Unusually high densities of juvenile flatfish in some areas of a nursery ground, and complete absences from other areas, were associated with a dense bloom of the colonial alga Phaeocystis pouchetii along the coast of North Wales. A possible explanation for these movements, and for the presence of patches of anoxic sediments, is proposed.

In this study the selachians were captured monthly on inshore grounds (10–30 m deep) with a beam-trawl over ten years (1975–1984), mainly in the Bay of Douarnenez, the Roads of Brest and the Bertheaume Cove area (west Brittany). Catches were composed of five species, accounting numerically for 6–5% of the mean catch of the trawled fishes, but reached up to 20% in Bertheaume Cove. On account of the adaptability to different bottom substrates Raja clavata is the most common species. Raja microocellata is uncommon except in the Cove of Bertheaume where it represented half of the selachian biomass captured.

The population structure of the thornback ray, Raja clavata L., expressed in terms of length and sex, seems to be related to hydrological conditions prevailing on the sampling areas. In the exposed area (Cove of Bertheaume), females are more frequently captured than males, and indeed represent the entire catch in the summer. In contrast, in the relatively sheltered area (Bay of Douarnenez) a majority of adult males and immature females are caught.

After winter, only adults and juveniles of Raja clavata migrate into the Bay of Douarnenez. This bay may be a mating area for adults and also a nursery for juveniles particularly for immature females.

Prior to moulting, the preadult Lepeophtheirus pectoralis produces a temporary frontal filament which attaches the animal to the surface of the host during ecdysis. This filament is extruded from a frontal organ previously thought to have a chemoreceptory function. During ecdysis the exuvium splits at the anterior margin and is shed posteriorly by contractions of the body. After hardening of the exoskeleton the copepod detaches itself from the frontal filament and is free-living on the host during intermoult. Males in precopula position hold on to the dorsal side of the female, with the second antennae grasping the anterior end of the female's genital complex. During the ecdysis of the female, most males release their hold on the female, and are usually found close to her on the host. Copulation occurs between an adult male and an adult female with a hardened exoskeleton. In the copula position the male holds on to the female's genital complex with the second antennae, but now on the ventral side of the female. Two spermatophores are extruded and then transferred simultaneously to the female with the aid of the second pair of swimming legs. Tubes originating from the spermatophores connect them to the orifices of the receptaculum seminis. These tubes seem to grow out of the spermatophores after expulsion. After copulation, the male retains a precopula position before releasing the female. No agonistic behaviour has been observed between a precopulating/copulating male and additional males. However, during the ecdysis of the female, a new male may take over the female, but mating does not seem to be assortative for size in Lepeophtheirus pectoralis.

The distribution of intertidal isopods with respect to algal species was investigated over a range of 250 km on the shores of north Spain. A survey of 25 localities included three zones with a distinct composition of algal species: a western zone comprising shores facing Atlantic waters and the outer part of the Bay of Biscay; a narrow transition zone (about 70 km in length); and an eastern zone extending to the inner part of the Bay of Biscay. Thirty two isopod species were collected, 11 of which were present in high densities. Response to geographical change was observed to occur clearly in three species, Ischyromene lacazei, Idotea pelagica and I. baltica, and to a lesser degree in I. granulosa; the former two and the latter two were abundant in the eastern and western zones respectively. All four species were found to be closely associated with macroalgae species which display geographical changes in abundance (e.g. Laminaria ochroleuca and Comllina elongata). In addition, Idotea species were found to inhabit a reduced number of algal species compared with other European shores. Spanish shore of the Bay of Biscay probably constitutes the geographic limit of the distribution of the four species. A sampling artefact might also be responsible to some extent for the patterns of distribution observed. Differences in the physico-chemical properties of sea water along the coast and circulation of coastal waters are not thought to influence the distribution of isopods.

