Investigators : Dr. Leigh G. Torres, Dr. Solène Derville, Craig Hayslip, John Calambokidis (CRC), Dr. Lindsay Wickman

Summary
  • Whale entanglements are both under-detected and under-reported on the U.S. West Coast
  • Previous entanglements often lead to wrapping scars and notches on the flukes and peduncle (tailstock). We can therefore use photographs of these scars to assess trends in entanglement-related scarring in humpback whales off the Oregon Coast
  • Between 8–27% of humpback whales in Oregon waters were determined as likely or most likely entangled at least once in their lifetime
  • Males were more likely to be entangled than females
  • Trends in entanglement scar rates over time and among sub-populations are currently uncertain, but will be explored in future capture-recapture modeling

 

Background

Reports of whale and other marine life entanglements have been on the rise over the last decade on the US West Coast, with Dungeness crab fishing gear implicated in many cases. State agencies play a critical role in managing this major environmental issue that has implications both for the endangered humpback whale sub-populations threatened by entanglements, and for the persistence of fishing activities, which play an important social, cultural, and economic role for coastal communities.

Current entanglement monitoring primarily relies on opportunistic reports from ocean users. However, entanglements off the U.S. West Coast are notoriously under-detected and under-reported (Tackaberry et al., 2022).

Alternatively, scar-based methods using photographs can be used as a proxy to detect undocumented whale entanglement events. Photographs of different parts of the whale’s body, particularly the tailstock, are examined for wrapping scars and notches indicating a previous entanglement.

The SLATE project includes three main tasks:

  • collecting, compiling, and processing photographic data to assess scarring rates
  • engaging with interested fishermen to collect photographs of whales
  • developing statistical analyses to monitor rates of undocumented entanglement takes in Oregon

 

Findings

We analyzed 1,533 photos of 571 individual humpback whales photographed in Oregon, USA, waters during 2005–2023. Photographs were collected by Cascadia Research Collective, Oregon State University, a local whale watching operator (Whale Research EcoExcursions) and by three volunteer fishermen photographers. Through SLATE’s fishermen photographer program, interested fishermen were provided a camera, basic instruction in photography and NOAA’s marine mammal observation guidelines, and a small stipend.

Depending on scoring approach, between 8.2–27.3% of humpback whales photographed the Oregon Coast were estimated as non-lethally entangled at least once in their lifetime. The underside of the flukes was the most common type of photo in our dataset (since they are commonly collected for individual identification purposes), but they were the least likely to show entanglement scars. Photos perpendicular to the tailstock, however, were most likely to show entanglement scars.

We also found evidence of demographic differences in entanglement scarring. Males had more entanglement scars, with 16% categorized with “most likely” entanglement-related scarring (n=13 out of 80 males), compared to 4% of females (n=2 out of 54 females).

 

Current work

Trends in the rates of entanglement scars of humpback whales in Oregon waters is currently uncertain. It is also uncertain whether management action (i.e., a 2022 regulation restricting commercial Dungeness crab fishing to waters less than 40 fathoms after May 1) have affected scarring rates.

Therefore, we aim to continue this work using capture-recapture modelling to assess scarring rates over time. Future work also aims to resolve scarring rates at the sub-population level. Humpback whales along the Oregon Coast are comprised of multiple sub-populations, or stocks, based on the breeding ground they migrate from (Mexico, Central America, and Hawaii). These stocks are recognized by the U.S. Endangered Species Act (ESA) as Distinct Population Segments (DPS), each with different threat classifications. By estimating scarring rates for each DPS, we can improve our understanding of the relative impacts of entanglement on each DPS in Oregon.

 
Blogs and Media

Disentangling the whys of whale entanglement

Announcing our new project: SLATE – Scar-based Long-term Assessment of Trends in whale Entanglements

OSU-led project aims to reduce whale entanglements in Oregon and beyond

“Thar she blows!” OSU Researchers study whale/fishing gear incursions

Daylong expedition to sea gives Waldport High students a taste of scientific research and ship life

 

Funders

Direct congressional Community Project Funding run through NOAA Fisheries and the Oregon Department of Fish and Wildlife (ODFW)

Oregon Sea Grant

 

Collaborators

Troy Buell and Kelly Corbett (Oregon Department of Fish and Wildlife)

Dr. Scott Baker (Cetacean Conservation and Genomic Laboratory, OSU Marine Mammal Institute)

Dr. Daniel Palacios

Cascadia Research Collective

Fishermen photographers: Cyle Barnhart, Aaron Ashdown, and Josh Allman

STEM at Sea: Tracy Crews

Whale Research EcoExcursions: Carrie Newell

 

Publications

Derville, S., Calambokidis, J., Palacios, D., Tackaberry, J., Hayslip, C., Flynn, K., New, L., Baker, C., Steel, D., Martien, K., Moore, J., Lauf, M., Wickman, L., Wall, A., Newell, C., & Torres, L. (2025). Rates of entanglement inferred from scarring prevalence of humpback whales photographed in US Oregon waters. Endangered Species Research, 57, 253–271. https://doi.org/10.3354/esr01416

 

 

Whale entanglements are notoriously under-reported, so photographs of entanglement-related scarring are being used to better understand this issue in humpback whales.

Basran, C. J., Bertulli, C. G., Cecchetti, A., Rasmussen, M. H., Whittaker, M., & Robbins, J. (2019). First estimates of entanglement rate of humpback whales Megaptera novaeangliae observed in coastal Icelandic waters. Endangered Species Research, 38(February), 67–77. https://doi.org/10.3354/ESR00936

Bradford, A. L., Weller, D. W., Ivashchenko, Y. v., Burdin, A. M., & Brownell, R. L. (2009). Anthropogenic scarring of western gray whales (Eschrichtius robustus). Marine Mammal Science, 25(1), 161–175. https://doi.org/10.1111/j.1748-7692.2008.00253.x

George, J. C., Sheffield, G., Reed, D. J., Tudor, B., Stimmelmayr, R., Person, B. T., Sformo, T., & Suydam, R. (2017). Frequency of injuries from line entanglements, killer whales, and ship strikes on bering-chukchi-beaufort seas bowhead whales. Arctic, 70(1), 37–46. https://doi.org/10.14430/arctic4631

Knowlton, A. R., Hamilton, P. K., Marx, M. K., Pettis, H. M., & Kraus, S. D. (2012). Monitoring North Atlantic right whale Eubalaena glacialis entanglement rates: A 30 yr retrospective. Marine Ecology Progress Series, 466(Kraus 1990), 293–302. https://doi.org/10.3354/meps09923

Robbins, J. (2012). Scar-Based Inference Into Gulf of Maine Humpback Whale Entanglement : 2010 (Issue January). Report to the Northeast Fisheries Science Center National Marine Fisheries Service, EA133F09CN0253 Item 0003AB, Task 3.

Tackaberry, J., Dobson, E., Flynn, K., Cheeseman, T., Calambokidis, J., & Wade, P. R. (2022). Low Resighting Rate of Entangled Humpback Whales Within the California , Oregon , and Washington Region Based on Photo-Identification and Long-Term Life History Data. Frontiers in Marine Science, 8(January), 1–13. https://doi.org/10.3389/fmars.2021.779448

van der Hoop, J., Corkeron, P., & Moore, M. (2017). Entanglement is a costly life-history stage in large whales. Ecology and Evolution, 7(1), 92–106. https://doi.org/10.1002/ece3.2615