Abstract
Photo-identification methods depend on markings that are stable over time. Using a large dataset of photographs taken over a 31-year period, we evaluate the reliability, rate of change and demographic trends in different mark types on northern bottlenose whales (Hyperoodon ampullatus) in the Endangered Scotian Shelf population, and assess the prevalence and severity of anthropogenically caused markings. Only fin notches and back indentations were stable over long timescales, leading to 48% of the overall population being assessed as reliably marked. Males and mature males were found to have higher incidence of most mark types compared to females and juveniles. The proportion of reliably marked individuals increased over time, a trend that should be accounted for in any temporal analysis of population size using mark-recapture methods. An overall increase in marked individuals may reflect the accumulation of scars on an aging population post whaling. Anthropogenic markings, including probable entanglement and propeller-vessel strike scars, occurred at a steady rate over the study period and were observed on 6.6% of the population. The annual gain rate for all injuries associated with anthropogenic interactions was over 5 times the annual potential biological removal (PBR) calculated for the endangered population. As entanglement incidents and propeller-vessel strike injuries are typically undetected in offshore areas, we provide the first minimum estimate of harmful human interactions for northern bottlenose whales. With low observer effort for fisheries across the Canadian Atlantic, photo-identification offers an important line of evidence of the risks faced by this Endangered whale population.
| Original language | English |
|---|---|
| Article number | 620804 |
| Journal | Frontiers in Marine Science |
| Volume | 8 |
| DOIs | |
| Publication status | Published - May 5 2021 |
Bibliographical note
Funding Information:LF was responsible for project conception, funding acquisition, supervision, data collection, project administration, analysis, data visualization, writing, and editing. MS was responsible for data analysis, validation, visualization, writing, and editing. JY was responsible for data analysis, validation, visualization, and editing. CS was responsible for data analysis, validation, and editing. HW was responsible for funding acquisition, data collection, project administration, supervision, and editing. All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.
Funding Information:
We would like to acknowledge the contributions of three decades of volunteers and students that participated in the field and lab to collect and process the data used in this study. Wayne Ledwell and Julie Huntington of the Whale Release and Strandings Group in Newfoundland who reviewed and ranked photos of possible entanglement, providing much additional insight, the photograph of the whale in Figure 6C as well as some inspired whale poetry. Dr. Patrick Miller conducted fieldwork in the Gully in 2013 and Kristi O?Brien contributed photos of entangled Sowerby?s from those trips, which were important to the analysis conducted here. We gratefully acknowledge Dr. Hilary Moors-Murphy for their efforts to digitize the catalog and the funding support of Species at Risk and Oceans Management branches in the Maritimes Region of Fisheries and Oceans Canada. We would also like to recognize that Dalhousie University is located in Mi?kma?ki, the ancestral and unceded territory of the Mi?kmaq people. Without this support our research would not have been possible. Funding. This work was supported by grants and funding agreements with Species at Risk and Oceans Management branches in the Maritimes Region of Fisheries and Oceans Canada. In addition, LF and HW received funding from the Natural Sciences and Engineering Research Council of Canada and Killam Trusts. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Publisher Copyright:
© Copyright © 2021 Feyrer, Stewart, Yeung, Soulier and Whitehead.
ASJC Scopus Subject Areas
- Oceanography
- Global and Planetary Change
- Aquatic Science
- Water Science and Technology
- Environmental Science (miscellaneous)
- Ocean Engineering