Ovaries of the common sole (Solea solea (Linnaeus)) were collected prior to, or at the beginning of, spawning from the spawning grounds in the Bristol Channel. Size frequency distributions of oocytes over 100 μm are presented. They clearly show a break in the size frequency distributions, at about 170 μm, indicating that the production of new oocytes to be spawned that season had ceased. It indicates that the sole is a determinate spawner and that, at least for this population, an annual potential fecundity can be measured. Estimated annual fecundity at length of Bristol Channel sole is calculated, and values are compared with those found for sole from the North Sea, eastern English Channel and the Bay of Biscay.

The larval shell of molluscs contains a preserved record of the organism's growth and developmental history. Many investigators have utilized the information recorded in the larval shell morphology to infer mode of development.

Marine prosobranch gastropods were collected from intertidal sites from Maine to Florida and were cultured in the laboratory. Scanning electron microscopy was used to document the relationship of larval shell morphology to development. Four species with planktotrophic larvae, Crepidula fornicata, Crepidula plana, Cerithium atratum and Ilyanassa obsoleta, and four species with non-planktotrophic development, Crepidula convexa, Littorina obtusata, Busycon canaliculatum and Urosalpinx cinerea, were successfully reared through metamorphosis.

The Tikehau atoll (Tuamoru Archipelago, French Polynesia) is located at 14°S 148°W. Phytoplankton and sand microalgae are the most important primary producers of the lagoon. They were studied for 4 years.

The relationship between light energy and lagoonal primary production was measured by using the 14C method for phytoplankton and O2 method for phytobenthos. Incubations, carried out in situ, were made at different depths and light exposition times.

Irradiance was high and 17% of the light energy measured at the surface reached 25 m (lagoon average depth). Maxima of phytoplankton and phytobenthos productions occurred at low depths; there was therefore no photoinhibition of photosynthesis. Correlations between light energy and primary production were strong, especially for phytobenthos. Multiplicative linear regression models (production vs light) associated with an exponential linear regression model (light vs depth), allowed planktonic and benthic primary production to be predicted from the depth and the light energy received at the surface. The benthic primary production exceeded the phytoplanktonic production in the upper 18 m. The total primary production (benthos + plankton) was constant with depth and depended only on light energy at the surface. One Einstein received at the lagoon surface allowed the growth production of 14 mg of carbon (water column + sediments).

The swimbladder is recognized as responsible for a major part of the acoustic backscattering from fish. In most fishes it has the function of a buoyancy regulator but in others its main function is rather unclear. Based on methods for exact mapping of the swimbladder shape, observations of deviations from normal appearance and shape are discussed in relation to possible effects on target strength. Evidence for both periodic variations, as from uncompensated vertical migrations, and seasonal variations, caused by the fat cycle and gonad development, are presented.

Artificial substrates were used to monitor Mytilus edulis L. settlement on an exposed rocky shore at Ballynahown, on the west coast of Ireland, from August 1984 to September 1985. Flat nylon domestic pan scourers proved to be good collectors of mussel recruits. The appearance of new modes of 300 µn shell length at times of increasing density of colonising mussels indicated direct settlement of mussel larvae from the plankton onto the pads. These modes appeared in September 1984, May 1985 and August 1985. Direct settlement periods followed the known main spawning times of adult mussels at the study site, March-April and July-August, and are consistent with settlement times ob-served on filamentous algae and adult beds on the same shore. Results from the study show that mussels of primary settlement size, 250–400 im shell length, were available to colonise newly deployed pads throughout the investigation. Furthermore, cohorts of larger mussels recruited to the pads during much of the year. The possible source of these recruiting mussels is discussed.

Hermit crabs use gastropod shells to protect their bodies and developing eggs; an inadequate supply of shells of the appropriate size will, therefore, adversely affect their growth, fecundity and longevity. Since the supply of shells is commonly limited, mechanisms that help to reduce these adverse effects will be selectively advantageous. In Pagurus bernhardus it is suggested that two mechanisms have evolved in this respect: larval settlement is encouraged in the littoral zone where gastropod species are diverse and numerous and where the youngest hermits will find growth potentially unrestricted; and females breed within their first year of life and at a size substantially below that which could be attained in the shells commonly available to them. This ‘precocious’ breeding is suggested to be an adaptation enabling hermits to overcome the problems of shell-limitation, since it frees females of the need to attain a specific age or size before reproducing - a situation which would be perilous when large shells are scarce. Males of a similar age are freed from competition for the larger shells as a result of this strategy, since the growth of the females is suppressed while they are ovigerous.

In constant conditions, freshly-collected Lipophrys pholis show an endogenous circatidal activity rhythm, the initial activity peaks of which are phased to the expected time of high tide. The rhythm usually damps out over a few days but it may re-appear spontaneously or as a result of disturbance caused by handling and transfer to the experimental apparatus. The free-running period is more variable in fish kept in non-tidal conditions for prolonged periods than in those recorded shortly after capture. The non-circatidal periodicity shown by some fish may be the result of stable coupling in antiphase of desynchronised oscillators. There is no semilunar variation of the circatidal rhythm and no influence of the slight diurnal inequality in tidal period upon the rhythm's periodicity, at least at the site studied. The activity rhythm of Lipophrys varies seasonally.