The skeleton and calicoblastic ectoderm of the scleractinian non-zooxanthellate coral Caryophyllia smithii were investigated by light microscopy, scanning and transmission electron microscopy. Except for some costal spines, the skeleton was fasciculate. Fasciculi were made up of bundles of crystalline needles, each crystalline needle consisting of a number of linear series of small (<1 μm) rounded crystals. Fractured skeletons showed the fasciculi to be arranged into layers and that within some septa, theca and costal spines there were spaces that contained neither mineral nor organic matter. These spaces could also be found at the growing edges of septa and theca. Demineralization of the skeleton revealed an organic matrix whose configuration mirrored the architecture of the skeleton. In areas of the skeleton where deposition was occurring the overlying calicoblastic ectoderm was relatively thin with prominent intercellular spaces and secretory vesicles. In contrast, over non-depositing areas the calicoblastic ectoderm was thick and contained residual bodies, nematocysts and membrane-bound granules. The results are compared and contrasted with those from scleractinian corals that have endosymbiotic zooxanthellae.

Post-larval specimens of Hirundichthys affinis are capable of jumping out of water, but the pectoral and pelvic fins are not extended when in air. Penetration through the air/ water interface demands a force to overcome surface tension which is similar in magnitude to the force required for the jump itself. However, post-larvae do not produce the single propulsive tail flick which powers the jump until most of the animal has passed through the interface. The post-larva emerges at an angle close to 45°, thus maximising the horizontal distance travelled before re-entry.

Whether swimming slowly (4 body lengths s-1), or at maximum speed (36 body lengths s-1), post-larvae swim with the pectoral and pelvic fins extended. Calculations show that fast swimming post-larvae operate at Reynolds’ numbers of about 4×103, where surface roughness and projections decrease rather than increase drag.

The spawning, larval development, and postlarval characteristics of Calliostoma granulatum have been described and illustrated from laboratory observations. Spawning in this species does not follow a seasonal pattern, since adult specimens caught at all times of the year released viable gametes after two or three days in tanks. Eggs had a mean diameter of 341 μm and were surrounded by a mucous sheath by which they were agglutinated into ribbons of variable length that formed amorphous clumps on the bottom of the tanks. The veliger larval stage was short (two days) and took place inside the egg membrane. Development was direct, and at 18–19°C juveniles emerged as crawling young four days after fertilization. Larval and postlarval shells were studied with the aid of a scanning electron microscope.

Juvenile and adult two-spot gobies, Gobiusculus flavescens (Fabricius), were collected at three sites in the Plymouth area: the Plymouth Breakwater, Fort Bovisand, and the Yealm estuary. Fish were sampled by a diver-held grab-net, boat-towed zooplankton net, and beam-trawl, from early June until the end of September 1987.

Percentage abundance and percentage occurrence dietary data are presented by a graphical technique, such that prey importance (rare or dominant) and fish feeding strategy (specialist or generalist), is visually apparent. It is applied to the different size groups of fish from each site.

The mobility and quantity of retinula cell proximal screening pigment, and the liability of the eyes to light-induced damage, were investigated in the Norway lobster, Nephrops norvegicus (L.), obtained from three separate populations from depths of 18, 75, and 135 m.

During the morning after capture, the migration of the proximal pigment in response to the onset of illumination below the threshold for damage varied between the three populations. In the eyes of deep water N. norvegicus, the proximal screening pigment was located close to or below the basement membrane when dark-adapted and rose to a position midway up the rhabdoms when light-adapted. In the dark-adapted N. norvegicus from shallow water the proximal pigment was located more distally than in eyes of deep water animals. After the onset of illumination, the pigment migrated distally to completely cover the rhabdoms. The amount of retinula cell proximal screening pigment was found to decrease linearly with depth.

When dark-adapted individuals from each depth were exposed to light a positive correlation was obtained between the photon fluence rate (PER) and the proportion of the retina damaged. For a given light exposure the amount of damage was highest in animals from deeper water. The PFR causing 25% damage was approximately 1 log unit higher in animals from 18 m compared to those from 135 m.

The amount of damage varied with the delay between capture of the animals and exposure to light. When exposed 2 h after capture significant differences between depths were seen but the results were influenced by the incomplete dark adaptation of some specimens.

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).

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.

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.

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.

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.

