The IWC's population status assessment process is science-based, using data-driven population estimates and, when possible, a computer-modelling approach.
These status assessments are not undertaken by species but by population or sub-population (also known as 'stocks'). This approach is necessary because the majority of whale, dolphin and porpoise species are found across large geographic areas and are often subdivided into distinct groups. Within a single species there may be one population struggling to survive whilst another is believed to be thriving. A good example of this is the North Pacific gray whale, where status is considered good in the eastern North Pacific but very poor in the west.
Status of Whales: the IWC Scientific Committee's Population Assessments
The Scientific Committee uses computer models to compare current population size to a chosen point in the past (e.g. prior to commercial whaling)
or to an estimated maximum size that the habitat can currently sustain, and predict where is it likely to go in the future (e.g. increasing, decreasing, remaining the same). These models combine population size estimates with other information compiled over many years to track population trends over time. The model predictions also account for natural deaths and births, identified trends, known and quantifiable threats, and human-induced deaths.
The Scientific Committee has been developing and refining these modelling approaches for decades, producing status assessments in support of a
range of core, long-standing tasks related to conservation and management actions, ranging from ensuring sustainable catch limits for Aboriginal Subsistence Whaling to assessing the impact of ship collisions. 
These webpages include population status assessments presented in a new format that is both detailed and accessible. Additional assessments will
be added annually, as they are completed and endorsed.
These assessments represent the Scientific Committee’s best judgments about the status of whale stocks and provide a unique, detailed view of status.
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IWC's new Status of Whales Table using at-a-glance graphics
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Short text summary of status for each whale species here
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Learn about how status assessments help mitigate threats to whales
Threats to cetaceans are categorised as either short-term threats with a direct impact on individual animals, for example whaling or bycatch in fishing gear, or longer-term threats which are more difficult to recognise and quantify, but may impact on the heath of an entire population, for example chemical pollution or climate change.
Information about status is needed to evaluate threats to populations and decide the urgency with which conservation action is required. A critically endangered population might struggle to survive the loss of just one mature female, but a thriving and abundant population will be more resilient and therefore less likely to require an immediate response, or possibly any human intervention at all.
Learn about the challenges involved in conducting assessments
It is not easy to accurately estimate the number of animals in any population because they are constantly moving, often over large areas, and usually under water or ice. Many inhabit the world's most remote regions.
Evaluating the status of a population usually requires an understanding of its original, undisturbed size prior to human activity, predominantly industrial whaling. This relies on historical data which may be incomplete or inaccurate.
Whales are long-lived, take a long time to reach maturity, and only have one calf every 1-3 years, so estimating population trends can only be accomplished with consistent monitoring over a long period of time.
Determining population structure, particularly for populations where the breeding grounds are unknown, is difficult.
Biological information like mortality and reproduction rates are poorly known for most whale species. Models for how populations change over time are also only approximations.
Learn about scientific uncertainty and how this is incorporated into population status assessments
Estimating the level of uncertainty (and thus the ‘confidence limits’ for the results produced) is a fundamental aspect of research in any field of science. Whale population status assessments are subject to many uncertainties such as those described above. The underlying data (such as population estimates) can only provide limited, imperfect indicators of the true situation.
The IWC’s Scientific Committee has developed a range of techniques and guidelines to assess populations and quantify uncertainty. Model-based assessments address and incorporate uncertainties by investigating wide ranges of scenarios and applying statistical approaches to quantify and account for uncertainty in model structure, data-based evidence, and assumptions.
When reading about these assessments, it is important to look at the ranges of uncertainty provided, in addition to the primary estimates, in order to fully understand the limits of what we know about each particular population’s status. Furthermore, future marine environments can be unpredictable in ways that models may not anticipate.
Different types of population assessment
The IWC collaborates with the International Union for Conservation of Nature (IUCN) and makes use of IUCN Red List assessments of status where appropriate. Red List assessments in turn, often make use of the work by the IWC Scientific Committee. The IUCN Red List Categories and Criteria are intended to provide an easily and widely understood system for classifying species according to their risk of extinction. The system is designed to apply to all wild species – whales, birds, plants, invertebrates, even fungi – using nine status categories: Not Evaluated, Data Deficient, Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild and Extinct. IUCN Red List assessments are compilations of information on current extinction risk that typically focus on species rather than population units. However, because the range of most whale species spans huge geographic distances, a population in one location may be at a high risk while a population of the same species in a different location may be quite abundant and less threatened. The IUCN’s Cetacean Specialist Group is responsible for producing Red List assessments for all cetaceans following the IUCN Red List Guidelines. The group is seeking to produce more assessments to categorise threat at a finer resolution, below the species level, for the most threatened sub-populations. This scale is more akin to the IWC’s approach and gives a better idea of which specific whale, dolphin, and porpoise populations are at the greatest risk.
See here for more information.
Learn about IWC Extinction Alerts
Read more
Introductory pages
Status of Whales: At-a-Glance Table
Status of Whales - Text Summaries
Further information
Technical Methods
Glossary
