scholarly journals Observations on seals on the island of Surtsey in the period 1980-2012

2015 ◽  
Vol 13 ◽  
pp. 41-43
Author(s):  
Erlingur Hauksson

Grey seals (Halichoerus grypus Fabricius) and harbour seals (Phoca vitulina L.) have been surveyed on the coasts of Iceland since 1980. During the period 1980-2012, both seal species have declined markedly in numbers at the Icelandic coast. The grey seal has established a considerable breeding site on the northern spit of the Surtsey island. This is at present one of the biggest grey seal rookeries on the southern shores of Iceland, with estimated about 60 pups born there in the autumn of 2012. On the other hand, the harbour seal has not been numerous on Surtsey during breeding time in the summer. Breeding sites of harbour seals on the south coast of Iceland closest to Surtsey are in the estuaries of the glacial rivers Ölfusá, Þjórsá, Markarfljót and Kúðafljót. Harbour seals, however, haul-out in great numbers on the northern shores of Surtsey during the winter, presumably using the island as a resting place after foraging in the adjacent waters.

2010 ◽  
Vol 8 ◽  
pp. 143 ◽  
Author(s):  
Bjarni Mikkelsen

The harbour seal was exterminated as a breeding species in the Faroe Islands in the mid-19th Century. Historical sources document that the harbour seal used to be a common inhabitant of the sheltered fjords where breeding occurred. It was reported to be more common than the grey seal, the other pinniped specie resident around the Faroes. But the number of harbour seals seemingly decreased as human settlements and other anthropogenic activities increased. Seal hunting was apparently already introduced by the Norse that arrived on the islands in the 7th century, a hunt that finally lead to the extermination of the harbour seal. For the last 40 years the harbour seal has only been positively identified twice in the Faroe Islands, in 2001 and 2005.


1958 ◽  
Vol 15 (4) ◽  
pp. 495-516 ◽  
Author(s):  
D. M. Scott ◽  
H. D. Fisher

Identifications were made of ascarids collected from 1948 to 1956 from the stomachs of 318 harbour seals (Phoca vitulina), 812 harp seals (P. groenlandica), and 127 grey seals (Halichoerus grypus) killed in several localities along the Atlantic coast of Canada. Porrocaecum and 2 other genera of ascarids, tentatively identified as Anisakis and Contracaecum, were present in each species of seal. All 112 male Porrocaecum that were identified to species were P. decipiens.Almost all stomachs of harbour and grey seals at all seasons and in all localities contained P. decipiens. Considering all localities, the overall average incidence was about 20 adult P. decipiens in harbour seals and about 100 in grey seals.P. decipiens was normally much rarer in the stomachs of harp seals than in the other seals. It appeared most frequently in harp seals taken around the Magdalen Islands in April and May. The incidence of adult P. decipiens was much lower during the breeding season of the seals and during their southward and northward migrations within the Gulf of St. Lawrence. The incidence of P. decipiens in harp seals from the east coast of Newfoundland was very low.The relative importance of each species of seal as a vector of P. decipiens is as follows. The harbour seal is the most important in the Bay of Fundy and along the southwestern coast of Nova Scotia. Elsewhere harbour and grey seals occur in approximately equal numbers. In such localities the grey seal is probably more important than the harbour seal. The harp seal is about 100 to 200 times as numerous, while in the southwestern Gulf of St. Lawrence, as the combined populations of harbour and grey seals there. Despite this great numerical superiority the harp seal does not appear to be more important than the other seals as a host of P. decipiens.The relation between each species of seal and the incidence of larval P. decipiens in Atlantic cod (Gadus callarias) is discussed.


2020 ◽  
Vol 174 ◽  
pp. 166
Author(s):  
K. Hülskötter ◽  
S. Rohner ◽  
S. Groß ◽  
J. Lakemeyer ◽  
M. Fähndrich ◽  
...  

1990 ◽  
Vol 47 (6) ◽  
pp. 1223-1227 ◽  
Author(s):  
Morten Ryg ◽  
Christian Lydersen ◽  
Nina H. Markussen ◽  
Thomas G. Smith ◽  
Nils Are Øritsland

We have investigated the relationships between percent blubber content and xiphostemal blubber thickness or girth-to-length ratios in ringed seal (Phoca hispida), harp seal (Phoca groeniandica), and grey seal (Halichoerus grypus). The blubber content was significantly correlated with blubber depths and girth-to-length ratios in all three species, in addition, we have developed an estimator for percent blubber content (the LMD-index) based on standard length (L, in meters), body mass (M, in kilograms), and on blubber thickness (d, in meters) measured at a defined position dorsally. From these variables the percent blubber content (B%) can be estimated by the expression B% = 4.44 + 5693 [Formula: see text], with a standard error of the estimate of three percentage units. This index also gave reasonable estimates for blubber content in three harbour seals (Phoca vitulina) and eight bearded seals (Erignatus harbatus).


1983 ◽  
Vol 40 (3) ◽  
pp. 267-271 ◽  
Author(s):  
Paul Brodie ◽  
Brian Beck

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


The chief circumstance that induced Capt. Flinders to think his observations Upon the marine barometer were worthy of attention, was the coincidence that took place between the rising and falling of the mercury, and the setting in of winds that blew from the sea and from off the land, to which there seemed to be at least as much reference as to the strength of the wind or the state of the atmosphere. Our author’s examination of the coasts of New Holland and the other parts of the Terra Australis, began at Cape Leuwen, and con­tinued eastward along the south coast. His observations, which, on account of their length, we must pass over, show, that a change of wind from the northern half of the compass to any point in the southern half, caused the mercury to rise; and that a contrary change caused it to fall. Also, that the mercury stood considerably higher When the wind came from the south side of east and west, than when, in similar weather, it came from the north side.


Author(s):  
G. A. Steven

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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