Imposex (the development of male sex organs on the female) has been studied in the European sting winkle, Ocenebra erinacea. In common with studies of other gonochoristic stenoglossan gastropods, the evidence gained from surveys of the south-west regions of England and Brittany (France) indicates that the phenomenon is a response to tributyltin (TBT) pollution. Close to sources of TBT, O. erinacea females exhibit structural abnormalities of the oviduct as a result of advanced imposex, including absence of a genital papilla and a normal vulva, a deformed bursa copulatrix and the presence of a longitudinal split. Copulation and capsule formation would appear to be inhibited in the worst-affected females. Such curtailment of breeding activity would result in population decline: direct evidence of the extinction of O. erinacea close to harbours, as is known for N. lapillus, is generally wanting for British shores, but the decline of the species in the Bay of Arcachon in France is attributable to TBT pollution.

Serological methods for prey identification have been applied to detection of residues of sandeel (Ammodytidae) protein in faeces of common seals (Phoca vitulina) and grey seals (Halichoerus grypus) from the Moray Firth, north-east Scotland. Antisera raised to muscle protein from Ammodytes marinus were evaluated by testing their reactions with protein extracts made from a range of North Sea fish species and protein residues in in vitro digestates, seal digestive tracts and seal faeces. It was concluded that, using fused rocket immuno-electrophoresis, linkage of precipitin peaks from unknown samples with peaks from standard sandeel extract was a reliable indicator of the presence of sandeel in the unknown sample. Seasonal variation in the incidence of sandeels in common seal diet in the Moray Firth was examined by identifying otoliths, bones, and proteins, and all three methods indicated that sandeels occurred in the majority of samples tested in the summer, but were less important during the winter. Proteins were detected in fewer samples than otoliths, particularly in February and March. Possible reasons for this difference are discussed. Serological identification of sandeel proteins is potentially applicable to dietary studies on all marine predators.

The swimming behaviour of Corophium volutator from Wales and East Anglia was investigated to establish whether differences apparent from two previous studies are real or artefacts of the different techniques used. Swimming C. volutator were caught in a Welsh estuary in the summer, but only rarely in the autumn and winter, and in both daylight and darkness. In simulated tidal conditions in the laboratory C. volutator from two sites in East Anglia never swam, while those from Wales swam whenever the substratum was immersed, in daylight and darkness, mostly on the ebb tide and in winter. The unnatural swimming in winter may have been stimulated by laboratory conditions, but the East Anglian amphipods were not so affected. The tidal swimming rhythm is different to east coast C. volutator which only swim at night. This difference may be related to the time of spring tides, when most swimming occurs. In Wales high water of spring tides may occur only in daylight in summer and nocturnal swimming may not be possible. The ebb tide swimming by C. volutator in Wales contrasts with the flood and ebb swimming of east coast amphipods and may reflect differences in their habitats. The former were collected close to the sea while the latter were 15 km up a narrow estuary and may represent a sub-population of amphipods with a disposition to swim early (on the flood tide) enabling them to colonise upstream habitats.

An account is given of a flagellated protist isolated from Atlantic sediments at a depth of 1500 m. The organism forms part of the microbial food web by consuming suspended bacteria. The organism was originally described by Ruinen as Cryptobia libera. On the basis of its ultrastructure, assignment to the genus Cryptobia is regarded as inappropriate, and Jakoba is proposed as a new generic vehicle.

Lissarca notorcadensis, a small pallial-brooding mollusc with a circum-Antarctic distribution, is frequently found attached by stout byssal threads to the spines of sea urchins. Here, complete ontogenetic series can be found. Using standard, structural definitions, the prodissoconch I of L. notorcadensis is small compared to the large prodissoconch II, a feature atypical of brooded young and possibly reflective of a planktotrophic past. Fine commarginal striae are found on prodissoconch II of this subtidal clam, which also possesses more pronounced commarginal striae on the dissoconch prior to brood release. The provinculum is retained and remains functional well into adulthood. A small central ligament pit is present through the postlarval stages. This develops into a large, triangular pit in adulthood that shows obvious growth lines. Calcareous, presumably aragonitic fibres develop in the ligament of specimens still retained in the adult brood. Five to six adult hinge teeth are formed on either side of the ligament. Alignment of shell valves by these well-developed teeth is augmented by retention of larval denticles. The functional and structural demise of the provinculum occurs between 4 and 7 mm shell height and results from denticle erosion and subumbonal shell overgrowth. Many canals permeate larval and adult valves, but external pores in the adult shell differ from those of the larval shell and could indicate mode of formation. Prodissoconch form, provinculum retention, and shell canals are considered primitive traits.

