What is an Unusual Mortality Event?

As defined under the Marine Mammal Protection Act, an unusual mortality event, or UME for short, is a stranding event that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response. There are currently three UMEs open for large whales that are seen in New York waters, including humpback whales, minke whales, and North Atlantic right whales.

How many large whales has AMSEAS responded to?

AMSEAS has been responding to large whale strandings in New York since 2017 as part of the Greater Atlantic Region Stranding Network. Since our inception, we have responded to 85 large whales, with 42% of those animals having evidence of human interaction. Of the large whales we’ve responded to, 27% have had evidence of vessel strike, and 13% have had evidence of entanglement. As of May 2023, AMSEAS has responded to 11 large whales from December 2022 to present.

Why are there so many whales in the waters off of New York and New Jersey?

Our colleagues at Gotham Whale, who have been collecting data on the whales in the New York Bight since 2011, have reported an increase in whale sightings over the last twelve years. This increase in sightings (and presumably whales in the area) may be attributed to several different factors. Firstly, the humpback whale population in the North Atlantic has grown in recent years. Additionally, these whales are often feeding on Atlantic menhaden (also known as “bunker”), which have also been seen in increasing numbers throughout the waters off of New York.

Why are whales being seen so close to shore?

One of the current theories among scientists is that warming ocean temperatures are culminating in a changing distribution of the whales in response to the changing distribution of their prey species, Atlantic menhaden. As the temperature in the North Atlantic is rising, it has been suggested that there have been declines in the whales’ prey species in other areas, and an increasing amount of bunker in the waters off of New York. In turn, the whales are being forced to adapt and thus move into new areas where conditions are more favorable (i.e., greater prey availability).

Menhaden have been reported especially close to shore in the New York Bight this winter. Humpback whales may simply be following their prey closer to shore.

What is the cause of recent whale deaths off of New York and New Jersey?

From NOAA Fisheries’ “Offshore Wind and Whales” FAQ page:

“In 2017, NOAA Fisheries declared an Unusual Mortality Event for humpback whale strandings along the Atlantic coast from Maine to Florida. The event is ongoing, and includes animals that stranded since 2016. As of May 2023, there are 194 humpback whale mortalities included in the UME. Partial or full necropsy examinations were conducted on approximately half of the whales. Of the whales examined, about 40 percent had evidence of human interaction, either ship strike or entanglement. Vessel strikes and entanglement in fishing gear are the greatest human threats to large whales.”

Out of the 11 large whales that have stranded off of New York and New Jersey since December of 2022, seven animals had evidence of human interaction. Six of the 11 whales had documented evidence of vessel strike.

Why are we seeing so many cases of vessel strike in large whales off of New York and New Jersey?

Large whales have been documented feeding inside the New York/New Jersey Harbor Estuary and in major shipping channels within the New York Bight. Whales may also be following their prey, Atlantic menhaden, closer to shore. This winter in particular juvenile humpback whales have been observed utilizing the waters off of New York and New Jersey as a winter-feeding ground, which is not typically the case with these animals. This observed change in behavior may be due to the warmer weather we’ve experienced this winter resulting in warmer ocean temperatures, and thus bringing a greater number of menhaden to the area.

Many of the whales that have been observed feeding close to shore have been engaging in lunge feeding, which is a behavior that puts them at greater risk for vessel strike due to the nature of feeding at the surface.

Additionally, menhaden are a prey species for other fish that are targeted by commercial and recreational fishermen, thus leading to a greater number of fishing boats in these already heavily trafficked areas.

During the fall of 2022 New York Harbor was declared the busiest shipping port in the nation, with massive vessels utilizing shipping lanes within the New York Bight. The combination of more whales in the area closer to shore, engaging in a feeding behavior that puts them at higher risk for vessel strike at the surface, along with more shipping and fishing activity with large tanker, cargo, cruise, and fishing vessels in the water has culminated into an overall increased risk for vessel strikes.

Is offshore wind development contributing to the whales’ deaths?

To date, no humpback whale mortality since the beginning of the current Northwest Atlantic humpback whale UME has been attributed to offshore wind activities. The Bureau of Ocean Energy Management and NOAA Fisheries also conducted rigorous assessments evaluating the potential impacts of High Resolution Geophysical surveys on marine mammals, and found that these surveys are not likely to injure whales or other endangered species.

Are offshore wind companies being given “incidental take” permits that authorize them to kill marine mammals?

