Abigail Machernis, PWF research biologist and lead author of the paper, reviewed data collected from the Maui Nui area of ​​Hawai’i, which includes the islands of Maui, Moloka’i, Lana’i and Kaho’olawe and found that 27% of the 255 identified bottlenose dolphins and 13% of the 374 spotted dolphins identified had one or more scars related to the fishing gear. Each image in the association’s extensive catalog of passport photos has been examined to identify dolphins with scars on the dorsal fins, mouth lines and bodies of dolphins that indicate past interactions with fishing and fishing gear. . The objectives of PWF’s research were (1) to determine the number of bottlenose and spotted dolphins that showed evidence of interaction with fishing in Maui Nui; and (2) to determine whether underwater body images, in addition to traditionally used dorsal fin and buccal line images, have increased detection rates for evidence of fisheries interactions.

Building on an established methodology, focusing primarily on dorsal fin analysis, the researchers used underwater body images to gain a new perspective to assess interactions with fisheries. The inclusion of underwater photo analysis was a game-changer, according to Machernis. “Most of the research papers that look at interactions between fisheries focus on dorsal fins and we wanted to use all the data we collected to examine as much as possible the bodies of dolphins for scars related to fishing gear. . “

The study’s innovative approach involves combining individual assessments of dolphins’ dorsal fins, mouthlines and bodies into a single assessment and found that the inclusion of underwater images increased scar detection rates. 51% for bottlenose dolphins and 40% for spotted dolphins. Using previous research on fisheries interactions and cutting-edge research methods, the study is the first to present a standardized approach for using photos of dorsal fins, mouthlines and underwater body footage. in the assessment of interactions with fisheries.

“Without documenting real-time interactions or observing physical gear on an animal’s body, photographic analysis is the best available proxy for quantifying interactions with fisheries,” notes Currie. “There is still more research to be done and we want to make sure we have all the information we need to determine if there is a conservation problem, and then work with fishermen on a solution if necessary.”

Worldwide, interactions with fisheries have been identified as one of the primary conservation concerns for cetaceans, with fatal and non-fatal consequences. The total extent is difficult to assess because most entanglements are never seen, but research noted by the International Whaling Commission (IWC) suggests that more than 300,000 whales and dolphins die each year due to entanglement in marine debris. This can have a devastating and long-term impact on the conservation of already threatened populations, in some cases critically.

Past and ongoing research confirms that direct interactions between cetaceans and fishing gear generally occur in one of two ways: (1) the animals unwittingly swim in the gear by becoming entangled or trapped, or ( 2) Animals deliberately remove captured fish from gear, a behavior known as depredation, and become addicted and / or entangled as a result. Certain interactions with fishing gear can result in serious injury or death from entanglement or ingestion of gear.

These types of interactions occur on a global scale and are likely to increase due to the potential for continued human encroachment on cetacean habitats. Thus, states the document, the impacts of fishing on cetaceans at the population level are of great concern and it is essential to identify which species interact with which fisheries and the location (s) where these interactions occur so that researchers can work with fishermen to find sustainable solutions. solutions.

In short, Machernis concludes that these results suggest that interactions with fisheries are more widespread than we previously thought, and this may have implications for how we manage these populations associated with near-shore islands. In addition to informing management and conservation actions, the study and document supports outreach efforts targeting recreational and commercial fishermen who provide education on best fishing practices when dolphins are present.

“We strongly recommend that researchers interested in examining the threat of fishing interactions to dolphins make a concerted effort in the field to collect images of the mouth and body above the water, in addition underwater images, “advises Machernis, emphasizing the value of images such as those studied in providing a more accurate analysis of scar detection rates.

PWF scientific article, External scars as an indicator of fishing interactions with bottlenose dolphins (Tursiops truncatus) and spotted pantropicals (Stenella attenuata) in Maui Nui, Hawai’i Written by Abigail Machernis, Stephanie H. Stack, Grace L. Olson, Florence A. Sullivan and Jens currie, is published in Aquatic mammals and available for review. All Pacific Whale Foundation publications are available free at PacificWhale.org/research/publications.

To learn more or make a contribution to support PWF’s dolphin research, please visit PacificWhale.org/pacific-whale-foundation/.

About the Pacific Whale Foundation
With a mission to protect the ocean through science and advocacy and to inspire environmental stewardship, the Pacific Whale Foundation (PWF) conducts research, education and conservation programs. Founded in 1980 as a 501 (c) (3) nonprofit dedicated to saving the world’s whales from extinction, PWF now only owns the social enterprise PacWhale Eco-Adventures, which offers programs and paid services to help support the non-profit organization. Combined with memberships, donations, charitable grants and a remarkable group of dedicated volunteers, PWF now reaches over 400,000 people each year through its offices in Maui and Australia and its research projects in Ecuador and Chile.

SOURCE Pacific Whale Foundation