scholarly journals British grey seal (Halichoerus grypus) abundance in 2008: an assessment based on aerial counts and satellite telemetry

2011 ◽  
Vol 68 (10) ◽  
pp. 2201-2209 ◽  
Author(s):  
Mike Lonergan ◽  
Callan D. Duck ◽  
Dave Thompson ◽  
Simon Moss ◽  
Bernie McConnell
Keyword(s):  
East Coast ◽  
Satellite Telemetry ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Total Size ◽  
Aerial Surveys ◽  
Seal Population ◽  
Pup Survival ◽  
Age Structured ◽  
Electronic Tags

Abstract Lonergan, M., Duck, C. D., Thompson, D., Moss, S., and McConnell, B. 2011. British grey seal (Halichoerus grypus) abundance in 2008: an assessment based on aerial counts and satellite telemetry. – ICES Journal of Marine Science, 68: 2201–2209. Recent estimates of the total size of the British grey seal population have been based on fitting age-structured models to estimates of pup production. The estimates were sensitive to whether density-dependence was considered to act on fecundity or pup survival. This study provides an alternative estimate for abundance in 2008: 91 800 animals (95% confidence interval, CI, 78 400–109 900). The estimate is consistent with the results of existing models where population density influences pup survival. It suggests that reductions in fecundity are unlikely to have been the cause of the recent slowing of the rate of growth of the population. The estimate presented is based on aerial surveys of the entire Scottish coast and the east coast of England. The surveys were carried out in August of 2007–2009 and restricted to the 2 h each side of daylight low water. Data from 107 electronic tags deployed between 1995 and 2008 were used to estimate the proportion of animals hauled out during the surveys. Overall, the animals hauled out for 31% (95% CI 15–50%) of the survey windows. No significant effects on the proportion of animals hauled out were detected from year, location, age, sex, temperature, rainfall, or the timing of low tide.

Pup production and population trends of the grey seal (Halichoerus grypus) in the Gulf of St. Lawrence

1998 ◽  
Vol 55 (2) ◽  
pp. 423-430 ◽  
Author(s):  
M O Hammill ◽  
G B Stenson ◽  
R A Myers ◽  
W T Stobo
Keyword(s):  
Population Trends ◽  
Annual Rate ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Northwest Atlantic ◽  
Mark Recapture ◽  
Seal Population ◽  
Independent Estimate ◽  
Anticosti Island

Grey seal (Halichoerus grypus) pup production of the Gulf of St. Lawrence component of the Northwest Atlantic grey seal population was determined for the 1984-1986 and 1989-1990 periods using mark-recapture methods. Pup production estimates based on recaptures from shot samples from Anticosti Island ranged from 5436 (SE = 672) to 6955 (SE = 1183) for 1984-1986. An independent estimate for 1984-1986, based on animals captured on Sable Island, was 7431 (SE = 1414) to 8633 (SE = 2827). Mark-recapture estimates of pup production for 1989 and 1990 from shot samples collected from Anticosti Island were 8825 (SE = 3164) and 9156 (SE = 2652), respectively. The estimates based on animals captured on Sable Island varied from 7295 (SE = 2118) to 8116 (SE = 846) for 1989-1990. Both the Anticosti Island and Sable Island recovery samples underestimate 1989 pup production due to hunting which removed 1612 pups from the population before they could disperse. The Gulf component of the Northwest Atlantic grey seal population is increasing at an annual rate of 7.4% (SE = 2.2).

Patterns of parental relatedness and pup survival in the grey seal (Halichoerus grypus)

2004 ◽  
Vol 13 (8) ◽  
pp. 2365-2370 ◽  
Author(s):  
K. BEAN ◽  
W. AMOS ◽  
P. P. POMEROY ◽  
S. D. TWISS ◽  
T. N. COULSON ◽  
...  
Keyword(s):  
Halichoerus Grypus ◽  
Grey Seal ◽  
Pup Survival

scholarly journals Modelling the abundance of grey seals (Halichoerus grypus) along the Norwegian coast

2012 ◽  
Vol 69 (8) ◽  
pp. 1436-1447 ◽  
Author(s):  
Tor Arne Øigård ◽  
Anne Kirstine Frie ◽  
Kjell Tormod Nilssen ◽  
Mike Osborne Hammill
Keyword(s):  
Confidence Interval ◽  
Population Size ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Norwegian Coast ◽  
Structured Population ◽  
Population Dynamics Model ◽  
Level Model ◽  
Age Structured ◽  
The Uk

