scholarly journals Age and Growth in Phocoena Phocoena Linnaeus, 1758 (Cetacea, Odontoceti) from the North Sea

1978 ◽  
Vol 48 (1) ◽  
pp. 16-28 ◽  
Author(s):  
W.L. van Utrecht
Keyword(s):  
North Sea ◽  
Posterior Part ◽  
The Body ◽  
Age And Growth ◽  
Body Measurements ◽  
Lower Growth ◽  
The North ◽  
The North Sea ◽  
Lower Growth Rate ◽  
The Mean

Data and material are collected from 106 Harbour Porpoises (P. phocoena) from the southern part of the North Sea. All animals are accidentally caught or found stranded. The greatest length for males in the sample is 151 cm, for females 186 cm. For detailed analysis of body measurements, 30 males and 37 females are selected, while from 20 males and 34 females teeth are used for age analysis. The analysis of the body measurements shows sexual dimorphism in the anterior and posterior part of the back, in the flukes and flippers and in the position of the genital slit. The maximum number of dentinal layers found in the teeth is 12. Males attain sexual maturity after the deposition of 5 dentinal layers, females when 6 layers are formed, at a body length of about 135 cm and 150 cm, respectively. Some evidence is found that the population of P. phocoena from the North Sea has a lower growth rate than the population from Canadian waters. The gestation period is estimated to be eleven months, the peak of the birth period being in June. The animals are born at a length varying between 67 cm to 80 cm. Growth of the visceral organs is isogonic. The mean weight of the organs is greater in females than in males.

Age and Growth of North Sea Echinoids

1985 ◽  
Vol 65 (3) ◽  
pp. 583-588 ◽  
Author(s):  
A. A. T. Sime ◽  
G. J. Cranmer
Keyword(s):  
Shallow Water ◽  
North Sea ◽  
Age And Growth ◽  
Eastern Area ◽  
The North ◽  
Small Variety ◽  
North Eastern ◽  
The North Sea ◽  
Northern North Sea

The genus Echinus is common throughout the entire northern North Sea. Echinus esculentus L. predominates in the shallow water off the eastern Scottish coast down to 100 m, while the small variety of Echinus acutus var. norvegicus (Düben and Koren) is rarely found in depths of less than 100 m and is most commonly located in the north-eastern area of the North Sea (Cranmer, 1985).

Long-term variability in North Sea zooplankton off the Northumberland coast: productivity of small copepods and analysis of trophic interactions

1988 ◽  
Vol 68 (1) ◽  
pp. 143-164 ◽  
Author(s):  
John C. Roff ◽  
Ken Middlebrook ◽  
Frank Evans
Keyword(s):  
North Sea ◽  
Trophic Interactions ◽  
Growth Rates ◽  
Larval Fish ◽  
The North ◽  
The North Sea ◽  
The Mean ◽  
June July

All groups of meso- and macro-zooplankton in the North Sea off Northumberland, at a depth of 53 m, were studied during a 15-year period (1969–83); copepod productivity was estimated from biomass and growth rates. Phytoplankton were seasonally bi-modal with peaks in April and August–October; copepods were uni-modal peaking in June–July. The predatory zooplankters: larval fish, decapods, ctenophores, medusae (the summer-autumn predators) peaked between May and September, while chaetognaths and euphausiids (the winter predators) peaked in December–January. Copepods and the summer-autumn predators were seasonally and inter-annually positively correlated, and declined in abundance from 1974 to 1980. Euphausiids and chaetognaths on the contrary increased in abundance during these years, and were seasonally and inter-annually negatively correlated to the copepods. The mean annual abundance of copepods was positively related to the previous winter's minimum, and inversely related to the abundance of chaetognaths and euphausiids. Annual copepod productivity averaged 1260 kJ m-2 year-1, and showed no relationship to other groups of plankton.

Reliability analysis of foundation stability for gravity platforms in the North Sea

1989 ◽  
Vol 26 (3) ◽  
pp. 359-368 ◽  
Author(s):  
Tien H. Wu ◽  
Oddvar Kjekstad ◽  
In-Mo Lee ◽  
Suzanne Lacasse
Keyword(s):  
North Sea ◽  
Reliability Index ◽  
Site Investigation ◽  
Offshore Structures ◽  
Material Strength ◽  
Strength Measurement ◽  
The North ◽  
The North Sea ◽  
Coefficients Of Variations ◽  
The Mean

The uncertainties encountered in the evaluation of foundation stability for four offshore gravity structures in the North Sea are reviewed. The uncertainties include those about the load, the material type, the material strength, and the analytical method. The means and coefficients of variations of these are used as inputs to compute the mean and coefficient of variation of the safety factor and the reliability index. The latter are used to assess the effect of various options in site exploration and strength measurement on foundation reliability. Key words: foundation, gravity platforms, offshore structures, probability, reliability, shear strength, site investigation, stability.

Monthly-mean residual flows through the Dover Strait, 1949–1972

1978 ◽  
Vol 58 (4) ◽  
pp. 965-973 ◽  
Author(s):  
D. Prandle
Keyword(s):  
Time Series ◽  
North Sea ◽  
Marine Biology ◽  
Small Variation ◽  
Mean Value ◽  
Residual Flow ◽  
Mean Flow ◽  
The North ◽  
The North Sea ◽  
The Mean

An estimate is made of the mean value of residual flow through the Dover Strait for each month over the 24–year period from 1949 to 1972. The estimates are based on results from a modelling investigation by Prandle (1978) where it was shown that the residual flow consists of three components, (a) a tidal residual, (b), a wind-driven residual and (c) a flow due to a long-term gradient in mean sea level. The components (a) and (c) are assumed to be constant and the value of (b) is deduced using wind data recorded by Dutch Light Vessels located in the southern North Sea.The mean flow over the whole period amounts to 155 × 103 m3 s–1 into the North Sea with a maximum value of 364 x 103 m3 s–1 and a minimum of – 15 × 103 m3 s–1 (out of the North Sea). One notable feature of the complete time series is the surprisingly small variation in the annual mean flows; perhaps this stability in the annual flow is of significance to the marine biology of the area.The validity of the computed time series is established by reference to comparable data including a 9–year record, from cross-channel submarine cables, of the potential induced by the flow of water through the Earth's magnetic field. Additional comparisons are also made with the results of a previous study of daily-mean flows.

