An estimate of the size of the British grey seal population based on summer haulout counts and telemetry data

Open Access Report 2011

Special Committee on Seals

We fitted a Bayesian state-space model of British grey seal population dynamics to two sources of data: (1) regional estimates of pup production from 1984 to 2012, and (2) an independent estimate assumed to be of total population size just before the 2008 breeding season. The model allowed for density dependence in pup survival, using a flexible form for the density dependence function, and assumed no movement of recruiting females between regions. This model is identical to that used to provide last year’s advice, and the same “revised” priors were used, including a prior on adult sex ratio. One small change in data was that the total population size estimate was adjusted to account for the fact that the population model is based only on regularly monitored breeding colonies (approx. 94% of the total population). We used the model to predict past the last data point (2012) to give estimates of population size in 2014. Estimated adult population size in 2014 was 95,200 (95% CI 76,400-127,500). The model assumes constant adult (i.e., aged 6+) female survival. The prior distribution has support in the range (0.8, 1.0) with a prior mean of 0.91 (SD 0.05); the posterior mean is an implausibly high 0.99 (SD 0.01). We investigated the effect of constraining the prior to the range (0.8, 0.97). Posterior mean adult survival with this revised prior was 0.95 (SD 0.03); estimated population size with this revised prior was 105,200 (95% CI 87,000-128,800). Female survival is currently assumed to be the same for all ages. We investigated the possible effect of including survival senescence, and concluded that adding it would make no practical difference to the modelled population dynamics. Sex ratio is an important parameter in the model, scaling estimates of adult female population size from the population dynamics model to total population size. The current prior is highly informative (prior mean on ratio of total population:adult females 1.7 SD 0.02). We investigated the consequences of using a less informative prior suggested in a previous briefing paper (prior mean 1.2 SD 0.63). With this prior (and the revised prior on adult female survival), total population size was estimated to be much lower (88,600 with 95%CI 70,200-111,700), but the ratio of total population:adult females was an implausibly low 1.14 (SD 0.09).

Link To Publication

Keywords: SCOS

Similar Research

Anthropogenic sound and marine mammal health: measures of the nervous and immune systems before and after intense sound exposure

Pay-walled Journal Article 2004

Canadian Journal of Fisheries and Aquatic Sciences

Anthropogenic sound is a potential stressor for marine mammals that may affect health, as has been demonstrated in other mammals. Therefore, we have initiated investigations on...
Read More

International Regulation Of Transboundary Pollutants: The Emerging Challenge Of Ocean Noise

Open Access Journal Article 2001

Ocena and Coastal Law Journal

Transboundary pollution law poses the challenge of addressing environmental problems irrespective of boundaries in an international legal system that values, above all, territorial sovereignty of individual...
Read More

A Brief Review of Anthropogenic Sound in the Oceans

Open Access Journal Article 2007

International Journal of Comparative Psychology

Sound in the oceans is generated by a variety of natural sources, such as breaking waves, rain, and marine animals, as well as a variety of...
Read More

Effect of anthropogenic low-frequency noise on the foraging ecology of Balaenoptera whales

Pay-walled Journal Article 2006

Animal Conservation

The human contribution to ambient noise in the ocean has increased over the past 50 years, and is dominated by low-frequency (LF) sound (frequencies <1000 Hz)...
Read More

Response and Responsibility: Regulating Noise Pollution in the Marine Environment

Pay-walled Journal Article 2007

Journal of International Wildlife Law and Policy

The ocean is becoming an increasingly noisy environment. With a rise in com-mercial shipping, resource extraction activities, and military-related activities,the underwater ocean environment is a virtual...
Read More

Influences of man-made noise and other human actions on cetacean behaviour

Pay-walled Journal Article 1995

Marine and Freshwater Behaviour and Physiology

Behavioral reactions of cetaceans to man-made noises are highly variable, ranging from attraction (e.g. bow riding by dolphins) or no response through short-term changes in behaviour...
Read More

Determination of environmental sensitivity of acoustic propagation on continental shelves using an equivalent fluid parabolic equation model

Pay-walled Journal Article 1995

The Journal of the Acoustical Society of America

A coupled environment and acoustic prediction system was developed to evaluate the sensitivity of acoustic propagation on the continental shelf to water column and sediment properties....
Read More

Effects of underwater noise on auditory sensitivity of a cyprinid fish

Pay-walled Journal Article 2001

Hearing Research

The ability of a fish to interpret acoustic information in its environment is crucial for its survival. Thus, it is important to understand how underwater noise...
Read More

Effects of noise exposure on click detection and the temporal resolution ability of the goldfish auditory system

Pay-walled Journal Article 2005

Hearing Research

Hearing specialist fishes investigated so far revealed excellent temporal resolution abilities, enabling them to accurately process temporal patterns of sounds. Because noise is a growing environmental...
Read More

The effects of noise on the auditory sensitivity of the bluegill sunfish, Lepomis macrochirus

Pay-walled Journal Article 2002

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

As concerns about the effects of underwater anthropogenic noises on the auditory function of organisms increases, it is imperative to assess if all organisms are equally...
Read More