Whole flounder serum has been fractionated by gel filtration on Ultrogel AcA22. Pooled material from the first major peak of the elution profile was further fractionated by FPLC ion-exchange chromatography and this yielded one major and three minor peaks. Under both reducing and non-reducing conditions SDS electrophoresis showed that the major peak and two of the minor ones were immunoglobulin (Ig). All three of these Ig populations were tetrameric, with estimated molecular weights of 710 kD. However, approximately 90% of the major Ig species consisted of tetramers which were covalently linked by disulphide bonds, whereas the remaining 10% was composed of dimeric molecules held together by non-covalent interactions. The heavy chains of all three Ig populations had apparent molecular weights of approximately 72 kD but the light chain composition showed considerable heterogeneity. In the major population, five polypep-tides were detected in the light chain region of the gel with apparent molecular weights covering the range 22–28 kD. However, there was no difference in the light chain composition of covalently and non-covalently linked tetramers. The two minor populations differed both from each other and from the major species in respect of their light chain compositions. No evidence was found for a monomeric serum Ig, and alkaline urea electrophoresis failed to demonstrate a J chain.

The age and growth rate of Modiolus modiolus have been studied from acetate peel replicas of polished and etched shell sections. Age estimates could be reliably obtained from the alternating patterns of light (summer) and dark (winter) growth lines present in the middle nacreous layer of the shell. Growth lines in the inner nacreous layer, however, generally converged to form blocks of nacre such that the identity of individual lines was lost, whilst in the umbones growth lines were often tightly compressed and difficult to resolve. Data obtained from analyses of the internal growth lines in the middle nacreous layer were used to construct growth curves for several subtidal populations using the von Bertalanffy growth equation. The fastest growth rate was recorded for mussels growing epifaunally on the legs of a drilling platform in the North Sea; these mussels achieved a maximum shell length of 110 mm within ten years. The oldest mussel (from Ling Bank in the northern North Sea) was 48 years old and measured 133 mm in length whilst the largest mussel (from Loch Spelve in western Scotland) was 147 mm long and 38 years old. With the exception of the relatively young population (maximum age 10 years) from the drilling platform, most of the benthic populations studied included mussels in excess of 35 years of age. It is clear, therefore, that M. modiolus is a potentially long-lived member of the subtidal benthos.

Thirty-four adult individuals of Loligo forbesi (males and females with dorsal mantle lengths from 27–77 cm) were observed in captivity in a 3 m diameter closed sea-water system on Faial Island, Azores. Squids were caught by jigging and were fed with horse mackerel (Trachurus picturatus) and chub mackerel (Scomber japonicus), either alive or dead. The maximum survival was 73 days. Feeding behaviour was dependent upon both the size of prey and its state of preservation;e.g. the squid would eat the head of small fish (< about 15 cm), reject the head of medium-sized fish (about 15–35 cm) and would eat only the dorsal part of a big fish (> about 35 cm) or a fish poorly preserved.

Seventeen chromatic, 9 postural and 6 movement components of body patterns were observed and described. Conspecific interactions considered to be aggression and dominance were observed among males; no such interactions occurred when one male and two females were kept together. Body patterns in relation to relaxation, stress, shock, feeding, locomotion and aggression are also described.

During the summer months of 1983 Prorocentrum minimum (Pavillard) Schiller, not earlier recorded from the Adriatic, constituted a considerable proportion of the regular summer bloom in the Sibenik Bay (eastern Adriatic coast). During the subsequent years (1984,1985,1986) the proportions of P. minimum in summer blooms in the Ŝibenik Bay was constantly increasing (Marasović, 1986; Marasović, in press). At the same time its presence was reported from the other parts of the Adriatic coast, attributed to the intensified eutrophication of the Adriatic waters (Pucher-Petković & Marasović, 1987; Marasović et al., 1988; Pucher-Petković et al., 1988; Marasović, 1989).

A comparative study of the state of preservation of hydromedusae has been made based on a collection that has been preserved for 80–90 years. A report has been compiled in tabular form concerning the state of the collection in relation to the present pH of the preserving fluid. Recommendations are made based upon which fixative and preserving fluids have proved to be best for long-term storage.