ESTIMATING PUP PRODUCTION OF HARP SEALS, PAGOPHILUS GROENLANDICUS, IN THE NORTHWEST ATLANTIC

Abstract

Photographic and visual aerial surveys to determine current pup production of Northwest Atlantic harp seals were conducted off Newfoundland and in the Gulf of St. Lawrence during March 1999‐Photographic surveys were conducted on all whelping concentrations between 14 and 24 March, whereas a visual survey was made of the southern Gulf concentrations on 14 March. Pup production was estimated to be 739,100 (SE = 96,300, CV = 13.0%) at the Front, 82,600 (SE = 22,500, CV = 27.2%) in the northern Gulf, and 176,200 (SE = 25,400, CV = 14.4%) in the southern Gulf (Magdalen Island) for a total of 997,900 (SE = 102,100, 10.2%). Changes in aerial survey estimates indicate that pup production has increased since 1994. A new method to correct for the temporal change in the proportion of pups present on the ice was examined by fitting the percentage of pups observed in three age‐dependent stages to a Normal distribution. The results were compared to those obtained from a more complex model used previously. The Simple model produced slightly higher, and hence more conservative, estimates of the proportion of births that had occurred before the time of the survey than the Complex model. When using the Simple model fewer assumptions regarding the start date of pupping and the proportion of older pups remaining on the ice were required, the herd had to be followed for a shorter period, and a more convenient means of calculating confidence limits was available.

Geographic variation in vocalizations of pups and mother-pup behavior of harp seals Pagophilus groenlandicus

“…1). These were referred to as the Cartwright and Belle Isle concentrations, respectively, by Stenson et al (2005). The estimate of the number of pups in patch GS-A was 4700 and in patch GS-B was 82 600 (Haug et al 2006); the estimate in patch F-A was 368 705 and in patch F-B was 272 074 pups (Stenson et al 2005).…”

“…Data collection for the Greenland Sea and the Front were carried out in conjunction with harp seal abundance surveys run by the Institute of Marine Research in Norway and the Department of Fisheries and Oceans in Canada (see Haug et al 2006 andStenson et al 2005 for descriptions of the surveys). Once breeding aggre-gations were located, data collection on mothers and pups was carried out from ice-strengthened vessels either directly or as a base for helicopters.…”

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

“…We have chosen to use the term "conventional survey analysis" for the standard method of analyzing such survey data. This does not mean that this method is the conventional way of analyzing any type of strip transect count data, but rather refers to that this has been the standard method used for analyzing strip transect count data of pups on ice and used in Hammil et al (1992), Stenson et al (1993Stenson et al ( , 1997Stenson et al ( , 2002Stenson et al ( , 2003Stenson et al ( , 2006, Haug et al (2006), Salberg et al (2008), and Potelov et al (2003). The term "conventional survey analysis" refers both to the actual pup production estimator and the method for estimating the uncertainty of the pup production estimate.…”

“…To extrapolate the counted number of pups on the strips to the number of pups in the whole patch, a conversion factor determined by dividing the transect interval by the transect width is used. This method does not take into account spatial seal density variability along transects, but extrapolates the mean density along a transect to areas between the transects (e.g., Stenson et al, 2003). According to Salberg et al, (2009), the underlying assumption behind the classical way of estimating the variance for this type of surveys is equal mean values between two neighboring transects.…”

“…There are uncertainties in the assumptions required when estimating seal abundance from catch-at-age data, sequential population models, and mark-recapture data. For this reason, independent estimates of pup production, using aerial photography or visually based strip transect methods, have been recommended and used to determine abundance of both harp and hooded seals in their whelping areas in the northwest Atlantic (Bowen et al, 1987;Hammill et al, 1992;Stenson et al, 1993Stenson et al, , 1997Stenson et al, , 2002Stenson et al, , 2003Stenson et al, , 2006, in the Greenland Sea Haug et al, 2006;Salberg et al, 2008) and in the White Sea (Potelov et al, 2003;ICES, 2008). The status of the stocks are subsequently assessed by fitting population models to the independent estimates of pup production (e.g., Healey and Stenson, 2000;ICES, 2006aICES, , 2008Hammill and Stenson, 2005Skaug et al, 2007).…”