Counting Weddell Seals Project Report
Degree GrantorUniversity of Canterbury
Degree LevelPostgraduate Certificate
Degree NamePostgraduate Certificate in Antarctic Studies
There is currently debate about the impacts of commercial fishery for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea upon the ecosystem as a whole and upon Weddell seals (Leptonychotes weddellii) in particular. Weddell seals lose a lot of weight during the breeding season, and the very high energy density of toothfish compared with other prey may be of critical importance to the seals as they seek to recover. However, there are many uncertainties in the analysis, both in the proportion of toothfish in the seals’ diet, and also in the number of seals in the Ross Sea ecosystem. Satellite images have been used to attempt to measure the seal population. First comparisons of satellite and ground-based counts concluded that there is a strong correlation between them (LaRue et al., 2011). Ainley et al. (2015) used satellite counts to conclude that the Weddel seal population has declined significantly between the 1960s and 2008-2012. There are, however, significant weaknesses in the existing comparison of satellite and ground-based counts. These include incomplete knowledge of the diurnal cycle in the number of seals hauling out onto the ice. The number can vary by a factor of 10 from trough to peak. In this project, approximately 20’000 images taken automatically by ground-based cameras at 10-minute intervals over three month periods in 2014 and 2015 are used to investigate the diurnal rhythms of Weddell seal haul out at Turtle Island, off Ross Island in McMurdo Sound Antarctica. The extraction of seal counts from the images will be undertaken by volunteers, working on the citizen science hosting platform Zooniverse.org. This report has been written prior to the launch of the project Weddell Seal Count on Zooniverse. The considerations in design and screenshots of the development site are presented. Data from the PCAS 2014-15 “sealathon” are used to illustrate how the results from Weddell Seal Count will be analysed.