Tanning of the Raja erinacea egg capsule occurs after secretion of capsule precursors from the nidamental gland and involves the introduction of catechols and their subsequent oxidation to quinones by catechol oxidase. At the time of secretion and assembly of capsular precursors in the nidamental gland, the capsule is white, contains no catechols and lacks chemical and mechanical stability. Following formation in the nidamental gland, catechols accumulate in utero in parallel with colour development. An inactive form of catechol oxidase is incorporated in the capsular matrix at the time of secretion. Catechol oxidase activity increases concomitantly with increasing catechol content and colour development.

Adult plaice (Pleuronectes platessa L.) in the southern North Sea use selective tidal stream transport to migrate between their summer feeding grounds and winter spawning grounds. The fish come up into midwater when the tidal stream is flowing in one direction, but remain on the bottom when it is flowing in the opposite direction. This behaviour can theoretically save energy, which can be used for growth or reproduction. Alternatively, it may provide a transport system by means of which fish that have no ability to navigate over long distances can be conveyed reliably between their feeding grounds and spawning grounds.

Doliolids were found in samples taken with a Continuous Plankton Recorder (CPR) in October 1989 between 55°14'N 03°32'E and 55°20'N 06°13'E during a tow between Newcastle and Esbjerg. Densities were estimated at >100 m−3 for about 112 km of tow. A sub-sample of specimens in sufficiently good condition to be reliably identified were referred to Doliolum nationalis Borgert. Substantial numbers of doliolids were found on a CPR tow between Harwich and Gothenburg which passed through the same area in that month and specimens were found nearer to the Danish coast in November and south-west of Helgoland in December. The distribution of doliolids in CPR samples taken in the North Sea in the last three months of 1989 is shown in Figure 1.

Slope currents in the Bay of Biscay show a consistent poleward transport but seasonal trends and vertical current structure appear more variable. Indeed more long term records are required to establish seasonal trends firmly.

In the south of the region (Spanish slopes, mooring 118), the upper-slope (water depth 1005 m) flow exhibited a strong vertical structure with the maximum surface inflow occurring in the winter period, and this effect may be wind induced. Satellite imagery shows that this flow originates from the Iberian slope and that a decreasing along-slope surface transport occurs along the north Spanish slopes at this time of year.

In the north of the region (Porcupine Seabight slopes) vertical structure was again evident in the upper slope (~1000–m depth) flow. At mooring 114 the flow at mid–depth showed a weakening along-slope flow and an on-slope tendency in the March/April period; a complete reversal in the slope current occurred at mid–depths at the position of mooring 112 during March.

In the central region (Celtic and -Armorican slopes) seasonal variations in the upper layers on the slopes were also present. In this region, the upper–slope transport (2500m depth) reached maximum values of 3–5 Sv in late summer. Upper flows at the rise (mooring 8002) were directed on-slope during the period of maximum upper–slope transport but changed direction in the March/April period.

In this region on the Celtic shelf (DB1), the surface flow is in a counter–current sense and wind-induced and so the seasonal variations here reflect seasonality in the wind stress.

Herring (Clupea harengus L.) larvae, ranging from 8–35 mm T.L. were subjected to predation by juvenile herring and sprats (Sprattus sprattus L.) ranging from 80–160 mm T.L. Responses to attacks and non-threatening encounters were recorded by a TV system operated with infra-red light, which was invisible to both predator and prey. Records were made in both light and dark with larvae before and after the otic bullae filled with gas, before and after lateral line canal formation, and before and after chemical ablation of the neuromasts with streptomycin.

Larvae often responded with a C-start, turning away from the stimulus source, both in dark and light. Attacks on larvae occurred only in the light. Responsiveness to attacks was very low in the smaller larvae but increased as the otic bulla filled with gas and the lateral line canal developed. Larger larvae responded more often to attacks than to non-threatening encounters with predators. Vision seems to inhibit unnecessary responses since responsiveness was lower in the light than the dark for non-threatening encounters. Response distances were generally short, only 2–4 cm, with no substantial differences associated with sensory capability.

This ultrastructural investigation of gametogenesis in a deep-sea anemone of the Bay of Biscay trawled around 2000 m depth, contributes to the knowledge of biology and strategy of reproduction of deep-sea benthos.

This sea anemone is dioecious. The sperm appears very similar to those of shallow water sea anemones of the genus, Calliactis. The ultrastructural investigation of oogenesis allows the characteristics of the stages of previtellogenesis and vitellogenesis to be defined. The latter begins with a period of lipogenesis correlated with the formation of a trophonema. Mature oocytes measure up to 180 (im in diameter. Study of spermatogenesis and oogenesis reveals that spawning occurs in April/May. In males, the main area of testicular cysts, full of sperm, reaches maximal development from March to May and, in females, the percentage of mature oocytes decreases from 33% in April to 1% in May.

Spawning may be induced by the advent in the deep-sea of the products of the spring phytoplankton bloom. This period of spawning, during the increased deposition of organic matter to the deep-sea floor, may be an advantageous strategy for early development of Paracalliactis.