The physical and biochemical condition of Modiolus modiolus (L.) in selected Shetland voes

1981 ◽  
Vol 80 ◽  
pp. 299-321
Author(s):  
C. A. Comely
Keyword(s):  
Growth Rate ◽  
Density Distribution ◽  
Seasonal Variations ◽  
General Survey ◽  
Modiolus Modiolus ◽  
Environmental Variations ◽  
Biochemical Condition ◽  
Scottish Lochs

Synopsis1. A general survey of the sub-tidal populations of Modiolus modiolus (L.) to a depth of 18 or 21 m was carried out in five Shetland voes, with particular emphasis in Sullom Voe. Estimations of density distribution and growth rate were made.2. Commencing in June 1976 samples were collected at three-monthly intervals from two sites in Sullom Voe, and from one site in Cat Firth in 1977, to investigate seasonal variations in flesh and biochemical content. The data indicate that Shetland Modiolus are generally similar in their biology to those from Scottish lochs, and are liable to considerable variation between and within populations, with groups responding to environmental variations of very local extent.3. A list of animals found associated with Modiolus and their byssus complexes is given. As no effort was made to collect the fauna systematically or quantitatively, the list is not comprehensive.

Twilight observations of upper atmospheric sodium, potassium, and lithium

1969 ◽  
Vol 47 (1) ◽  
pp. 85-98 ◽  
Author(s):  
W. A. Gault ◽  
H. N. Rundle
Keyword(s):  
Density Distribution ◽  
Seasonal Variations ◽  
Resonance Line ◽  
Lower Layer ◽  
Atmospheric Transmission ◽  
Sodium Potassium ◽  
Sodium Layer ◽  
Lower Height ◽  
One Year

Twilight resonance emissions due to atmospheric sodium, lithium, and potassium have been measured for over one year. The existence of the potassium resonance line was verified by using an absorption cell.Several problems of measuring the emissions and of subsequently calculating a density distribution are discussed. The widths of about 13 km and the topside scale heights of about 4.5 km obtained for the sodium layer are significantly less than obtained at Saskatoon in previous measurements. Atmospheric transmission functions have been recalculated with the results that the sodium and lithium layers are both at about the same height of around 90 km. A lower height of about 85 km was obtained for the potassium layer.The seasonal variations of sodium and lithium twilight abundances are shown to be similar with additional sharp enhancements of lithium abundances thought to be due to natural and man-made injections of lithium. Any seasonal variations of the potassium abundances in the lower layer were masked by large day-to-day fluctuations.

Silage and hay intakes of housed red deer calves

1990 ◽  
Vol 1990 ◽  
pp. 77-77
Author(s):  
D J Kennedy
Keyword(s):  
Growth Rate ◽  
Seasonal Variations ◽  
Red Deer ◽  
Slow Growth ◽  
Red Meat ◽  
Limiting Factor ◽  
Low Fat ◽  
Slow Growth Rate ◽  
Quality Diet ◽  
Ad Libitum

There is an increasing interest in deer farming as an alternative livestock enterprise. One of the main reasons for this is that, currently, demand for venison (a low fat, red meat) is much greater than supply. However a major limiting factor to venison production is the slow growth rate of deer during the winter months. This is a consequence of their low feed intakes over this period. The aim of this study was to monitor feed intakes of housed, commercially-farmed red deer calves on a ‘good quality’ diet over the winter months to observe seasonal variations in appetite.One hundred and fifty four red deer calves (mainly June born) were observed in this study. There were four pens of stags containing 25, 23, 22 and 13 animals per pen, and three pens of hinds with 25, 25 and 21 animals per pen. All animals were offered forage ad-libitum plus 1.36 kg/d of a home-mix ration (12.9 MJ ME/kg DM, I62g CP/kg DM). One group of hinds was offered hay as the forage whilst the others all received silage.

