Since the advent of nuclear fission, considerable interest has been aroused in the biological fate of strontium, as two isotopes of this element are among the longer-lived fission products of uranium. Strontium 90, in particular, constitutes the major hazard in old fission products because it is readily taken up by all kinds of plants and may then be concentrated in the bones of animals feeding on the plants. Strontium 90 contamination may be derived from fall-out from atomic explosions or from uncontrolled disposal of fission products. The oceans should receive more than twice as much Strontium 90 from fall-out as the continents because 70% of the surface area of the globe is covered by sea. The oceans are also used, though to a very limited extent at present, for the disposal of fission products from reactor wastes. Hence it is obviously important to study the behaviour of strontium in marine organisms in order to evaluate the health hazard caused by controlled or uncontrolled radioactive contamination of sea water. Barium has only relatively short-lived fission-product isotopes, but can readily be studied at the same time as strontium because of its similar chemistry.

The upper reaches of the deep ocean contain many bathypelagic fishes with a capacious, gas-filled swimbladder. But living within and below this region are also numerous species in which this hydrostatic organ is absent or markedly regressed (Marshall, in preparation). In the neritic province nearly all the fishes that swim freely at the various water levels (and can stay poised at a particular level without undue effort) have a well-developed swimbladder, the capacity of which is about equal to 5 % of the body volume (Jones & Marshall, 1953). Having this amount of gas, these fishes are able to keep their weight in water close to the vanishing point. If such a fish were deprived of its swimbladder, it could keep at a constant level only by exerting a down-ward force equivalent to 5 % of its weight in air. The swimbladder thus saves the fish the energy needed for such effort, which is quite appreciable.

The Galatheidea are divided into two families, the Galatheidæ and the Porcellanidæ, which differ from each other in their feeding habits as well as their structure.

Galathea dispersa has been taken as typical of the Galatheidæ. An examination of the gut contents shows that the food in the stomach consists of finely divided particles mixed with sand and detritus. In addition larger pieces of animal and vegetable matter are occasionally found. Observations of the animals in captivity show that they feed by two methods; either large pieces of food are seized by the chelæ and maxillipeds and passed to the mandibles or, as is more usual, the third maxillipeds are used to collect finely divided material from the substratum.The setæ on the terminal segments of the maxillipeds form a dense tuft which sweeps over the substratum, loosening and collecting small particles. The terminal tufts are cleaned out by the setse of the second maxillipeds, and the food passed to the mouth.

The spread of the immigrant brown alga Sargassum muticum ( Yendo) Fensholt, within European waters is chronicled from 1973–1981. New populations of the attached alga are listed together with maps indicating the annual addition of sites. No populations of the alga were known beyond the bounds of the Solent region, southern Britain, until after 1975.

The age of the original Sargassum population found at Bembridge in 1973, and the discovery of drifting S. muticum in 1971, seems to date the initial introduction of the alga in the Channel as possibly the late 1960s.

This paper presents the establishment of Sargassum muticum as a permanent addition to the European marine flora. It is hoped that its future spread will continue to be documented, providing useful information upon the invasion strategy of an ‘aggressive’ introduced marine species.

Jellyfish medusae prey on zooplankton and may impact fish recruitment both directly (top-down control) and indirectly (through competition). Abundances of Aurelia aurita, Cyanea lamarckii and Cyanea capillata medusae (Scyphozoa) in the North Sea appear to be linked to large-scale inter-annual climatic change, as quantified by the North Atlantic Oscillation Index (NAOI), the Barents Sea-Ice Index (BSII) and changes in the latitude of the Gulf Stream North Wall (GSNW). Hydroclimatic forcing may thus be an important factor influencing the abundance of gelatinous zooplankton and may modulate the scale of any ecosystem impact of jellyfish. The population responses are probably also affected by local variability in the environment manifested in intra-annual changes in temperature, salinity, current strength/direction and prey abundance. Aurelia aurita and C. lamarckii in the north-west and south-east North Sea exhibited contrasting relationships to change in the NAOI and BSII: north of Scotland, where the North Sea borders the Atlantic, positive relationships were evident between the abundance of scyphomedusae (data from 1974 to 1986, except 1975) and the indices; whereas west of northern Denmark, a region much less affected by Atlantic inflow, negative relationships were found (data from 1973 to 1983, except 1974). Weaker negative relationships with the NAOI were also found in an intermediate region, east of Scotland, for the abundance of A. aurita and C. capillata medusae (1971 to 1982). East of Shetland, the abundance of jellyfish was not correlated directly with the NAOI but, in contrast to all other regions, the abundances of A. aurita and C. lamarckii (1971 to 1986, not 1984) were found to correlate negatively with changes in the GSNW, which itself was significantly positively correlated to the NAOI with a two year lag. On this evidence, we suggest that, for jellyfish, there exist three regions of the North Sea with distinct environmental processes governing species abundance: one north of Scotland, another east of Shetland, and a more southerly group (i.e. east of Scotland and west of northern Denmark). Impacts by jellyfish are likely to vary regionally, and ecosystem management may benefit from considering this spatial variability.

