Estimation of Pup Production of Hooded and Harp Seals in the Greenland Sea in 2007: Reducing Uncertainty Using Generalized Additive Models

Abstract

Øigård, T. A., T. Haug, K. T. Nilssen, and A. B. Salberg. 2010. Estimation of pup production of hooded and harp seals in the Greenland Sea in 2007: reducing uncertainty using generalized additive models. J. Northw. Atl. Fish. Sci., 42: 103-123. doi:10.2960/J.v42.m642 AbstractThe pup production of the Greenland Sea populations of hooded and harp seals were assessed in aerial surveys using two aircrafts for reconnaissance flights and photographic surveys along transects over the whelping areas from 14 March to 3 April 2007. One helicopter, operated from the applied expedition vessel, flew reconnaissance flights, monitored the distribution of seal patches and performed age-staging of the pups. The total estimate of hooded seal pup production was 16 140 (SE = 2 140, CV = 13.3%), which is similar to an estimate obtained for comparable surveys in 2005. The total pup production estimate obtained for harp seals was 110 530 (SE = 27 680, CV = 25.0%), which is slightly higher than an estimate obtained for a similar survey in 2002. The pup production and the uncertainty of the pup production estimate were estimated using a standard method for analyzing this type of survey data and a recently developed method that utilized Generalized Additive Models (GAMs). Using the two estimation methods on data from all three surveys (2002, 2005, 2007), comparable estimates of pup production were obtained. In scenarios where pups were clustered, the estimated uncertainty of the pup production estimate was much lower for the GAM method than for the conventional method. This resulted in a considerable reduction of the estimated coefficient of variation. In scenarios where pups were uniformly distributed, both methods performed the same.

Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century

“…Loss of sea ice has affected survival in some subpopulations of polar bears (Regehr et al ; Regehr et al ). Pinniped pup survival is related to the timing of sea ice breakup because young need sufficient time for suckling prior to weaning (Øigard et al ; 2013). Absence of sea ice is expected to lower Pacific walrus calf survival due to crushing at crowded haul‐out sites (Jay et al ).…”

A review of Brucella infection in marine mammals, with special emphasis on Brucella pinnipedialis in the hooded seal (Cystophora cristata)

“…This is especially important, since the Northwest Atlantic population, which has a high prevalence of B. pinnipedialis infection [30,34], has declined [131-133], and the whole hooded seal species is classified as vulnerable in the IUCN Red List of Threatened Species [136]. …”

Estimating Seal Pup Production in The Greenland Sea by Using Bayesian Hierarchical Modelling

“…() and Øigård et al . () under both a Poisson and a negative binomial likelihood, and a homogeneous Poisson model. The methods and the associated inference approaches are described below.…”

“…The whelping regions in the North Atlantic typically cover several thousand square kilometres so total pup production needs to be estimated on the basis of observations from a minor part of the region. Both the estimated total pup production and the associated uncertainty are then used as input in dynamic population models (Øigård et al ., ).…”

“…To be more informative about the non‐observed areas, we include covariate information that was extracted from satellite imagery captured on the very same date as the aerial photographic survey was conducted, to act as a proxy for ice thickness. This is important as the seal pups can be observed only on ice, with non‐observable pups accounted for within the dynamic population model (Øigård et al ., ). Compared with the other procedures our method gives larger uncertainties, especially for the harp seals.…”