Further studies on grey seal (Halichoerus grypus) pup mortality on North Rona

1988 ◽  
Vol 144 (5) ◽  
pp. 497-506 ◽  
Author(s):  
J.R. Baker
Keyword(s):  
Halichoerus Grypus ◽  
Grey Seal ◽  
Pup Mortality

scholarly journals Status of grey seals (Halichoerus grypus) in Norway

2007 ◽  
Vol 6 ◽  
pp. 23 ◽  
Author(s):  
Kjell Tormod Nilssen ◽  
Tore Haug
Keyword(s):  
Total Population ◽  
Halichoerus Grypus ◽  
Population Estimates ◽  
Grey Seal ◽  
Breeding Area ◽  
Breeding Sites ◽  
Norwegian Coast ◽  
The North ◽  
Minimum Estimate ◽  
Pup Mortality

During the period September-December in 2001-2003, ship based surveys of grey seal (Halichoerus grypus) pups, including tagging, counting and staging of pups, were conducted along the Norwegian coast. All known and other potential breeding areas were surveyed from Rogaland county in the south to Finnmark county in the north. Most of the breeding sites were surveyed only once, but some sites were surveyed 2-4 times. The investigations resulted in a total minimum estimate of 1,159 grey seal pups born in Norwegian waters. Nordland county was the most important breeding area where about 50% of the pups were born. Total population estimates were derived from the recorded number of pups born using a range of multipliers (4.0-4.7), based on observed annual growth rates of approximately 7-12% in other grey seal populations. This gave a total estimate of about 5,800-6,600 grey seals including pups in Norwegian waters. However, the total pup production was probably underestimated due to only one pup count in most of the breeding sites. Observed mean pup mortality was 1.1% during the breeding season along the Norwegian coast.

scholarly journals Grey seals on the Murman coast, Russia: status and present knowledge

2007 ◽  
Vol 6 ◽  
pp. 13 ◽  
Author(s):  
Sergej V Ziryanov ◽  
Vasily L Mishin
Keyword(s):  
Nature Reserve ◽  
White Sea ◽  
Present Knowledge ◽  
Seasonal Distribution ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
The White Sea ◽  
Breeding Sites ◽  
Murmansk Region ◽  
Pup Mortality

Grey seals (Halichoerus grypus) are distributed along the entire northern Murman coast in Russia. Breeding sites are located mainly on the Ainov and Seven islands, which belong to the Kandalaksha Nature Reserve. The annual pup production was estimated to be around 800 pups in the early 1990s, and the pup mortality has been observed to be relatively high. The population was estimated to be approximately 3,500 individuals in 1994. Grey seals migrate in small numbers into the White Sea during summer. The grey seal is protected and registered in the Red Books of Russia, Murmansk region and Fennoscandia. The main results of grey seals investigations from 1986 to 2000 are briefly reviewed. There are no recent studies on abundance, seasonal distribution, growth, moulting and feeding of the species.

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 A Short Investigation into the Habits, Abundance, and Species of Seals on the North Cornwall Coast

1934 ◽  
Vol 19 (2) ◽  
pp. 189-501 ◽  
Author(s):  
G. A. Steven
Keyword(s):  
Relative Abundance ◽  
Direct Evidence ◽  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
The North ◽  
Single Night ◽  
Considerable Size

1. In the course of three trips to the herring grounds in the vicinity of St. Ives five seals were sighted. Seven others were also seen at various other times and places in the course of five days spent in that locality.2. During a single night at sea in Port Isaac Bay eight seals were sighted.3. It was obvious from the movements of certain of the seals observed on the fishing grounds that they were attracted to the herring nets.4. Direct evidence that the seals actually remove fish from the nets was not obtained.5. Damage done to drift nets by seals is negligible.6. Grey Seals (Halichœrus grypus) are present in considerable numbers, and are probably the commonest seals in Cornish waters.7. Brown Seals (Phoca vitulina) appear to be few—they may even be rare—around Cornwall.8. There is at least one seal colony of considerable size in certain caves near Boscastle. This appears to consist of Grey Seals. Probably other such colonies exist on the Cornish coast.9. Clupeoid remains have been found in two out of the three Grey Seal stomachs which have been examined.10. Further and more exact knowledge of the habits and relative abundance of Grey and Brown Seals around the Cornish coast is desirable.

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