A study of the dissolved inorganic salts of nitrogen, silicon, phosphorus and carbon and their particulate forms in the Bristol Channel (Abdullah, Dunlop & Gardner, 1973) has shown that the primary sources of these elements are run-off and waste disposal. Furthermore, the slow flushing rate of the Channel plays an important role in the accumulation of these materials in the eastern part. An important constituent of run-off is the heavy metal load especially in industrial waste. Some preliminary investigations (Abdullah, Royle & Morris, 1972; Butterworth, Lester & Nickless, 1972; Nickless, Atenner & Terille, 1972; Preston, 1973) have shown that certain trace metals such as Cu, Pb, Cd, and Zn are added to the Channel in sufficiently large quantities to produce high concentrations not only in the waters of the Severn Estuary and Swansea Bay, but also in the local fauna.

An earlier paper (Holme, 1961) described the bottom fauna off the south coast of England, as sampled by a modified anchor-dredge. Sampling was later extended to cover the whole English Channel, a further 144 stations being worked, making 311 in all. This paper describes the results of the later survey which, as previously, was concerned mainly with molluscs and echinoderms. Distribution charts for the majority of species identified are given, in which are incorporated the results of both surveys.

Late stage juveniles and adults of Callinectes sapidus in Chesapeake Bay, USA, and Maja squinado off the Ria de Arousa, Spain, were compared for ontogenetic changes in movement patterns (speed, distance, orientation) and habitat selection (depth, substrate) using ultra-sonic telemetry and published information. After settling in submerged grass beds in the lower Bay, 20-mm juvenile C. sapidus disperse long distances into low salinity sub-estuaries to feed and grow to maturity in two years. Within the Rhode River sub-estuary, juvenile C. sapidus moved with a mean speed of 12 m h1 in nearshore shallows (1·1 m); whereas adults averaged 24 m h·1 in the deeper (2·9 m) channel areas and moved freely in and out of the main estuary. Individuals of both life stages exhibited a pattern of slow meandering (juveniles, 2 m h1, adults 10 m h·1) within a limited area, alternating with faster, directionally-oriented movement (both stages >50 m h·1) between meandering sites. Juvenile and adult males over winter in deeper water nearby, while inseminated females migrate long distances into high salinity areas to incubate the eggs. Callinectes sapidus completes the migration cycle only once per 2·5-y generation. Maja squinado settles on rocks in shallow kelp forests in the coastal zone, where they grow to maturity in 2 y. Juveniles moved slowly (0·5 m h·1) while meandering without directional orientation on shallow (4 m) small patch reefs during summer. After the pubertal moult in summer, adults also meandered slowly (1 m h·1) mostly on rocks at slightly greater depth (7 m). In late summer and autumn, newly mature and older adults moved with directional orientation into deeper (10·40 m) water for the winter, until migrating back to the shallows for the summer; whereas juveniles remained inshore on rocks for the winter. Adult M. squinado live several years after puberty and complete the seasonal migratory cycle several times during their lives.

The behavioural experiments described in this paper were carried out to complement earlier physiological work on the acoustico-lateralis system of the clupeid fishes. Previous work, summarized by Blaxter, Denton & Gray (1981a), has shown that the sense organs of the clupeid utriculus are highly sensitive to alternating pressures. Since the utriculus signals the polarity and amplitude of each peak in a complex pressure wave form separately, independently of the rate of change of pressure over a range equivalent to a frequency band of 30–800 Hz, it is well suited to give information on brief noises. In the clupeids the lateral line is hydrodynamically connected with the ear and we have suggested that the signals arising from the inner ear and the neuromasts of the lateral line are used in conjunction to provide information about direction and range.

Annual surveys carried out in south-west England since 1949 show that the arctic-boreal barnacle, Balanus balanoides, which was uncommon or rare in i960, has increased greatly in abundance during the colder years since then. Its numbers now approach those recorded in the 1930's, and there has been a corresponding reduction in abundance of the warm-water species, Chthamalus stellatus.

