scholarly journals Directional Bilateral Asymmetry in Fish Otolith: A Potential Tool to Evaluate Stock Boundaries?

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 987
Author(s):  
Kélig Mahé ◽  
Kirsteen MacKenzie ◽  
Djamila Ider ◽  
Andrea Massaro ◽  
Oussama Hamed ◽  
...  
Keyword(s):  
North Sea ◽  
Directional Asymmetry ◽  
Stock Identification ◽  
English Channel ◽  
Bilateral Asymmetry ◽  
Otolith Shape ◽  
Southern North Sea ◽  
Solea Solea ◽  
Algerian Coast ◽  
The Right

The otolith, found in both inner ears of bony fish, has mainly been used to estimate fish age. Another application that has been developing significantly in recent years, however, is the use of otolith shape as a tool for stock identification. Often, studies have directly used the shape asymmetry between the right and left otoliths. We tested the magnitude of directional asymmetry between the sagittal otoliths (left vs. right) of 2991 individuals according to their catch locations, and we selected species to evaluate whether directional asymmetry may itself be a tool to evaluate stock boundaries. Elliptical Fourier descriptors were used to describe the otolith shape. We used a flatfish, the common sole (Solea solea, n = 2431), from the eastern English Channel and the southern North Sea as well as a roundfish, the bogue (Boops boops, n = 560), from the Mediterranean Sea. Both species showed significant levels of directional asymmetry between the testing locations. The bogue otoliths showed significant asymmetry for only 5 out of 11 locations, with substantial separation between two large areas: the Algerian coast and the western part of the Italian coast. The sole otoliths showed significant asymmetry in the shape analysis (3.84%–6.57%), suggesting a substantial separation between two large areas: the English and French parts of the English Channel and the southern North Sea. Consequently, directional bilateral asymmetry in otolith shape is a potential new method for stock identification.

Traffic Lanes and the Collision Regulations

1979 ◽  
Vol 32 (1) ◽  
pp. 137-138
Author(s):  
J. G. Kemp-Luck
Keyword(s):  
North Sea ◽  
English Channel ◽  
Near Misses ◽  
Southern North Sea ◽  
The North ◽  
Traffic Lane ◽  
The North Sea ◽  
The Right ◽  
Crossing Vessels

As a watch-keeping officer on ships daily crossing the North Sea and English Channel 1 was interested to read Commander Paton's paper on ‘Navigation in the English Channel and the Southern North Sea’ in the January 1978 issue of this Journal. Since the introduction of the traffic separation schemes many of us have been concerned about the possibility of an accident whilst crossing the lanes. It is an almost nightly experience to have ‘near misses’ and occasionally more than one ‘near collision’ inside the hour, with people who appear to think that, because they are in a traffic lane and going the right way, everyone else must keep clear of them. No attempt is made to avoid crossing vessels in accordance with the Collision Regulations and, in spite of flashing the warning five shorts and blowing five shorts on the whistle, we often have ships call us to demand we keep out of their way, contrary to all regulations, and frequently forcing us to take drastic evasive action.

scholarly journals Size-effect, asymmetry, and small-scale spatial variation in otolith shape of juvenile sole in the Southern North Sea

Hydrobiologia ◽  
2018 ◽  
Vol 845 (1) ◽  
pp. 95-108 ◽  
Author(s):  
Sophie Delerue-Ricard ◽  
Hanna Stynen ◽  
Léo Barbut ◽  
Fabien Morat ◽  
Kelig Mahé ◽  
...  
Keyword(s):  
Size Effect ◽  
Spatial Variation ◽  
North Sea ◽  
Small Scale ◽  
Otolith Shape ◽  
Southern North Sea

scholarly journals Investigations Upon the Water Movements in the English Channel. Summer, 1924

1927 ◽  
Vol 14 (3) ◽  
pp. 685-721 ◽  
Author(s):  
J. N. Carruthers
Keyword(s):  
North Sea ◽  
English Channel ◽  
Average Speed ◽  
Southern North Sea ◽  
The North ◽  
Westerly Winds ◽  
The North Sea

In July, 1924, 250 floating, and an equal number of bottom-trailing, bottles were put out at selected places in the western English Channel. Fifty of each type were put out at each of the two routine Stations E2 and E3, and the same number was “liberated” at each of three selected stretches along the steamship route from Southampton to St. Malo. Those surface bottles, which did not strand locally, travelled rapidly up Channel towards the North Sea and across it. Many bottles arrived in the Skager-Rack after performing their journey of some 700 miles at the rate of 6 miles a day and more. An adequate study of wind conditions, as recorded at several stations along the length of the Channel and at one station in the southern North Sea, revealed the fact that there was, for some 5½ months (counting from the time of liberation of the bottles), an almost uninterrupted predominance of south-westerly winds—as recorded at all stations considered. The whole area of the Channel was swept by south-westerly winds of average speed of some 9 miles a day for at least 5½ months subsequent to the time of putting out of the bottles. July, 1924, had (according to the Falmouth Observatory records) the largest proportion of westerly winds experienced for 54 years; 20 days of this month had winds with westerly components. The association of the unusually persistent westerly winds with the rapid travel of surface bottles towards and across the North Sea is interesting.

