scholarly journals Increasing numbers of harbour seals and grey seals in the Solent

2021 ◽  
Author(s):  
Robyne Castles ◽  
Fiona Woods ◽  
Peter Hughes ◽  
John Arnott ◽  
Louise MacCallum ◽  
...  
Keyword(s):  
Harbour Seals

Diet mixing in an aquatic carnivore, the harbour seal

2005 ◽  
Vol 83 (6) ◽  
pp. 851-859 ◽  
Author(s):  
Stephen J Trumble ◽  
Michael A Castellini
Keyword(s):  
Dry Matter ◽  
Single Species ◽  
Pacific Herring ◽  
Mixed Diet ◽  
Feeding Frequency ◽  
Digestible Energy ◽  
Diet Mixing ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Harbour Seals ◽  
The Mean

To determine the effects of diet mixing on digestive performance, harbour seals (Phoca vitulina L., 1758) were offered either pure diets of Pacific herring (Clupea pallasii Valenciennes, 1847) or walleye pollock (Theragra chalcogramma (Pallas, 1814)) or a 1:1 mix of herring and pollock. Regardless of diet, retention time decreased approximately 40% as intake quadrupled. The mean apparent digestible dry matter (ADDM) was greatest on mixed diets during low feeding frequency trials; ADDM during high feeding frequency trials was significantly reduced as intake increased for animals on the single-species (pollock or herring) diets. As intake increased, up to 45% more digestible energy was assimilated from the mixed diet than from either single-species diet. The findings of this study suggest that a mixed diet consisting of prey differing in lipid and protein amounts increased digestible energy intake in harbour seals. Our measures of intake and ADDM in harbour seals revealed digestive flexibility and indicated that digestion in harbour seals was more efficient on a mixed diet.

The influence of underwater data transmission sounds on the displacement behaviour of captive harbour seals (Phoca vitulina)

2006 ◽  
Vol 61 (1) ◽  
pp. 19-39 ◽  
Author(s):  
Ronald A. Kastelein ◽  
Sander van der Heul ◽  
Willem C. Verboom ◽  
Rob J.V. Triesscheijn ◽  
Nancy V. Jennings
Keyword(s):  
Data Transmission ◽  
Phoca Vitulina ◽  
Harbour Seals

scholarly journals Lungworm seroprevalence in free-ranging harbour seals and molecular characterisation of marine mammal MSP

2016 ◽  
Vol 5 (1) ◽  
pp. 48-55 ◽  
Author(s):  
Sophia Arlena Ulrich ◽  
Kristina Lehnert ◽  
Ana Rubio-Garcia ◽  
Guillermo J. Sanchez-Contreras ◽  
Christina Strube ◽  
...  
Keyword(s):  
Marine Mammal ◽  
Molecular Characterisation ◽  
Harbour Seals ◽  
Free Ranging

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

Ambient temperature does not affect the tactile sensitivity of mystacial vibrissae in harbour seals.

1998 ◽  
Vol 201 (22) ◽  
pp. 3023-3029 ◽  
Author(s):  
G Dehnhardt ◽  
B Mauck ◽  
H Hyvärinen
Keyword(s):  
Ambient Temperature ◽  
Thermal Emission ◽  
Normal Skin ◽  
Cold Season ◽  
Cooling Power ◽  
Difference Threshold ◽  
Tactile Sensitivity ◽  
Camera System ◽  
Width Difference ◽  
Harbour Seals

Vibrissae provide pinnipeds with tactile information primarily in the aquatic environment, which is characterized by its high thermal conductivity and large potential cooling power. Since studies of thermal effects on human tactile sensitivity have revealed that cooling below normal skin temperature impairs sensitivity, the present study investigates the tactile sensitivity of the vibrissal system of harbour seals at varying ambient temperatures. Using plates bearing gratings of alternating grooves and ridges, the texture difference thresholds of two adult seals were determined under water. We took advantage of the natural difference in ambient temperature between summer and winter. Mean water temperature was 1. 2 degreesC during the winter and 22 degreesC during the summer. During the cold season, the thermal status of both seals was examined using an infrared-sensitive camera system. The texture difference threshold of both seals remained the same (0.18 mm groove width difference) under both test conditions. The thermographic examination revealed that the skin areas of the head where the mystacial and supraorbital vibrissae are located show a substantially higher degree of thermal emission than do adjacent skin areas. This suggests that, in the vibrissal follicles of harbour seals, no vasoconstriction occurs during cold acclimation, so that the appropriate operating temperature for the mechanoreceptors is maintained.

scholarly journals Aerial low-frequency hearing in captive and free-ranging harbour seals (Phoca vitulina) measured using auditory brainstem responses

2016 ◽  
Vol 202 (12) ◽  
pp. 859-868 ◽  
Author(s):  
Klaus Lucke ◽  
Gordon D. Hastie ◽  
Kerstin Ternes ◽  
Bernie McConnell ◽  
Simon Moss ◽  
...  
Keyword(s):  
Low Frequency ◽  
Auditory Brainstem ◽  
Phoca Vitulina ◽  
Auditory Brainstem Responses ◽  
Harbour Seals ◽  
Free Ranging

Seasonal and between-year variations in the diet of harbour seals in the Moray Firth, Scotland

1996 ◽  
Vol 74 (6) ◽  
pp. 1110-1121 ◽  
Author(s):  
D. J. Tollit ◽  
P. M. Thompson
Keyword(s):  
Diet Composition ◽  
Gadus Morhua ◽  
Prey Species ◽  
Temporal Variations ◽  
Short Term ◽  
Harbour Seals ◽  
Faecal Samples ◽  
Poor Indicator ◽  
Moray Firth ◽  
Merlangius Merlangus

Predictions concerning the effect of seals upon prey stocks require an understanding of temporal variations in diet composition. This study examined the extent of between-year and seasonal variations in the diet of harbour seals (Phoca vitulina) from the Moray Firth, Scotland, between 1989 and 1992. Analyses of fish otoliths and cephalopod beaks collected from 1129 faecal samples were used to derive estimates of the contribution made by each of 35 prey species, based on the number and mass consumed. The key prey, by mass, were sand eels (Ammodytidae) (47%), lesser octopus (Eledone cirrhosa) (27%), whiting (Merlangius merlangus) (6%), flounder (Platichthys flesus) (5%), and cod (Gadus morhua) (4%). Between-year and seasonal fluctuations in the contributions of these species were observed. Sand eels contributed 86–20% in summer and 91–49% in winter. Lesser octopus contributed 0–62% in summer and < 5% in winter, whilst whiting and cod contributed 2–34% in winter and 1–4% in summer. In contrast to 1988, clupeids were unimportant in winter. Differences in diet composition appeared to reflect local changes in the availability of food, especially overwintering clupeids. Results indicate that dietary information obtained from short-term studies can be a poor indicator of subsequent diet composition and should be treated with caution when used to predict the effect of seals on prey populations.

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