The reflected patterns and colours of terrestrial animals often show a sexual dimorphism associated with visual display, mate recognition and selection. In the sea the structures associated with bioluminescence may also show a marked sexual dimorphism. Some apparent bioluminescent dimorphisms (e.g. differences in photophore numbers) are probably secondary functions of sexual differences in size. A role in sexual communication is much more likely where specific photophores are developed or enlarged in mature specimens of one sex only but the presence of light organs in female anglerfishes (but not in males) is complicated by a significant size dimorphism. Dimorphisms in dragonfishes and lanternfishes primarily involve the relative enlargement of particular photophores in the males. A sexual role is assumed, but the morphological differences are often small. Most male ponyfishes have enlarged light organs; behavioural observations of free-swimming animals have clearly demonstrated that the males use them to generate bioluminescent sexual signals.

A study was conducted between 1997 and 1999 to investigate meiofauna assemblages from selected inshore and offshore locations around the UK coast. The main objective was to relate the differences in meiofauna distribution patterns to a number of measured environmental variables and to establish more clearly the sensitivity of meiofauna communities to anthropogenic disturbance. Results from univariate and multivariate data analyses show that distinct spatial differences in species distribution patterns exist and that these correlate with the natural physical characteristics and concentrations of trace metals in the sediment. Abundance and diversity of meiofauna assemblages were generally higher offshore than inshore and this difference can be attributed to both natural processes and anthropogenic impacts. The inclusion of meiofauna in applied monitoring programmes offers the potential for improving the resolution of the spatial extent of anthropogenic impacts over that achievable from macrofauna investigations alone.

Meiobenthos, here defined as metazoans passing through a ½ mm screen, is described from core samples collected on muddy grounds at 100-140 m depth in the North Sea and off the west coast of Scotland between February 1962 and August 1963.

Sixteen cores of 2·2 cm diameter were collected from Loch Nevis, and 14 from the Fladen ground. The top 7 cm of each core was passed through a 500μ then a 76μ screen. The residues were examined entire, and the nitrate of the finest mesh was subsampled.

The fauna consisted mainly of nematodes, kinorhynchs, ostracods, copepods, polychaetes, and lamellibranchs. Between 61 and 97 % of the population consisted of nematodes, but copepods were second in importance and were more abundant than recorded on other subtidal grounds.

The fine mesh (76μ) retained almost all specimens of every animal group except Nematoda. Numerically 38% of the nematode population passed through the fine sieve, but this represented only 18% by weight.

The mean dry weight of meiobenthos on Fladen was calculated as 0·76 g/m2 and the average number of individuals was 196 × 104/m2.

In Loch Nevis the corresponding weight was 1·28 g and the number 101 × 104. The loch had a larger and more varied population of all groups except nematodes, which were particularly abundant on Fladen.

The data do not indicate significant population fluctuations throughout the year in the permanent meiobenthos.

Compared with other subtidal grounds Nevis and Fladen seem to support much richer populations, and the high values for Fladen are of particular interest since this is a poor macrobenthos area.

An attempt is made to indicate the possible level of meiobenthos productivity and it is suggested that there may be competition between meio- and macrobenthos for available organic matter which could result in a less efficient production of fish food.

During the austral spring (December 1996), numerical abundance of copepod species (Crustacea: Copepoda) was estimated from 53 sampling stations scattered over the coastal waters off Mejillones Peninsula, northern Chile. Samples were obtained from two depth strata; 0-50 m and 50-200 m depth. Oceanographic data over the three-day cruise indicated that coastal upwelling was actively occurring during the survey.

A total of 19 species was identified, of which four of them, Paracalanus parvus, Oncaea conifera, Oithona similis and Calanus chilensis, accounted for more than 80% of the whole copepod assemblage in terms of numerical abundance. Using the K-means exploratory analysis the 53 locations were grouped into two clusters: an upwelling type and a non-upwelling type. The former characterized by locations nearshore, with low temperature (<17°C) and high chorophyll-a (>13.4 mg m−3), while the latter had warmer waters (>18°C) and low chlorophyll-a (<4.8 mg m−3). Chlorophyll-a (chl-a), distance to shoreline and temperature at 10 m depth (T10) were all significant variables ( P<0.05) for clustering analysis. There was a strong negative correlation between T10 and chl-a ( P<0.01). The same clustering technique, based on species abundance, suggested the presence of a unique cluster, whose composition was dominated by P. parvus, O. similis, Acartia tonsa and Centropages brachiatus. Stepwise multiple regression showed that these species were also strongly correlated to chl-a and T10. Together these analyses suggest that water mass circulation during upwelling is the driving force for structuring spatial patterns of copepod distribution. In addition, a vertical distribution parameter suggested that copepods, independently of time of the day, tended to remain in a large proportion in near surface waters, possibly constrained by a shallow oxygen minimum layer. This implies that advection during active upwelling may cause large fractions of populations being transported offshore, allowing zooplankton export to more oceanic waters. Rapid turnover rates of copepods growing continuously year-round, may act as a mechanism to compensate population losses during persistent coastal upwelling.

