Using satellite telemetry and aerial counts to estimate space use by grey seals around the British Isles

Abstract

Summary1. In the UK, resolving conflicts between the conservation of grey seals, the management of fish stocks and marine exploitation requires knowledge of the seals' use of space. We present a map of grey seal usage around the British Isles based on satellite telemetry data from adult animals and haul-out survey data. 2. Our approach combined modelling and interpolation. To model the seals' association with particular coastal sites (the haul-outs), we divided the population into subpopulations associated with 24 haul-out groups. Haul-out-specific maps of accessibility were used to supervise usage estimation from satellite telemetry. The mean and variance of seal numbers at each haul-out group were obtained from haul-out counts. The aggregate map of usage for the entire population was produced by adding together the haulout-specific usage maps, weighted by mean number of animals using that haul-out. 3. Seal usage was primarily concentrated (i) off the northern coasts of the British Isles, (ii) closer to the coast than might be expected purely on the basis of accessibility from the haul-outs and (iii) in a limited number of marine hot-spots. 4. Although our results currently represent the best estimate of how grey seals use the marine environment around Britain, they are neither definitive nor equally precise for all haul-outs. Further data collection should focus in the south-west of the British isles and aerial counts should be repeated for all haul-outs. Synthesis and applications.This work provides environmental managers with current estimates of grey seal usage and describes a methodology for maximizing data efficiency. Our results could guide government departments in licensing marine exploitation by the oil industry, in estimating grey seal predation pressure on vulnerable or economically important prey and in delineating marine special areas of conservation (SAC). Our finding that grey seal usage is characterized by a limited number of hot-spots means that the species is particularly suited to localized conservation efforts.

Flow simulation along a seal: the impact of an external device

“…Block 2005;Kooyman 2004;Naito 2004;Ponganis 2007) and satellite transmitters (e.g. Culik and Luna-Jorquera 1997;Matthiopoulos et al 2004;Myers et al 2006), have been used on various animal species to investigate a wide range of ecological and conservation questions. These include systems to study physiology (such as body temperature), behaviour (such as diving and foraging behaviour) and use of the ecosystem (such as seasonal and diurnal migrations).…”

“…Gifford et al 2007;Read and Westgate 1997), seals (e.g. Call et al 2007;Matthiopoulos et al 2004), marine turtles (e.g. Lohmann et al 2008;Watson and Granger 1998), penguins (e.g.…”

The status of the harbour seal (<i>Phoca vitulina</i>) in Ireland

“…The fine-scale information resulting from the at-sea behaviour of the seals provides a means of identifying foraging areas offshore. Extending tagging efforts to other significant haulout sites on other parts of the Irish coast and modelling the telemetry and population data using recent techniques (Matthiopoulos et al 2004) will contribute to spatially explicit population foraging distribution information.…”

“…Research on harbour seal diet in Ireland has been limited to studies conducted in County Down, Northern Ireland in the late 1990s ), in Galway Bay in western Ireland 2001-2004 and in Bantry Bay and the Kenmare River in southwest Ireland since 2006 , Kavanagh, 2008. The studies suggest that harbour seals are opportunistic feeders as a wide variety of prey species was found in the diet of seals on both the west and southwest coasts, including 16 teleost species and two species of cephalopods, and there was evidence of seasonal and geographical variation in the diet.…”

“…The fine-scale information resulting from the at-sea behaviour of the seals provides a means of identifying foraging areas offshore. Extending tagging efforts to other significant haulout sites on other parts of the Irish coast and modelling the telemetry and population data using recent techniques (Matthiopoulos et al 2004) will contribute to spatially explicit population foraging distribution information.Research on harbour seal diet in Ireland has been limited to studies conducted in County Down, Northern Ireland in the late 1990s ), in Galway Bay in western Ireland 2001-2004 and in Bantry Bay and the Kenmare River in southwest Ireland since 2006, Kavanagh, 2008. The studies suggest that harbour seals are opportunistic feeders as a wide variety of prey species was found in the diet of seals on both the west and southwest coasts, including 16 teleost species and two species of cephalopods, and there was evidence of seasonal and geographical variation in the diet.…”