Threats to whales and dolphins
Intentional Take
The global moratorium on commercial whaling came into place in 1986 but over 30,000 whales have been killed since then by Japan, Iceland and Norway in various guises. Small scale, localised drive hunts are also undertaken by various coastal communities around the world, resulting in the deaths of thousands more whales and dolphins. For more information click here.
Bycatch
The main killer of whales, dolphins and porpoises around the world is fishing equipment: nets, lines, traps, hooks and other gear. There is no ocean, sea-area or even river where this is not a serious issue and hundreds of thousands of cetaceans are dying from fishing related causes every year. For more information click here.
Vessel Strikes
Whales and dolphins are usually able to avoid vessels, but with more and ever-faster ships, traffic on the sea has become ever more dangerous to these animals. Whales and dolphins can suffer life-threatening injuries as well as sometimes being killed outright when struck. In some parts of the world, vessel strikes happen so often that they threaten the survival of endangered species, or populations. For more information click here
Climate Change
Changes in sea temperature, freshening of seawater, sea level rise, loss of icy polar habitats and the associated declines of food sources are the key threats posed by climate change. For more information click here.
The global moratorium on commercial whaling came into place in 1986 but over 30,000 whales have been killed since then by Japan, Iceland and Norway in various guises. Small scale, localised drive hunts are also undertaken by various coastal communities around the world, resulting in the deaths of thousands more whales and dolphins. For more information click here.
The main killer of whales, dolphins and porpoises around the world is fishing equipment: nets, lines, traps, hooks and other gear. There is no ocean, sea-area or even river where this is not a serious issue and hundreds of thousands of cetaceans are dying from fishing related causes every year. For more information click here.
Whales and dolphins are usually able to avoid vessels, but with more and ever-faster ships, traffic on the sea has become ever more dangerous to these animals. Whales and dolphins can suffer life-threatening injuries as well as sometimes being killed outright when struck. In some parts of the world, vessel strikes happen so often that they threaten the survival of endangered species, or populations. For more information click here
Changes in sea temperature, freshening of seawater, sea level rise, loss of icy polar habitats and the associated declines of food sources are the key threats posed by climate change. For more information click here.
There are many different sources of chemical pollution: domestic sewage discharges to rivers and the sea, industrial discharges, seepage from waste sites, atmospheric deposition, domestic run-off, accidents and spills at sea, operational discharges from oil rigs, mining discharges and agricultural run-off. As marine top predators, cetaceans are very vulnerable to the effects of those contaminants that build up in marine food chains and such substances can depress their reproductive ability and lead to ill health.
Of all their senses, hearing is the one on which cetaceans rely most. The background noise in the ocean has nearly doubled every decade since the 1950s. An increasing amount of noise pollution in the marine environment can have a number of effects, ranging from disturbance and masking of important sounds, to, in the case of very loud noises, fatal impacts. For more information click here.
Disturbance can be caused by industrial activities at sea, military exercises and actions, aircraft, recreational and commercial shipping and even whale and dolphin watching. Most boat operators, commercial and recreational, are careful and act responsibly around marine life but, in some locations, wild whales or dolphins are harassed and repeatedly disturbed by boats. There is concern that disruption to feeding, resting, nursing and other behaviour has not only a short-term but may have a long-term impact on the health and well-being of individuals and populations.
The modification of habitats, including land reclamation, coastal development and disturbance from industrial activities including but not limited to exploitation of the seabed, can make habitats unsuitable for populations of whales, dolphins and porpoises. Cetaceans may also be driven from their preferred habitats if click here
Fishing may result in a reduction in prey availability or prey quality (as we select the more energy-rich fish for our tables, for example). Climate change may also be having a role to play in changing prey availability. Some cetaceans may be able to adapt and find alternative food, but others may have no alternative food source, or only poorer quality alternatives, and may suffer as a result.
Also known as marine litter, this is human-created waste that has deliberately or accidentally entered the marine environment. Cetaceans may be harmed when they become entangled in such materials (for example discarded fishing nets) or they may even ingest them. Discarded plastic bags may be mistaken for food and, once swallowed, block an animals digestive system leading to the death of the animal.
Live capture for the aquarium industry is a threat to the survival of some species and populations, with unknown consequences for the populations targeted. Torn from their family groups and transported sometimes thousands of miles for public display, shows and interaction programmes, the lives of the captives are often short-lived. For more information on the species and populations targeted by the captivity industry and the impact of capture and confinement on the individuals kept in captivity click here.
Cumulative Concerns
The guide spotlights separate categories of threats but the reality for many populations is that they are being affected by various threats at the same time. Often these threats build one upon another to create an even bigger problem. For example the problems caused by fishing removing prey may in many cases be made worse by climate change also impacting prey populations and reducing their ability to reproduce and recover. Dolphin watching by itself may be fine, but if the population is stressed through chemical and noise pollution and is having trouble finding prey, then the watching activity may be more significant and in combination all these stressors may produce a situation where the population cannot maintain itself.
© WDCS, the Whale and Dolphin Conservation Society, 2010. Registered UK Charity No. 1014705. All photographs presented by kind permission of the copyright holders.