Abstract Øigård, T. A., Frie, A. K., Nilssen, K. T., and Hammill, M. O. 2012. Modelling the abundance of grey seals (Halichoerus grypus) along the Norwegian coast. – ICES Journal of Marine Science, 69: . An age-structured population dynamics model of the Norwegian grey seal (Halichoerus grypus) population has been developed. The model is of a Bayesian character in the sense that priors for various parameters were used. Model runs indicated an increase in the abundance of the total Norwegian grey seal population during the last 30 years, suggesting a total of 8740 (95% confidence interval: 7320–10 170) animals in 2011. A total catch of 707 (95% confidence interval: 532–882) grey seals would maintain the population size at the 2011 level. Model runs suggest that current catch levels will likely result in a reduction in the population size in Sør-Trøndelag and Nord-Trøndelag counties, and an increase in the population size in Rogaland, Nordland, Troms, and Finnmark counties. The model runs assumed that 80% of the seals taken in Rogaland came from the UK and that 50 and 55% of the catches in Troms and Finnmark, respectively, were immigrants from Russia.

scholarly journals Abundance of grey seals in Icelandic waters, based on trends of pup-counts from aerial surveys

2007 ◽  
Vol 6 ◽  
pp. 85 ◽  
Author(s):  
Erlingur Hauksson
Keyword(s):  
Halichoerus Grypus ◽  
Breeding Period ◽  
Grey Seal ◽  
The West ◽  
Breeding Sites ◽  
The North ◽  
Aerial Surveys ◽  
Breeding Distribution ◽  
The 1960S ◽  
Icelandic Waters

Grey seals (Halichoerus grypus Fabricius, 1791) are distributed all around the Icelandic coast. The majority of the population breeds on the west- and northwest shores, with a second high density in the breeding distribution on the southeast coast of Iceland. During the last 5 decades the Icelandic grey seals have dispersed from the west- to the northwest-, the north- and the northeast-coast. The breeding period occurs from the middle of September to early November, with a maximum in mid October. The time of peak pupping shows some variation, beginning earlier along the west coast and later in the north and southeast. Seven aerial surveys to estimate pup production in Iceland were flown during October to November during the period from 1980 to 2004. Pup counts of the Icelandic grey seal, at all breeding sites combined, have been decreasing annually by about 3% (±1% s.e.), during the period 1982-2002. During the period 1990-2002, this downward trend doubled to about 6% annually. The abundance of the grey seal around Iceland in the year 2002 was estimated to be 4,100 to 5,900 animals. This is higher than estimates of around 2,000 animals during the 1960s, but much less than the estimated population of 8,000 to 11,500 in 1982.

Utilizing next-generation sequencing to identify prey DNA in western North Atlantic grey seal Halichoerus grypus diet

2020 ◽  
Vol 655 ◽  
pp. 227-240
Author(s):  
KR Flanders ◽  
ZH Olson ◽  
KA Ono
Keyword(s):  
Next Generation Sequencing ◽  
Feeding Habits ◽  
Atlantic Menhaden ◽  
Halichoerus Grypus ◽  
Frequency Of Occurrence ◽  
Grey Seal ◽  
Next Generation ◽  
Significant Difference ◽  
Generation Sequencing ◽  
Seal Diet

Increasing grey seal Halichoerus grypus abundance in coastal New England is leading to social, political, economic, and ecological controversies. Central to these issues is the foraging ecology and diet composition of the seals. We studied grey seal feeding habits through next-generation sequencing of prey DNA using 16S amplicons from seal scat (n = 74) collected from a breeding colony on Monomoy Island in Massachusetts, USA, and report frequency of occurrence and relative read abundance. We also assigned seal sex to scat samples using a revised PCR assay. In contrast to current understanding of grey seal diet from hard parts and fatty acid analysis, we found no significant difference between male and female diet measured by alpha and beta diversity. Overall, we detected 24 prey groups, 18 of which resolved to species. Sand lance Ammodytes spp. were the most frequently consumed prey group, with a frequency of occurrence (FO) of 97.3%, consistent with previous studies, but Atlantic menhaden Brevoortia tyrannus, the second most frequently consumed species (FO = 60.8%), has not previously been documented in US grey seal diet. Our results suggest that a metabarcoding approach to seal food habits can yield important new ecological insights, but that traditional hard parts analysis does not underestimate consumption of Atlantic cod Gadus morhua (FO = 6.7%, Gadidae spp.) and salmon Salmo salar (FO = 0%), 2 particularly valuable species of concern.