Under the Marine Mammal Protection Act (MMPA), “take” means to harass, hunt, capture, or kill any marine mammal. It is worth noting that “take” does not always mean kill, and in the instance of offshore wind development, it is most often referring to harassment. “Harassment” under the MMPA can refer to any action that has the potential to injure a marine mammal (known as Level A harassment)” or “disturb a marine mammal by causing a disruption of behavioral patterns, including […] migration, breathing, nursing, breeding, feeding, or sheltering (known as Level B harassment)." Essentially, we are talking about Level A harassment as the potential for injury and Level B harassment as the potential for behavioral disturbance. An incidental take means that there is a potential for activity to have the unintended consequence of affecting marine mammals—it occurs as an unintended consequence but is not the purpose of the activity itself. This means, for example, that if a scientist is out on a boat conducting research while a whale is feeding in the area and the whale stops feeding to investigate the boat, that would be considered as a “take.” It would also be a considered a ”take” when recreational boaters approach whales on the water.

When there’s a proposed activity, such as construction, acoustic surveys, etc. that may result in the incidental take of marine mammals, the individuals or organizations involved in the activity must apply for an Incidental Take Authorization under the MMPA. Therefore, conducting ANY type of activity, from construction to scientific research, that could cause whales to change their behavior requires a “take” authorization.

The Incidental Take Authorizations that NOAA has issued associated with site characterization surveys have only authorized Level B harassment (i.e., behavioral disturbance), not Level A harassment and not mortality, as mortality cannot be authorized through the Incidental Take Authorizations that are involved in these surveys. The active permit applications for current surveys are listed publicly, and records show that all requested authorizations for off-shore wind energy surveys are non-lethal.

Is the offshore site survey mapping for the development of wind farms impacting the whales’ sonar and navigation, making them more prone to vessel strikes?

There is no scientific evidence that the sound sources used in offshore wind site surveys are attributed to injury or navigational interference for baleen whales. The surveys conducted in oil and gas exploration use seismic air guns, which are very loud, high-energy sources designed to penetrate very deep into the sea floor. The tools used for the site mapping surveys for offshore wind development are called high resolution geophysical sources (HRGs). BOEM’s Center for Marine Acoustics indicates that HRGs typically put out smaller amounts of acoustic energy into the water column, and are typically much lower in impact than seismic air guns.

Additionally, most of the large whales that have washed ashore are baleen whales. While toothed whales use echolocation for navigation and communication, baleen whales do not.

What measures are in place to ensure that the vessels involved in site survey work for offshore wind are following reporting regulations?

Part of the permitting process under Incidental Take Authorizations for offshore wind development surveys requires that vessels have independent protected species observers (PSOs), who are trained observers that have considerable survey experience, onboard during all survey work. These strict regulations require PSOs to be on duty at all times when the acoustic sources that may impact marine mammals are in use. In the event that a marine mammal or other protected species is observed by a PSO, an immediate shutdown of the acoustic sources is implemented and the interaction must immediately be reported. There are also mitigation measures in place that require vessels to travel at reduced speeds in times when marine mammals have been observed. Lastly, the Incidental Take Authorizations that have been issued require that should any vessel associated with the permitted activity strike a whale, they must immediately report it or face significant penalties.

Do you examine ear bones?

Ear bones can be examined to try and assess acoustic trauma, which could result from close exposure to loud human-produced sounds. However, this can be very challenging to assess in stranded cetaceans, particularly with any amount of decomposition. In order for an animal to float and wash ashore to begin with, the decomposition process has to have already begun. During necropsy examinations we look for bruising or trauma to the ear and other organs but linking it to a particular sound source is difficult. Collecting ear bones from large whales is also a very logistically complicated process, as it is challenging to access the part of the body where the ear bones would be because they are buried fairly deep near the skull and additional heavy equipment may be required to manipulate the skull to do so. This process is generally dependent on time, condition, and the availability of resources, and is more often done for toothed whales and small cetaceans where it's logistically more feasible to obtain them.

Additionally, the microscopic components of the ear bones that are vital to diagnosing acoustic trauma decompose very quickly (within hours). If the whale is already in a moderate to advanced state of decomposition, the microscopic indicators of trauma are generally no longer viable/detectable due to decay.

Our team has dedicated decades to understanding the causes of mortality of these animals.  Our dedication and concern is supported with the help of the public.  It is often easy to feel isolated when alone on the beach with a stranded animal, but the public support we receive in these instances is reassuring in highlighting the care the public has for our environment. We perform this tireless work because we value marine life and are dedicated to finding the answers to help conserve these majestic animals. We will continue to provide new information and updates as they become available. We thank you for your patience and understanding. For more information about the general necropsy process, visit our “All About Necropsies” page.