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doi: 10.1093/icesjms/33.2.126pmid: N/A
The major constituents in seawater have been recently determined in a series of samples from the main oceans and seas. According to a resolution of the International Union of Pure and Applied Chemistry (IUPAC), new atomic weights based on 12C = 12.0000 are in use since 1. Jan. 1962. On the basis of these two developments, an independent table for the ionic composition of seawater is calculated. The Wattenberg equation for the estimation of calcium in seawater is corrected according to the recent values of calcium/chlorinity ratio and specific alkalinity. The variation of calcium and alkalinity with depth is evaluated and their effect on the salinity values obtained either by chlorinity or conductivity is estimated.
Burton, J. D.; Liss, P. S.; Venugopalan, V. K.
doi: 10.1093/icesjms/33.2.134pmid: N/A
Measurements of salinity and concentration of dissolved silicon were made on samples collected in the Test arm of Southampton Water in a number of surveys during 1968. The values show highly significant inverse correlations and fit closely to linear relationships. The distribution of dissolved silicon was controlled essentially by mixing processes. Biological activity in the summer had a negligible effect. For each survey, the concentration of dissolved silicon in the diluting water, as calculated from regression analysis of values over the whole range of salinity, agreed closely with that measured in river water entering the estuary. These findings indicate that there was no appreciable removal of dissolved silicon by inorganic processes. The Hamble Estuary was investigated on one occasion. Mixing processes were again found to be the primary factor affecting the distribution of dissolved silicon but the results suggested that a small fraction (not more than 10%) of the dissolved silicon entering in river water was removed inorganically.
doi: 10.1093/icesjms/33.2.141pmid: N/A
A preliminary investigation was made in February 1968 of the relationship between the concentration of dissolved silicon and chlorosity in the Vellar Estuary. The Vellar River water and the sea water at the mouth of the estuary differed in concentration of dissolved silicon by about two orders of magnitude and the extent of dilution with fresh water was the dominant influence on the distribution of dissolved silicon in the estuary. Biological effects appear to have been unimportant except towards the mouth of the estuary where the concentration of dissolved silicon was lowest. In the upper estuary, where Vellar River water mixed with water of intermediate chlorosity from the lower estuary, there was some removal (on average not more than 10%) of the dissolved silicon entering in river water. The extent to which further mixing was accompanied by removal is uncertain. The distribution in the lower estuary could be interpreted as indicating either that there was further and more substantial removal, or that there was a considerable contribution of fresh water from irrigation canals which had a lower concentration of dissolved silicon than that in the Vellar River water, or that both these processes occurred. Some implications of these alternative interpretations are discussed.
doi: 10.1093/icesjms/33.2.149pmid: N/A
A short review of the literature on the distribution and ecology of Pleurobrachia is given and supplemented by data taken between 1925 and 1968 in the Scottish area. It is a neritic species in the northern North Sea and reaches its greatest abundance in October and November following a possible minor peak of abundance in early summer, but in some years (e.g. 1965) the summer peak can exceed that of the autumn.Pleurobrachia is a non-selective carnivore, feeding on what is available in the plankton, and swarms can greatly reduce the amount of zooplankton in large areas of water. Spawning is continuous while conditions are suitable, but changing conditions can sometimes give the effect of two separate spawnings in a year.Although there are reports in the literature of Pleurobrachia eating eggs and larvae to the extent of reducing the recruitment potential of the fish and shellfish, this has not been found in the Scottish area where crustaceans form 80% of the diet, and reaching 97%. Because of the reduction in zooplankton, however, swarms of Pleurobrachia could be responsible for larval fish mortalities, even if the fish themselves are only rarely eaten, and they could affect also adult herring and other plankton feeders.There is a rapid increase in the numbers of cercarian parasites of Pleurobrachia from August to September.
Jones, Margaret; Spencer, C. P.
doi: 10.1093/icesjms/33.2.169pmid: N/A
The phytoplankton of the Menai Straits has been sampled quantitatively at twice weekly intervals over a period of thirty months in the years 1961–63.Synoptic physical measurements (salinity, temperature and secchi disc readings) and chlorophyll determinations were also made. The variation in species composition of the standing crop of phytoplankton in these waters throughout the period and the dynamics of the main bloom of diatoms are analysed. The phytoplankton in these waters usually exhibit only one major multi-species bloom in April or May but individual species sometimes produce secondary blooms later in the year. The quantitative records and the chlorophyll results show that large standing crops of phytoplankton do not usually occur in these waters which are, none the less, markedly enriched in nutrients by land drainage. During the main spring bloom, various species of Rhizosolenia are usually dominant but the growth of Phaeocystis which usually succeeds the spring diatom bloom dominates the phytoplankton for extended periods in the early summer. At these times virtually all the phytoplankton in the water are small flagellates. Even during the bloom of the larger centric diatoms, the nanoplankton species form the greater proportion (by volume) of the phytoplankton standing crop in these waters
doi: 10.1093/icesjms/33.2.181pmid: N/A
Scales and otoliths from 1150 herring were examined to test the accuracy with which age can be determined. Comparison of results by the two methods showed disagreements increasing with age and an overall agreement of only 68.0%. Ages from scales were higher than those from otoliths. Mean lengths from otolith-aged herring were more variable than those from scale-aged fish and length distributions beyond age 5 were significantly different. In the Gulf of St. Lawrence, where larger and older herring predominate in the catches, scales are more reliable than otoliths for age analysis.
doi: 10.1093/icesjms/33.2.192pmid: N/A
Re-examination of the original data of the ICES displacement experiments carried out in the first decade of this century showed that plaice return towards the initial ground, even when displaced over considerable distances to unfamiliar territory.The speed of homing is low and the majority of the transplanted fish never returns exactly to the ground where they were caught. After one year the cluster of transplanted fish, as a whole, has reached a position between the catch and the release position. No further gain in homing was achieved in the second year after release, the cluster of displaced fish after two years more or less coinciding with the position reached after one year. Plaice displaced over a distance of 190 miles or more only showed a homing tendency in the first two months after release.A number of displacement experiments showed that recruits were not guided by the residual bottom currents when selecting their spawning grounds. Adult plaice, revisiting their spawning grounds, did not use the currents as directional clues for migration.
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