MMR staff assists NOAA Fisheries with Common Dolphin case

Posted on November 5, 2023

Brian Yurasits | Marine Mammal Rescue Community Outreach Manager

Please be advised that there are photos of the deceased animal in this post.

11.6.23 Update

On Monday, October 30, 2023, Seacoast Science Center Marine Mammal Rescue staff assisted partners NOAA Fisheries New England in response to reports of a deceased common dolphin in Mill Pond in Gloucester, MA. To learn what happened to this animal, responders extracted the dolphin and transported it to New Hampshire Veterinary Diagnostic Laboratory for a full necropsy (animal autopsy) and histopathology. Although full results will take time, initial findings indicate that the animal was suffering from a necrotizing brain lesion likely caused by trematode parasites or fungus. Additionally, the animal was found to have a suspected lungworm infection.

Initial Response

swimming dolphinThis common dolphin was first reported to NOAA Fisheries around 12pm on Friday, October 27, 2023. The reporting party sent videos and photos that showed the animal freely swimming in Gloucester’s Mill River, but in circles. This location is an intertidal river located near Wingaersheek Beach, which meets the Annisquam River and eventually flows into Annisquam Harbor. The tide was dropping when a team of responders including Seacoast Science Center, NOAA Fisheries, and Gloucester Deputy Shellfish Constable arrived on-site to assess and monitor the animal. Throughout the afternoon, the animal remained in the deeper-sections of the intertidal area, freely-swimming slowly. This common dolphin was an adult male that appeared to be in relatively good body condition, and with no external signs of human interaction or significant injuries. Initially, he was observed by our responders to be swimming in circles, and listing (leaning) to one side. These are signs that can indicate the dolphin is sick or injured.

During a live dolphin response, the best scenerio would involve guiding a freely-swimming animal toward deeper, open water. There aren’t any long-term rehabilitation facilities that can care for dolphins in our region, so our team continuously monitored the animal as it swam in Mill River. The low tide and timing made it difficult to attempt to herd the animal into deeper waters by vessel, but the team stood by ready to re-float or re-locate the animal if it became stranded. The sun was setting when our team decided to return in the morning, after the tide had risen again

The animal was not seen again until 3 days later, despite efforts to monitor the area by vessel.

Second Response

Around 1pm on Monday, October 30th, a stranded dolphin in Mill Pond was reported to the Gloucester Animal Control Officer. A responder from SSC’s MMR team was able to determine that this was the same animal that was last seen alive in Mill River. The animal was secured to an accessible area of the pond using a boat anchor and rope, while responders developed a plan to extract this 7 foot long animal from the intertidal mudflat that it was stranded in.

Deceased common dolphin on mudflat.
The intertidal mudflat posed unique challenges for our team to successfully extract the animal to conduct a necropsy. Thankfully, our responders were able to secure the animal to shore using a boat anchor (rope pictured here), and extract the animal when the tide was low. The animal was marked with the date using pink livestock marker, as seen in this image. The common dolphin’s unique ‘hourglass’ coloration can be clearly seen here.
SSC MMR responding team collecting length measurements, swam samples for disease surveillance, and photos of the animal before transporting for a full necropsy.
Our responding team collected length measurements, swab samples for disease surveillance, and photos of the animal before transporting for a full necropsy.

On October 31st, the animal was successfully removed from Mill Pond and transported to the New Hampshire Veterinary Diagnostic Laboratory for a full necropsy to learn more about this animal’s condition, and cause of death.

Necropsy Results

Full results of the necropsy and histopathology will take time (and will be updated here in this blog), but initial findings indicate that the animal was suffering from a necrotizing brain lesion likely caused by trematode parasites or fungus. Additionally, the animal was found to have a suspected lungworm infection.

Although this outcome was unfortunate, our team was able to collect crucial information to help us learn more about why this animal stranded, and what sources of mortality this species experiences.

About Common Dolphins

Common dolphins are a native species to the Gulf of Maine, and it is common to see this species year-round. These dolphins have a unique color pattern that many refer to as an ‘hourglass’. Common-dolphins often live in large social groups offshore, spending time actively at the surface, and typically diving 100 feet deep to hunt schooling fish and cephalopods. These charismatic mammals grow to an average of 6 feet in length, and can live up to 35 years.

How to Help

If you ever see a dolphin, dead or alive, please keep at least 150 feet away and report the animal to your local Marine Mammal Rescue hotline.  Seacoast Science Center Marine Mammal Rescue’s territory includes from Essex, MA, north to the Maine border. Our 24/7 response hotline is 603-997-9448. For areas outside SSC’s range, please call the NOAA hotline at 866-755-6622 to be directed to responders in that area.

All marine mammals are federally protected by the Marine Mammal Protection Act; it is illegal to harm, harass, or kill any marine mammal species in the United States.

SSC’s MMR team is able to successfully respond to an average of 130 seals, whales, dolphins, and porpoises each year thanks to the generous support of our volunteer team, donors, and community partners.

Volunteer Alyssa measure the girth of the dolphin.
A HUGE thanks to our Gloucester volunteers, including Alyssa pictured here, who have been very busy lately assisting our partners NOAA Fisheries New England/Mid-Atlantic with marine mammal responses in the Cape Ann area.

Seacoast Science Center will be CLOSED today: Friday, April 5, 2024. Our utilities are currently down and need to get repaired before we are able to open for visitors. Thank you for your understanding. 

CLOSED today.

Seacoast Science Center is closed today due to inclement weather.