This web application uses cookies and other tracking technologies to ensure you get the best experience.
SC/69B/SH/16
Download this file2.2 MB |
Download |
View directly in browser2.2 MB |
View in browser |
Resource ID
22158
Access
Open
Document Number
SC/69B/SH/16
Full Title
Progress report on capture-recapture analysis of bilateral photo-ID data for Chilean blue whales
Author
Rachel M. Fewster And Rishika Chopara
Authors Summary
Fewster and Chopara presented a progress report on the capture-recapture analysis of bilateral photo-ID data for southern hemisphere blue whales, using left/right photo-ID data from the Southern Hemisphere Blue Whale Catalogue. They described their modelling approach, including new methods for incorporating unreconciled left-and right-side photos into a single analysis. They presented preliminary findings for data from two Chilean feeding grounds, estimating that the population in the southern site (vicinity of Isla Grande de Chilo , 42 S) declined at a rate of about 3% per annum between 2004-2017. The population in the northern site (Isla Cha aral, 29 S) appeared roughly stable from 2006-2019, although this estimate had high uncertainty due to the small sample size in the northern site.
Publisher
IWC
Publication Year
2024
Abstract
We report progress on the analysis of capture-recapture data from two Chilean blue whale feeding grounds: a southern site in the vicinity of Isla Grande de Chilo (42 S) and a northern site from Isla Cha aral (29 S). The data consist of bilateral left and right side photo-identifications. This creates analytic challenges because some animals are likely to appear in two unreconciled capture histories, one from the left and one from the right, but the number of these double-counted individuals is unknown. We present our modelling approach and preliminary findings for feedback. We estimate that the southern population experienced a significant decline of about 3% per annum over the period from 2004?2017, whereas the northern population appeared roughly stable or even slightly increasing over a similar time period. We welcome feedback on all aspects of our analysis.