Nav: Home

Dolphin calf entangled in fishing line only lived two years following rescue

August 04, 2020

More than 1,000 bottlenose dolphins (Tursiops truncatus) live in the Indian River Lagoon year-round. The estuary system along the central east coast of Florida stretches about 250 kilometers and provides valuable shallow water habitat for this species. The lagoon also is popular for recreational fishing spots, which often coincide with bottlenose dolphin feeding habitats because they target the same species of fish. In fact, it very common to observe interactions between dolphins and recreational fishermen. These interactions include dolphins going after bait or captured fish, illegal feeding of dolphins, and dolphin encounters during release of undersized or non-targeted fish.

Unfortunately, free-ranging common bottlenose dolphins can become entangled in fishing line and other marine debris. Reports of entanglement include a variety of items such as crab trap lines, human clothing, spearfishing gear, Frisbees, box strapping, and other objects. Infrequently, dolphins can be successfully disentangled and released back into the wild. It is rare, however, to encounter a case that can be followed from physically handling the dolphin at a disentanglement event to later recovering its carcass, enabling pathologic descriptions after an entanglement wound has healed.

Researchers from Florida Atlantic University's Harbor Branch Oceanographic Institute and collaborators from Earth Resources Technology, Inc., the National Marine Mammal Foundation, and Georgia Aquarium Conservation Field Station, conducted a case study to examine the outcome of an entangled bottlenose dolphin calf found in the Indian River Lagoon with monofilament fishing line wrapped tightly around its maxilla or upper jaw. A multi-agency team successfully disentangled the dolphin and immediately released it back into its natural habitat.

Because local bottlenose dolphin populations demonstrate site fidelity to the Indian River Lagoon, they are relatively easy to re-sight and monitor. The shallow, soft substrate in several inshore areas along the lagoon also allows for safe targeted capture and disentanglement efforts involving appropriately skilled biologists and veterinarians in cases where entanglements are deemed life threatening.

For the study, published in the journal BMC Veterinary Research, the researchers compared data collected on presentation during the disentanglement event to data later collected during re-sighting and necropsy. Results demonstrate long-term damage from the entanglement involving maxillary bones, dentition and soft tissues of the rostrum or snout. One year after disentanglement, photos and visual observations indicated that the now independent calf showed a decline in body condition, characterized by grossly visible ribs and a prominent post-nuchal depression, also known as "peanut-head," a prominent depression behind the skull, which is indicative of poor nutritional condition.

More than two years post-disentanglement, the freshly dead carcass of this juvenile dolphin was recovered with extensive predation wounds. Despite the forestomach being about?50 percent full of fish, the dolphin was emaciated. During postmortem examination, researchers collected and evaluated detailed photographs and measurements of the maxillary damage resulting from the entanglement.

"Entanglements in cetaceans such as dolphins can impede movement and impair foraging abilities, leading to starvation, systemic infections, and debilitation from severe tissue damage, pain and distress, and in some cases, death," said Annie Page-Karjian, D.V.M., Ph.D., assistant research professor and clinical veterinarian at FAU's Harbor Branch, who co-authored the paper with Wendy Marks, program coordinator, and Steve Burton, M.S., program director of stranding and population assessment, who are all members of the marine mammals stranding, health and rehabilitation project team.

The monofilament entanglement caused permanent, bilateral deformation of the maxillary dental arcade, including a 4 to 4.2?centimeter long, 0.5?centimeter deep linear groove where the entanglement eroded the lateral edges of the maxilla. Entanglement in this 2-year-old dolphin did not cause bone fracture but did lead to bone deformity and maxillary malocclusion. External evidence of propeller scars and a fishing hook was discovered embedded in the laryngeal mucosa at necropsy, indicating repeated human interactions. The dolphin only survived for about two years after disentanglement and release.

