Assessment pup production in the harp seal population of the White Sea in 2023 and 2024

The aim of the research to assess the pup production in the harp seal population in the White Sea in 2023 and 2024.

Methods. An aerial survey of marine mammals to assess the abundance of pups and adults of the White Sea harp seal population using unmanned aerial vehicles/drones (UAVs) was conducted over the areas of drifting ice in the White Sea. A multispectral technique was applied which consisted in simultaneous photographing of the sea surface done with a high-resolution photo-camera and an infrared (IR) camera. Aerial survey data (synchronized pairs of photo- and IR-images) were processed using the «Python» neural network with the «Yolo v4» module. An assessment of harp seal pup production was carried out using the method of discrete extrapolation. The harp seal population was calculated using cohort analysis takin into account of mortality by years.

Novelty. Full-scale multispectral aerial survey using several UAVs simultaneously. Automatic processing of huge amounts of digital photographs in optical and infrared ranges using computer vision technologies to find and recognize animals in photographs.

Result. The 2024 data provided a total number of the White Sea harp seal population of 141692 + 8696 newborn pups and a total harp seal population estimate of 1548840 individuals. The 2023 assessment pup production was lower and was estimated at 124645 + 20774 individuals. The distribution of harp seal pups on the drifting ice of the White Sea in the winter-spring period is determined mainly by the ice conditions and wind conditions. Interannual fluctuations in the number of harp seal pups are determined by the number of mature females participating in reproduction.

Practical significance: the data obtained will be used to assess the size of the White Sea population of harp seals and to develop recommendations for its conservation and rational use.

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