Movements and distribution of cod (Gadus morhua) in the southern North Sea and English Channel: results from conventional and electronic tagging experiments

2007 ◽  
Vol 87 (2) ◽  
pp. 599-613 ◽  
Author(s):  
David Righton ◽  
Victoria Anne Quayle ◽  
Stuart Hetherington ◽  
Gary Burt
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
English Channel ◽  
Seasonal Movement ◽  
Southern North Sea ◽  
The North ◽  
Fisheries Policy ◽  
The Uk ◽  
Electronic Tags

The sub-structure of Atlantic cod (Gadus morhua) stocks in the North Sea has important consequences for fisheries management as the Common Fisheries Policy moves towards a more regional approach. We investigated the movements, distribution and behaviour of cod in the southern North Sea (ICES IVc) and English Channel (ICES VIId) by re-analysing historic data from conventional tagging experiments, and by conducting new experiments with electronic tags. Cod tagged and released in IVc showed a northwards shift in distribution during the feeding season consistent with a homing migration away from spawning grounds along the coasts of the UK and the Netherlands. In contrast, cod tagged and released in VIId did not exhibit a consistent pattern of seasonal movement. Many cod released in VIId were subsequently recaptured close to their release position, although some moved out of the Channel and into the southern North Sea. Overlap between the recapture areas of cod released in the different management areas was no more than 25% in either the spawning or feeding season. Behavioural data from electronic tags suggest that cod in IVc make use of tidal streams to migrate northwards and eastwards in spring, whereas selective tidal stream transport was rarely exhibited by cod tagged and released in VIId. Overall, the evidence suggests that there are behavioural differences between cod in IVc and VIId that limit the mixing of cod from these two areas during the feeding and spawning seasons.

scholarly journals Direction Indication Lights

1969 ◽  
Vol 22 (2) ◽  
pp. 253-253
Author(s):  
H. V. Anguish
Keyword(s):  
North Sea ◽  
English Channel ◽  
Southern North Sea ◽  
Centre Line ◽  
Light Flashes

A Recent Admiralty Notice to Mariners (No. 1555/1968) advises that a vessel trading the southern North Sea and the English Channel has been fitted with experimental direction indication lights in order to indicate to an approaching vessel the direction in which she is altering course and the duration of the alteration. The positioning of these lights are 10·5 ft. higher than the after masthead light and 4 ft. outboard on each side of the centre line, and they are coloured red to port and green to starboard. When altering course the appropriate light flashes until the vessel is steadied up on her new course.

Sole larval distribution (Solea solea) in the eastern English Channel and Southern Bight of the North Sea

2001 ◽  
Vol 81 (4) ◽  
pp. 673-678 ◽  
Author(s):  
A. Grioche ◽  
P. Koubbi ◽  
X. Harlay ◽  
B. Sautour
Keyword(s):  
North Sea ◽  
Environmental Parameters ◽  
English Channel ◽  
Southern Bight ◽  
Intermediate Variable ◽  
Larval Stages ◽  
The North ◽  
Larval Distribution ◽  
Solea Solea ◽  
The North Sea

The distribution of sole (Solea solea) eggs and larvae were described from two cruises conducted in April and May 1995 along the French coast of the eastern English Channel and the Belgian coast of the Southern Bight of the North Sea. Sole migration was investigated using larval stages and univariate spatial analysis as geostatistics (variograms). Important environmental parameters were selected by comparison with larval distribution. Path analysis was used to remove spatial correlation and to define links between abundance and environmental variables.  Sole larvae were found to be coastal throughout their development. Strong links between larval distribution and environmental parameters were identified, particularly for the younger stages which were found in higher abundance in areas of high chlorophyll-a concentration. The association was not direct, suggesting that the larval spatial distribution was influenced by an undetermined, intermediate variable, such as larval prey. Sole larvae are retained in the coastal area throughout ontogeny despite the strong hydrodynamics which characterize the region. Larval distribution resulted from behavioural mechanisms as well as environmental influences.

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