"Educating fishermen about the importance of reeling in their lines when dolphins are present and proper disposal of fishing line can help reduce the risk of these interactions with bottlenose dolphins," said Page-Karjian. "Less lost fishing gear and fewer injured or dead marine wildlife benefits everyone. While the quick response to disentangle this dolphin may have initially saved its life, prevention of learned fishery interaction behaviors could have prolonged his life beyond the two plus years that were gained."
-end-
This work was supported by Protect Wild Dolphins License Plate Funds, granted through the Harbor Branch Oceanographic Institute Foundation. The disentanglement intervention was funded by National Marine Fisheries Services (NOAA Fisheries) through a contract with the University Corporation for Atmospheric Research (UCAR).

About Harbor Branch Oceanographic Institute:

Founded in 1971, Harbor Branch Oceanographic Institute at Florida Atlantic University is a research community of marine scientists, engineers, educators and other professionals focused on Ocean Science for a Better World. The institute drives innovation in ocean engineering, at-sea operations, drug discovery and biotechnology from the oceans, coastal ecology and conservation, marine mammal research and conservation, aquaculture, ocean observing systems and marine education. For more information, visit http://www.fau.edu/hboi.

About Florida Atlantic University:

Florida Atlantic University, established in 1961, officially opened its doors in 1964 as the fifth public university in Florida. Today, the University, with an annual economic impact of $6.3 billion, serves more than 30,000 undergraduate and graduate students at sites throughout its six-county service region in southeast Florida. FAU's world-class teaching and research faculty serves students through 10 colleges: the Dorothy F. Schmidt College of Arts and Letters, the College of Business, the College for Design and Social Inquiry, the College of Education, the College of Engineering and Computer Science, the Graduate College, the Harriet L. Wilkes Honors College, the Charles E. Schmidt College of Medicine, the Christine E. Lynn College of Nursing and the Charles E. Schmidt College of Science. FAU is ranked as a High Research Activity institution by the Carnegie Foundation for the Advancement of Teaching. The University is placing special focus on the rapid development of critical areas that form the basis of its strategic plan: Healthy aging, biotech, coastal and marine issues, neuroscience, regenerative medicine, informatics, lifespan and the environment. These areas provide opportunities for faculty and students to build upon FAU's existing strengths in research and scholarship. For more information, visit fau.edu.

Florida Atlantic University

Related Dolphins Articles:

Study finds high levels of toxic pollutants in stranded dolphins and whales
Researchers examined toxins in tissue concentrations and pathology data from 83 stranded dolphins and whales from 2012 to 2018.
Tracking humanity's latest toxins in stranded whales and dolphins
As humanity develops new types of plastics and chemicals, researchers are constantly trying to keep up with understanding how these contaminants affect the environment and wildlife.
Young dolphins pick their friends wisely
Strategic networking is key to career success, and not just for humans.
Dolphins learn foraging skills from peers
Dolphins can learn new skills from their fellow dolphins. That's the conclusion of a new study reported in the journal Current Biology on June 25.
Dolphins learn in similar ways to great apes
Dolphins learn new foraging techniques not just from their mothers, but also from their peers, a study by the University of Zurich has found.
Shelling out for dinner -- Dolphins learn foraging skills from peers
Dolphins use empty gastropod shells to trap prey. A new study demonstrates for the first time that dolphins can learn this foraging technique outside the mother-calf bond - showing that they have a similar cultural nature to great apes.
Good night? Satellite data uncovers dolphins on the move at nighttime
More than 1,000 bottlenose dolphins live in Florida's Indian River Lagoon year-round.
Cooperative male dolphins match the tempo of each other's calls
When it comes to working together, male dolphins coordinate their behavior just like us.
Dolphins gather in female family groups
Social clusters including mothers' groups play an important role in the life of southern Australian bottlenose dolphins, a new study shows.
Lights on fishing nets save turtles and dolphins
Placing lights on fishing nets reduces the chances of sea turtles and dolphins being caught by accident, new research shows.
More Dolphins News and Dolphins Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.