Field measurements of wave-induced pressure over wind-sea and swell

1991 ◽  
Vol 230 ◽  
pp. 391-428 ◽  
Author(s):  
Dieter Hasselmann ◽  
Jens Bösenberg
Keyword(s):  
North Sea ◽  
Field Experiments ◽  
Field Measurements ◽  
The North ◽  
Wave Decay ◽  
The North Sea ◽  
Mean Water Level ◽  
The Mean ◽  
Wind Sea ◽  
Wave Induced

Results of two field experiments in the North Sea are presented. Pressure was measured at two fixed heights above the mean water level and correlated with simultaneous wave height measurements. Roughly 90 hours of data have been analysed and the results are in agreement with earlier results obtained by Snyder et al. (1981). Measurements over swell give no indication of wave decay or growth for waves travelling faster than the wind or against the wind.

scholarly journals On the conditions under which the "probable errors" of frequency distributions have a real significance

1915 ◽  
Vol 92 (634) ◽  
pp. 23-41 ◽  
Keyword(s):  
Standard Deviation ◽  
Frequency Distribution ◽  
North Sea ◽  
Probable Error ◽  
The Other ◽  
Adequate Description ◽  
Frequency Distributions ◽  
The North ◽  
The North Sea ◽  
The Mean

When we seek the value of a statistical constant, we may either consider the whole aggregate of individuals possessing characteristics of which the constant in question is a function, or we may limit ourselves, from choice or necessity, to the consideration of a ramdom sample of the whole population. The mean height of Englishmen of military age, at a given instant, is a constant which could be determined from a random sample. On the other hand, the mean weight of adult herrings frequenting the North Sea is necessarily to be determined only by a consideration of a sample of the whole population. Statistical constants calculated from a sample give us little information unless we know, at the same time, the manner in which the values may be expected to vary from ramdom sample to ramdom sample, i. e . the frequency distribution of the constant in many samples. The universal custom is to state the "probable error" of the constant, which is equivalent to giving the parameter of the values of the constant in the population as a whole. The parameter-the standard deviation of the frequency distribution-therefore ceases to provide an adequate description of the facts if the frequency distribution differs sensibly from the normal.

III.—Supernumerary Pectoral Fins in Raia circularis Loudon

1934 ◽  
Vol 53 ◽  
pp. 26-30
Author(s):  
W. F. Harper
Keyword(s):  
North Sea ◽  
The Body ◽  
Pectoral Girdle ◽  
Rare Occurrence ◽  
Pectoral Fins ◽  
Ventral Aspect ◽  
The North ◽  
Dorsal Aspect ◽  
Branchial Arches ◽  
The North Sea

A Male Sandy Ray (Raia circularis Loudon) caught in the North Sea, off Aberdeen, measured 47·5 cm. broad by 43 cm. long (excluding the tail) and exhibited an abnormality which is of very rare occurrence. This consisted of two well-developed fins situated ventrally and associated with the pectoral girdle and the last two branchial arches. The measurements of the fins in the formalin-hardened specimen were as follows: length, 8 cm.; breadth at base, 1·3 cm.; breadth at free end, 2 cm. (left), 3·2 cm. (right); thickness at base, 0·7 cm. The integument covering the lateral and medial borders of the proximal portion of each fin was continuous with that over the fourth and fifth gill clefts respectively. In addition, a strong fold of integument bound the proximal fourth of each fin to the ventral aspect of the body of the fish (fig. 1). A brownishred pigment was present on the ventral aspect of the terminal third of each, and a less marked pigmentation of the same colour on the dorsal aspect of the middle third. Small denticles, similar to those found elsewhere on the fins, were numerous on the distal third, but were more abundant on the dorsal aspect.

The north sea storm surge of 31 January and 1 February 1953

1954 ◽  
Vol 246 (915) ◽  
pp. 371-400 ◽  
Keyword(s):  
Storm Surge ◽  
North Sea ◽  
Frictional Coefficient ◽  
Future Research ◽  
English Channel ◽  
Tractive Force ◽  
The North ◽  
The North Sea ◽  
The Mean ◽  
Sea Storm

Using observed hourly heights of tide at thirty-one stations in the North Sea and two in the English Channel, the storm surge of 31 January and 1 February 1953 has been investigated in the light of the meteorological conditions prevailing. The major cause of the disturbance is shown to be the strong northerly winds in and to the north of the North Sea, modified at each station by local wind and barometric effects. An increase of 2 ft. in the mean level of the North Sea during the disturbance has been deduced, and the response of the sea as a whole to the disturbing winds has been examined. Geostrophic effects have been remarked in both the growth and decay of the disturbance. Estimates have been made of the air/sea frictional coefficient on two separate occasions during the period considered, assuming the tractive force of the wind to vary as the square of its velocity. These estimates are in agreement with accepted values. The partial transmission of this large surge through the Straits of Dover has been shown as an im portant factor, influencing the levels immediately to the north of the Straits. Prediction of the surge at Southend by a previously established formula has given only fair results, but the errors have been explained in terms of the facts previously presented and the approximations upon which the formula is based. Suggestions for future research into the improvement of surge prediction formulae have been made.

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