A NONAUTONOMOUS MODEL FOR THE INTERACTIVE EFFECTS OF FEAR, REFUGE AND ADDITIONAL FOOD IN A PREY–PREDATOR SYSTEM

2021 ◽  
pp. 1-39
Author(s):  
NAZMUL SK ◽  
PANKAJ KUMAR TIWARI ◽  
YUN KANG ◽  
SAMARES PAL
Keyword(s):  
Growth Rate ◽  
Hopf Bifurcation ◽  
Seasonal Variations ◽  
Positive Periodic Solution ◽  
Oscillatory System ◽  
Interactive Effects ◽  
Predator Population ◽  
Prey Refuge ◽  
Additional Food ◽  
Predator System

The importance of fear, refuge and additional food is being increasingly recognized in recent studies, but their combined effects need to be explored. In this paper, we investigate the joint effects of these three ecologically important factors in a prey–predator system with Crowly–Martin type functional response. We find that the fear of predator significantly affects the densities of prey and predator populations whereas the presence of prey refuge and additional food for predator are recognized to have potential impacts to sustain prey and predator in the habitat, respectively. The fear of predator induces limit cycle oscillations while an oscillatory system becomes stable on increasing the refuge. The system first undergoes a supercritical Hopf-bifurcation and then a subcritical Hopf-bifurcation on increasing either the growth rate of prey or growth rate of predator due to additional food. Increasing the quality/quantity of additional food after a certain value causes extinction of prey species and rapid incline in the predator population. An extension is made in the model by considering the seasonal variations in the cost of fear of predator, prey refuge and growth rate of predator due to additional food. The nonautonomous model is shown to exhibit globally attractive positive periodic solution. Moreover, complex dynamics such as higher periodic solutions and bursting patterns are observed due to seasonal variations in the rate parameters.

Seasonal variations of equatorial spread-<i>F</i>

1994 ◽  
Vol 12 (1) ◽  
pp. 33-39 ◽  
Author(s):  
K. S. V. Subbarao ◽  
B. V. Krishna Murthy
Keyword(s):  
Growth Rate ◽  
Seasonal Variation ◽  
Seasonal Variations ◽  
Instability Mechanism ◽  
Sunspot Maximum ◽  
Vertical Drift ◽  
Different Seasons ◽  
Spread F ◽  
Seasonal Basis

Abstract. The occurrence of spread-F at Trivandrum (8.5°N, 77°E, dip 0.5°N) has been investigated on a seasonal basis in sunspot maximum and minimum years in terms of the growth rate of irregularities by the generalized collisional Rayleigh-Taylor (GRT) instability mechanism which includes the gravitational and cross-field instability terms. The occurrence statistics of spread-F at Trivandrum have been obtained using quarter hourly ionograms. The nocturnal variations of the growth rate of irregularities by the GRT mechanism have been estimated for different seasons in sunspot maximum and minimum years at Trivandrum using h'F values and vertical drift velocities obtained from ionograms. It is found that the seasonal variation of spread-F occurrence at Trivandrum can, in general, be accounted for on the basis of the GRT mechanism.

Some notes on the biology of the snake blenny, Lumpenus lampretaeformis on the west coast of Scotland

1979 ◽  
Vol 59 (2) ◽  
pp. 413-419 ◽  
Author(s):  
J. D. M. Gordon ◽  
J. A. R. Duncan
Keyword(s):  
Growth Rate ◽  
Seasonal Variation ◽  
West Coast ◽  
Seasonal Variations ◽  
Rapid Growth ◽  
The West ◽  
Harpacticoid Copepods ◽  
Rapid Growth Rate ◽  
Inshore Waters ◽  
Made In

Large catches of the snake blenny, Lumpenus lampretaeformis, have been made in the inshore waters of the west coast of Scotland. Analysis of these catches confirm the view that this species shows marked seasonal variations in abundance. The species lives for up to 9 years and has a rapid growth rate in the first 2 years. It feeds mainly on meiobenthic organisms, of which polychaetes, harpacticoid copepods, ostracods and nematodes are the most important. The reason for the seasonal variation in catch rate is discussed and it is speculated that it may result from the fossorial habit of the adults and the parental care of the eggs.

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