scholarly journals Biological processes in the North Sea: comparison of Calanus helgolandicus and Calanus finmarchicus vertical distribution and production

2010 ◽  
Vol 33 (1) ◽  
pp. 85-103 ◽  
Author(s):  
S. H. Jonasdottir ◽  
M. Koski
Keyword(s):  
Vertical Distribution ◽  
North Sea ◽  
Calanus Finmarchicus ◽  
Biological Processes ◽  
The North ◽  
The North Sea ◽  
Calanus Helgolandicus

Studies on a Calanus Patch III. The quantity of food eaten by Calanus finmarchicus

1963 ◽  
Vol 43 (2) ◽  
pp. 349-371 ◽  
Author(s):  
D. H. Cushing ◽  
T. Vucetic
Keyword(s):  
Water Temperature ◽  
North Sea ◽  
Calanus Finmarchicus ◽  
Algal Production ◽  
The North ◽  
The North Sea ◽  
Grazing Mortality ◽  
And Diffusion ◽  
Grazing Capacity ◽  
Food Consumed

The purpose of this paper is to assess the grazing capacity of Calanus finmar-chicus (Gunner.) in terms of the quantity of food eaten in the sea. The part played in the growth of the animal by the quantity eaten will only be briefly discussed. The parts played by nutrient lack, sinking and diffusion on the algal productive rates will also be discussed, leading to the conclusion that grazing mortality is the most effective controlling agent on algal production.A subsidiary purpose of this paper is to relate changes in the weight of Calanus finmarchicus to changes in food consumed and to changes in water temperature. Measurements of C. finmarchicus have been made by a number of workers (Adler & Jespersen, 1920; Russell, 1928; Marshall, 1933; Stormer, 1929; Bogorov, 1934; Jespersen, 1939; Clarke & Zinn, 1937). It will be shown that in the North Sea, in spring, the greatest changes in weight are most readily related to changes in quantities of food consumed.

scholarly journals Vertical distribution of pre-settled sandeel (Ammodytes marinus) in the North Sea in relation to size and environmental variables

2003 ◽  
Vol 60 (6) ◽  
pp. 1342-1351 ◽  
Author(s):  
Henrik Jensen ◽  
Peter J Wright ◽  
Peter Munk
Keyword(s):  
Vertical Distribution ◽  
Water Column ◽  
North Sea ◽  
Distribution Patterns ◽  
Food Concentration ◽  
The North ◽  
Vertical Distributions ◽  
The North Sea ◽  
Drift Trajectory ◽  
Vertical Positioning

Abstract Vertical distribution patterns of larval and juvenile sandeels were investigated at four locations in the North Sea. Sandeels between 6 and 65 mm were found to depths of 80 m, with vertical distributions dependent on both length and environmental factors. At one location with a stratified water column, the highest densities were found during the day in midwater where food concentration was also highest. In areas without marked vertical hydrographic gradients, larvae were relatively more abundant in surface waters during the day. At all locations, larvae of all sizes were generally more homogeneously distributed in the water column during night than during day. The extent of vertical migration, as measured by the standard deviation of the mean depth, increased generally with length. Gear avoidance was evident for larvae ≥20 mm. Catch efficiency generally depended on both length class and surface light intensity. A simulated drift pattern of larvae, based on ADCP current measurements from two locations, predicts that the horizontal drift trajectory would only be affected slightly by the vertical positioning of the larvae in the water column during the time of sampling. The implication of vertical migrations for dispersal of larvae away from the spawning grounds is discussed.

Composition and origin of milky water in the North Sea

1980 ◽  
Vol 60 (3) ◽  
pp. 759-768 ◽  
Author(s):  
J. K. Volkman ◽  
R. R. Gatten ◽  
J. R. Sargent
Keyword(s):  
North Sea ◽  
Mass Spectra ◽  
Oxidative Degradation ◽  
Wax Esters ◽  
Calanus Finmarchicus ◽  
Wax Ester ◽  
Capillary Gc ◽  
The North ◽  
The North Sea ◽  
Calanus Species

An occurrence of ‘milky water’ which covered a wide area of the North Sea in June 1975 is described. The water contained 20 mg/1 of an oil which was shown by capillary GC-MS to consist mainly (> 80%) of two wax esters 34:1 and 36:1. Analysis of the acids and alcohols released by hydrolysis, and interpretation of the wax ester mass spectra, indicated that the 34:1 ester was almost entirely composed of the alcohol-acid combination 20:1–14:0 and the 36:1 ester was composed of 22:1–14:0 (75%) and 20:1–16:0 (19%). Wax esters of virtually the same composition predominate in the lipids of the copepod Calanus finmarchicus which has the implication that the ‘milky water’ was caused by ageing of the oil released following a mass mortality of copepods. The lack of polyunsaturated wax esters and of astaxanthin is ascribed to oxidative degradation of these labile lipids following release into the sea. A copepod origin for the milky water is further supported by its containing small amounts of cholesterol and pristane, both of which are common to Calanus species.

scholarly journals Does copepod size determine food consumption of particulate feeding fish?

2013 ◽  
Vol 71 (1) ◽  
pp. 35-43 ◽  
Author(s):  
Mikael van Deurs ◽  
Marja Koski ◽  
Anna Rindorf
Keyword(s):  
Food Consumption ◽  
North Sea ◽  
Fish Larvae ◽  
Handling Time ◽  
Growth Conditions ◽  
Calanus Finmarchicus ◽  
Fish Feeding ◽  
The North ◽  
The North Sea ◽  
Particulate Feeding

Abstract van Deurs, M., Koski, M., and Rindorf, A. Does copepod size determine food consumption of particulate feeding fish? – ICES Journal of Marine Science, 71: . The climate-induced reduction in the mean copepod size, mainly driven by a decrease in the abundance of the large Calanus finmarchicus around 1987, has been linked to the low survival of fish larvae in the North Sea. However, to what extent this sort of reduction in copepod size has any influence on adult particulate feeding fish is unknown. In the present study, we investigated the hypothesis that the availability of the large copepods determines food consumption and growth conditions of lesser sandeel (Ammodytes marinus) in the North Sea. Analysis of stomach content suggested that food consumption is higher for fish feeding on large copepods, and additional calculations revealed how handling time limitation may provide part of the explanation for this relationship. Comparing stomach data and zooplankton samples indicated that lesser sandeel actively target large copepods when these are available. Finally, we observed that the length of lesser sandeel began to decrease in the late 1980s, simultaneously with the C. finmarchicus decline.

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