ICES Journal of Marine Science: Journal du Conseil

Smed, Jens

doi: 10.1093/icesjms/32.2.155pmid: N/A

The hydrographic department of the ICES Central Office, its origin and activities are described. These follow mainly from its function as a hydrographic data centre for the ICES region, implying screening, filing, distribution, and publishing of the data, and preparation on their basis, of charts, graphs and tables of mean values and anomalies. Some contributions of the Service to the unification of hydrographic work are mentioned. Information is given about the staff throughout the years, from the start and during more than a generation headed or supervised by Mar: in KNUDSEN. The present plans for a rearrangement of the Service are touched upon. There is an appendix listing the papers published by the staff members.

Goldman, Charles R.

doi: 10.1093/icesjms/32.2.172pmid: N/A

The use of barium carbonate for calibrating the Geiger Müller counting equipment routinely used in primary productivity studies in marine and fresh waters has resulted in serious errors. Because the radioactivity of algae rather than barium carbonate is being measured, algae are the best radioactive source for determining the efficiency of GM counting. The absolute activity of any particular thickness of filtered algae as well as that of a C14 label can be accurately determined in gas phase. This direct procedure eliminates tacit assumptions of self-absorption and backscattering effects in calibration. The GM counting efficiencies of algae varied with species to species and with sample weight. The marine diatom Skeletonema was found to have a particularly low counting efficiency.

Szekielda, Karl-Heinz

doi: 10.1093/icesjms/32.2.180pmid: N/A

The nutrients present in seawater are assumed to be related to the decomposition of organic material. A simple description of the production and decomposition of organic material, in terms of chemical reactions based on stochiometrical relationships, leads to a model used to predict the values of oxygen, nitrate, and phosphate found in seawater. Data from the Indian Ocean are in good agreement with those predicted and deviations in respect of nitrate can be accounted for by denitrification.

Stefánsson, U.

doi: 10.1093/icesjms/32.2.188pmid: N/A

Nitrate-phosphate relationships in the northern Irminger Sea in August-September 1965 indicate almost identical ratio of change in Atlantic water and Polar water, δN:δP = 14.3:1. In Atlantic water the nutrients are utilized or regenerated in approximately the same ratio as it is in the water, whereas in Polar water the concentration ratio is smaller than the ratio of change, leading to nitrate depletion when the phosphate concentration is still 0.2–0.3 μg-at./l. Since the concentration ratio varies significantly with salinity, the nitrate concentration can be expressed empirically as a function of both phosphate and salinity. Data collected in the southern and the northern Irminger Sea in February-March 1967 indicate that the same nitrate-phosphate relationships also hold in the winter-time.In the shelf area inside and outside Faxaflói, West Iceland, regional variations are small in nutrient concentrations during the winter months, but nitrate-phosphate concentration ratios are lower than in the more oceanic area. Outside the 100 metre depth contour the simultaneous changes in phosphate and nitrate concentrations follow a linear relationship as in the Irminger Sea proper, but at near-shore stations anomalously low N/P ratios are found during spring, summer and autumn. Possible causes of these apparent discrepancies are discussed.

Banoub, M. W.; Burton, J. D.

doi: 10.1093/icesjms/32.2.201pmid: N/A

The concentration of dissolved silicate in Southampton Water in December 1966 ranged from 320 to 3320 μg Si/l, and showed a highly significant inverse correlation with salinity; the values fitted satisfactorily to a linear relationship. The distribution of dissolved silicate, in the absence of any significant biological activity, was governed principally by the mixing processes in the estuary; there was no evidence of removal of dissolved silicate by inorganic processes. The concentration of particulate silicon was on average more than twice that of dissolved silicon.

Grandperrin, R.; Caboche, C.

doi: 10.1093/icesjms/32.2.209pmid: N/A

Sixty-eight micronekton and macroplankton samples collected with a 3 m Isaacs-Kidd Midwater Trawl were preserved with ten percent buffered formaldehyde solution. An investigation of wet weight loss was carried out over a period of 7 months. The loss varies according to the material and reached 45% of the live weight with gelatinous organisms. A few samples were frozen in seawater at a temperature of −20°C. The weight loss subsequent to thawing reached higher percentages than with preservation in formaldehyde. Dry weight determinations have been made for a few samples. Wet weight loss subsequent to preservation and freezing seems to be directly related to the water content of organisms. It is recommended not to estimate biomass before several months of preservation.

Roger, C.; Wauthy, B.

doi: 10.1093/icesjms/32.2.216pmid: N/A

To overcome the drawbacks of individual measurements of the large number of Euphausiids caught by the 3·3 m Isaacs-Kidd MWT used aboard “Coriolis”, from the Centre ORSTOM de Noumea (New-Caledonia) in the western Pacific, a method has been devised t sort the preserved organisms into some arbitrary groups of size. The device consists of a set of grilles made from equidistant glass rods, through which the organisms are sieved by the reciprocating motion of the grilles in the water. Tests on Thysanopoda tricuspidata have shown that sorting by number as well as by weight is effective and that the reproducibility is good. On practical grounds the sorting by size on the whole euphausiid catch goes before its separation by species.

Rakusa-Suszczewski, S.

doi: 10.1093/icesjms/32.2.226pmid: N/A

Analysis of Hensen net samples collected in the Celtic Sea and English Channel in 1965 suggests that Tomopteris helgolandica is a predator on Parasagitta elegans, sucking liquid food from the body of its prey. Support for the hypothesis is provided by the capture of dead P. elegans with perforations of the body wall. The results are discussed in relation to the size distribution of Tomopteris in the samples, to the time of day at which the net hauls were made, and to the vertical distribution of P. elegans and Sagitta setosa.

Smith, Paul E.; Counts, Robert C.; Clutter, Robert I.

doi: 10.1093/icesjms/32.2.232pmid: N/A

The problem of clogging is inherent in sampling plankton and this paper reports a study of clogging rates in tests of design variables of plankton nets, such as mesh size, filtering area, and net form. Telemetering flow meters were used to determine the effects of these variables on the rate of clogging of pairs of plankton nets under tow in waters of different clarity. Metering of flow is necessary for evaluating clogging. A water clarity measurement is not useful for predicting clogging rate and the gross appearance of the net after the tow is not necessarily a reliable indicator of whether clogging has lowered filtration efficiency during the tow. Fine mesh nets with comparable mesh aperture area filter as well initially as do nets with larger apertures but clog much more rapidly. Compared to silk with mesh apertures 0.550 mm wide, nylon with apertures 0.333 mm, 0.201 mm and 0.101 mm wide clog 3, 5 and 35 times as rapidly. In the cylinder-cone nets of 0.333 mm nylon mesh, the volume filtered at more than 85% efficiency was increased six-fold by doubling the filtering area. An equation describing the relation of the ratio of filtering area to mouth area for 0.333 mm nylon is:log10R=0.38log10VA-0.17where R is the ratio of filtering area to mouth area, V is the volume to be filtered and A is the mouth area of the net. The cylinder and cylinder-cone nets were superior in sustained filtration efficiency to cone-shaped nets. We attribute this advantage to the oscillations of the cylindrically placed mesh which tend to clean the mesh at a higher rate. An example is given of the method by which a new net was designed to lessen the probability of clogging.

Kutty, M. Krishnan; Qasim, S. Z.

doi: 10.1093/icesjms/32.2.249pmid: N/A

Some methods for estimating the optimum age of exploitation (ty)and the potential yield (Y) in fish populations have been described under allometric and isometricconditions of growth. The relative constancy of ty and Y under allconditions of exploitation indicates that these parameters, in the absence of a long series of data, could be used for measuring the fishing efficiency.