Series: Toktrapport 2022 - 7
Cruise no.: 2022703 :
The 2022 survey of harp and hooded seal pup production in the Greenland Sea was carried out to obtain updated estimates to be used to assess current status of these two seal stocks. Since a similar survey in 2018 indicated a 40% reduction in harp seal pup production since the 2012 survey, and the continued lack of increase in pup production of the severely depleted hooded seal stock despite its protection from hunting since 2007, a new survey after a period of only 4 years was urgent. The survey was carried out using well established methodologies for these species, including 1) reconnaissance of the drift ice breeding habitat from a helicopter based on the research icebreaker R/V Kronprins Haakon and a fixed-wing aircraft stationed at Constable Pynt in East Greenland, 2) deploying GPS beacons around the identified breeding areas to monitor its displacement in the East Greenland Current, 3) carrying out staging surveys to monitor the pup age structure and estimate the optimal day of pup counting as well as correction factors accounting for pups not present on the ice at the time of counting, and 4) conducting aerial photographic surveys using the fixed-wing aircraft. Ice conditions in the Greenland Sea were similar as those experienced in 2018, with a relatively narrow band of pack ice over the shelf break near the coast of East Greenland. Seal whelping patches were initially discovered on March 21 & 22nd, within an area stretching from 72°53’N / 16°42’W in the north to 71°51’N / 17°30’W in the south. Five GPS beacons were deployed at the main whelping patches within this area, allowing us to track the continuous drift due to strong northerly winds during the period between initial reconnaissance and the final pup counting. Pup staging surveys were carried out on March 22nd, 23rd, 25th, 28th and 30th, providing us with a solid dataset with which to assess the development of pup age dynamics, determine the optimal day for photographic surveys, and to estimate correction factors to account for pups absent from the ice during the photographic surveys. The final photographic surveys were carried out on March 28th in a relatively narrow (20-30 nm) N/S band stretching from 71°00’N / 20°00’W in the NE to 69°34’N / 20°36’W in the SW. In total, 2,463 images were obtained during the aerial photographic survey, and following pre-processing (georeferencing and ortorectification), these will be analysed both manually and using dedicated machine learning systems, to determine the number of pups present in images. Results will be used to estimate the total 2022 pup production for each species and will also be combined with estimates from previous years to estimate the population sizes using the dedicated population dynamics model. The entire updated dataset will be made available to the upcoming ICES benchmarking meeting for harp and hooded seal population modelling, and results will finally be evaluated at the upcoming meeting of the ICES WGHARP working group in 2023.