The magnitude of geographical variations of stable isotope ratios of carbon and nitrogen was examined in ten squid species captured in seven areas of the world's oceans. The average of all 139 squid was −17.4±1.4‰ for δ13C and 11.6±1.6‰ for δ15N. The δ13C of squid showed a clear-cut negative correlation with the latitude of the sampling locations, reflecting the well-known latitudinal characteristics of phytoplankton δ13C, while squid δ,15N did not correlate with the latitude significantly. The δ15N reflected the regional characteristics of nitrogen metabolism such as denitrification and N2 fixation, and it was conspicuous in the intraspecific variation in Sthenoteuthis oualaniensis ranging from 10.0±1.5‰ off Japan to 16.3±0.6‰ off Peru in the Pacific Ocean. Significant isotopic variations were also found in the local area among the five species off Japan in the Pacific Ocean and among the three species in the Japan Sea. Attention must be paid to the isotopic variations of primary producers as well as those of squid in examining the trophic positions of squid.

This review examines the biology of the two main cockle species Cerastoderma edule and C. glaucum found in coastal areas around the north-east Atlantic from Norway to Morocco and through the Baltic, Mediterranean and Black Sea. It considers those factors in particular that impact on the overall health and survival of individuals as well as populations. Methods for the discrimination of the species are reviewed as well as the approaches being taken to delineate different populations, which is crucial to appropriately manage individual fisheries. Cockle populations generally undergo sexual maturation during their second summer and sexes are separate. Eggs are pelagic, with larvae being both benthic and pelagic before settling on the sediment and becoming benthic adults. However, data are lacking on basic larval biology and dispersal mechanisms. Data are provided on predator–prey relationships including information on types of food of importance to cockles. Main predators of cockles include brown shrimp, shore crabs, gastropods, polychaetes, fish and a variety of birds and these can be important in structuring cockle populations. Predation of larval cockles by adult cockles through larviphagy can lead to reductions of up to 40% of the population. Cockles are sensitive to a wide range of chemical contaminants but few data are published on impacts on cockles, in particular larval stages. The review concludes with an assessment of future climate change scenarios on cockles and considers some areas of future research required to preserve this ecologically and economically important species.

The Crustacea play an important economic role in the marine and aquatic environments not only as a food source but also in the productivity of the fisheries. Exploitation of these resources has led to a need for intensive culture methods which impose physiological stress on the animals and consequently increase the incidence of disease. The need to reduce the lethal and debilitating effects of pathogens has stimulated a renewed interest in the defence mechanisms of the Crustacea.

Experiments on yolk utilization were done with developing herring eggs and larvae from races spawning in the Clyde, North Sea, Atlantic and Baltic. The range of mean dry weight of unfertilized eggs varied from o·126 to o·366 mg in the different races.

The use of natural plankton and other foods, and of transfer techniques during phases of mortality before metamorphosis, has made it possible for substantial numbers of herring larvae to be reared beyond this stage, thus supplying requirements for experimental work. A survival to and beyond metamorphosis of over 10% of larvae passing the yolk-sac stage (3–4% of hatched larvae) has been obtained.

INTRODUCTION

The problems involved in the identification of freeliving marine nematodes have stood in the way of ecologists for some time. Although considerable advances are now being made on the continent (particularly in Kiel Bay and the Mediterranean) and in North America, our lack of knowledge of the British species is still lamentable. In order to rectify this state of affairs to some extent, a study of the distribution of nematodes in the Exe estuary was planned to cover as wide a spectrum of physical and chemical conditions as possible, ranging from fine muds with a low interstitial salinity at the head of the estuary to coarse sands with a high salinity at the mouth. It is hoped that the characterization of the fauna of various habitats in the estuary will form a basis for further ecological studies in other areas. Not surprisingly, a large proportion of the species found were new British records, and some new to science. The fourteen species of this latter group discussed in this paper are described elsewhere (Warwick, 1970).