Predation by Sharks on the Grey Seal (Halichoerus grypus) in Eastern Canada

1983 ◽  
Vol 40 (3) ◽  
pp. 267-271 ◽  
Author(s):  
Paul Brodie ◽  
Brian Beck
Keyword(s):  
Key Words ◽  
Population Size ◽  
Halichoerus Grypus ◽  
Longline Fishery ◽  
Grey Seal ◽  
Eastern Canada ◽  
The Past ◽  
Harbour Seals ◽  
Commercially Important ◽  
Important Fish

The increase in population size of the grey seal (Halichoerus grypus) off eastern Canada over the past 20 yr may be attributed to a decrease in shark stocks, their supposed predators. Reduction of the shark population is presumed to have resulted from a directed longline fishery and, of greater significance, from a change in the fishery for swordfish (Xiphias gladius) from selective harpooning to pelagic longlining, which has produced a large bycatch of sharks. The resulting enhanced survival of grey seals is reflected in greater infestation of commercially important fish species by the codworm (Phocanema decipiens).Key words: grey seals, harbour seals, sharks, swordfish, codworm, predation, fisheries

scholarly journals Does predation by grey seals (Halichoerus grypus) affect Bothnian Sea herring stock estimates?

2012 ◽  
Vol 69 (8) ◽  
pp. 1448-1456 ◽  
Author(s):  
Anna Gårdmark ◽  
Örjan Östman ◽  
Anders Nielsen ◽  
Karl Lundström ◽  
Olle Karlsson ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Older Individuals ◽  
Standard Assessment ◽  
Abundance Estimates ◽  
Stock Biomass ◽  
Key Species ◽  
Spawning Stock ◽  
Bothnian Sea

Abstract Gårdmark, A., Östman, Ö., Nielsen, A., Lundström K., Karlsson O., Pönni, J., and Aho, T. 2012. Does predation by grey seals (Halichoerus grypus) affect Bothnian Sea herring stock estimates? – ICES Journal of Marine Science, 69: . Mortality of small pelagic fish due to marine mammals is generally considered to be low compared with other sources of mortality. With recent recoveries of marine mammal predators worldwide, this may no longer hold. The grey seal (Halichoerus grypus) population in the Bothnian Sea has increased fivefold since 1985. Its main prey, herring (Clupea harrengus), is a key species for fisheries in the region. Yet, current stock assessments assume constant natural mortality, leading to a risk of biased stock estimates with increasing predation and misleading analyses of herring population dynamics. We estimated grey seal predation from diet data and reanalysed herring spawning stock biomass (SSB) during 1973–2009. Accounting for predation increased the herring SSB 16% (maximum 19%), but this was within the confidence intervals when ignoring predation. Although mortality in older individuals was inflated when accounting for seal predation, this did not change the conclusions about drivers of herring dynamics. Accounting for grey seal predation is important for abundance estimates of old herring, but currently not for SSB estimates, given the great uncertainties in the standard assessment. The grey seal impact on Bothnian Sea herring will need to be reassessed if stock age composition, grey seal feeding preferences, or total stock development change.

scholarly journals Estimates of the size of the Baltic grey seal population based on photo-identification data

2007 ◽  
Vol 6 ◽  
pp. 163 ◽  
Author(s):  
Lex Hiby ◽  
Torkel Lundberg ◽  
Olle Karlsson ◽  
John Watkins ◽  
Mart Jüssi ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Population Based ◽  
Point Estimate ◽  
Grey Seal ◽  
The Baltic Sea ◽  
Photo Identification ◽  
A Value ◽  
Seal Population ◽  
The Baltic ◽  
Year 2000

The size of the year 2000 summer population of grey seals in the Baltic Sea was estimated using identification of individual seals from photographs taken over a period of 6 years. Photos were taken at haul-out sites within all major grey seal areas in the semi-closed Baltic Sea. The point estimate is 15,631, based on a value for annual survival of identification markings of 0.904, which was also estimated using the photo-id data, with 95% confidence limits from 9,592 to 19,005. The estimate is subject to an unknown, but probably small, upward bias resulting from the risk of failure to identify all individuals in the photographs used for the analysis. An estimated minimum of 15,950 seals were counted at moulting haul-outs in 2003, which thus provides a lower bound on the population size in that year and represents 80% of the photo-id point estimate.

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