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Marine Mammal Strandings in New England and Mid-Atlantic Waters

What is a marine mammal “stranding”?

The Marine Mammal Protection Act defines a stranded marine mammal to mean any marine mammal that has died (beached or floating), or that is alive but is either beached, or in an area where it is not usually found. A live marine mammal that cannot return to its natural habitat under its own power or without assistance is considered stranded.

What are our goals when responding to marine mammal strandings?

IFAW and other volunteers perform necropsy on right whale yearling

When we respond to stranded or entangled animals, we focus on humane treatment of live animals, the safety of our responders, and scientific rigor in data collection, analysis, and peer review to inform future responses for both live and dead animals. Information gained from stranded animals can inform life history studies and population status and health.

What kinds of marine mammals strand in our region?

Many species of marine mammals either live in or migrate through New England and Mid-Atlantic waters (Virginia through Maine).  We have records of more than 30 different species that have stranded in our region. Strandings have included the three major categories we use to describe marine mammal species:

  1. Large whales include all the large baleen whale species, such as blue, fin, sei, right, humpback, and minke whales, and the largest toothed whale species, the sperm whale.
  2. Small cetaceans are smaller toothed whales, dolphins, and porpoise species. This group includes species such as beaked whales, pilot whales, bottlenose dolphins, and harbor porpoise. The small cetacean group is the most diverse group of marine mammals present in the New England and Mid-Atlantic waters. Toothed whales and dolphins are highly social species, and are at risk of mass stranding, or stranding in groups. Mass stranding response is a large component of the regional response efforts conducted by the Marine Mammal Stranding Network, particularly on Cape Cod, which is a hot spot for mass stranding events.
  3. Pinnipeds, meaning fin-footed, refers to walrus, sea lions or  fur seals (eared seals), and true seals (earless seals). Only earless seals or true seal species are present in the western North Atlantic. The most common seal species in the Greater Atlantic Region are harbor seals and gray seals. Arctic species, such as harp, hooded, and ringed seals are sighted or strand within the region during certain times of the year.

Find out more about marine mammal species in U.S. waters.

Why do marine mammals strand?

Marine mammals can strand because they are sick, injured, disoriented, or because they have died nearshore. While we are not always able to determine why an animal stranded, we do our best to gather as much information as possible. If an animal is severely decomposed, which is often the case when animals wash up on our shores, we may never know what caused it to die, but valuable information can still be obtained.

Frequency of Marine Mammal Strandings

On average, approximately a thousand marine mammals strand within the Greater Atlantic Region each year. Since the beginning of NOAA’s Marine Mammal Health and Stranding Response Program, and the formalization  of the Marine Mammal Stranding Network in 1992, there have been a total of 25,372 documented stranding events in the region (1992–2016). Large whale species made up 3% of the total strandings during this period, while small cetaceans made up 33% and pinnipeds 64%.

Marine mammal strandings from 1992-2016

Data Collection

We try to gather as much information as we can from examining carcasses and live stranded animals to better understand these species, as well as any population threats or pressures they may be facing.

From live animals that we rescue and rehabilitate, we learn about their biology,physiology, and disease risk and processes.

We also can learn a great deal from dead animals. We conduct a  a necropsy or animal autopsy and gather  information on their life history, the effects of pollution, normal biology and physiological parameters, reproductive biology, and pathology (diseases, parasites). We have also learned about the effects of human interactions, such as ship strikes, entanglements in fishing gear, hooks, and ingestion of marine debris. Necropsies give us the opportunity to find out more about the basic physiology and biology of animals that we otherwise would not be able to get from these animals in the wild, or through any other means

In most cases, necropsies of stranded marine mammals do not tell us precisely what caused the whale, dolphin, or seal to strand and die. We may be able to detect major traumas, as well as relative fitness or underlying disease factors, but those don’t always give a definitive answer as to why the animal died.

All of the information we glean from live and dead animals helps us make better management decisions about these stocks of marine mammals.

How can I help?

Everyone can help by reporting a stranding or disentanglement as soon as possible to our hotline 866-755-6622 or by radioing the US Coast Guard on Channel 16. Remember, leave the rescuing to the experts!

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