depend upon for food.  Dredging and filling in wetlands places great stresses on these complex and fragile ecosystems.  In some areas, overdevelopment has resulted in poor water quality and reductions in local fish populations.  Uncontrolled and wasteful fishing practices also disrupt the natural balance of coastal food chains.

Whether through accidental ingestion or entanglement, marine debris is particularly dangerous for dolphins.  Styrofoam, plastic bags, six-pack rings, and discarded fishing line are not biodegradable and accumulate in enormous amounts throughout the world’s oceans. 

Many dolphins suffer death and disease as a result of toxins and wastes dumped into the sea.  Pollutants such as heavy metals and chlorinated hydrocarbons accumulate in the tissues of marine plants and animals.  The higher an animal on the food chain, the higher the concentrations of these chemicals; which severely disrupt biological processes --  resulting in organ failures, cancers, reproductive failure, and immune system suppression.   These substances have been found in extremely high levels in the blubber of dead dolphins washing up on beaches. 

Polychlorinated biphenyls  (PCB's), and the insecticide DDT are considered two of the more troublesome pollutants.  These chemicals not only accumulate in the tissues of plants and animals, they also linger in soils and sediments.  Although the production of PCB's and the use of DDT have been banned in Europe and North America for years, environmental levels in some areas are still high; and there is a continuing low-level input.  There are still many manufactured goods in circulation which contain large quantities of PCB's.  Often products are not properly labeled and releases of these compounds occur when they are disposed of.  PCB's continue to leach into the groundwater through landfills.  DDT is still used in many developing countries, and remains a threat to local marine mammal populations. 

Eating a single contaminated fish does not normally result in immediate problems for a dolphin.  The problem is one of a cumulative effect.  Certain chemicals do not pass readily out of an animal's body, rather, they are stored in fatty deposits.  Those organs rich in fats, such as the adrenals, testes, thyroid, liver, and kidneys are particularly vulnerable.  For the dolphin, the blubber layer is a storehouse for contaminants.  This is of critical importance for an animal undergoing environmental or physiological stresses.  Dolphins rely on stored fats for energy reserves when food is in short supply, or when they are compromised due to illness.  For a dolphin storing a heavy load of toxins, the metabolizing of stored fats can result in a "toxic shock" as dangerous chemicals flood their system. 

Even animals carrying lesser loads of contaminants are susceptible to suppression of their immune systems.  This can cause them to succumb to bacterial and viral infections that they would normally handle. 

Most people consider the health of our oceans to be the responsibility of coastal communities.  However, vast amounts of pollution originate from inland villages, towns, and cities.  Many heavily populated areas reside along major river systems.  For example, the Mississippi River drains two-thirds of the continental area of the United States.  It also serves as a dump for industrial waste and sewage.  While most every county and city has local ordinances limiting the amounts of effluent allowed  into a particular stretch of waterway, the cumulative amounts are nearly immeasurable.  Agricultural run-off not only contains pesticides and herbicides, but also carries excess fertilizer; which in turn feeds algal blooms producing toxins and robbing the water of  huge amounts of oxygen.  Household chemicals disposed of down the drain also contribute a significant amount of pollution.  Regardless of where one lives, personal choices effect the health of the oceans.   

Choosing environmentally safe products, recycling, and disposing of wastes responsibly are a few ways that individuals can help protect our lakes, streams, rivers, and oceans.  In order to insure that higher standards for clean air and water continue to be legislated, citizens must participate in the election process --  at both federal and local levels.  

You can also assist the environment by expressing your opinion in letters to elected officials and corporate officers.  Staff members involved in public relations for these offices affirm that letters strongly influence the actions of their employers.