The assemblages of attached and freeliving epibenthic species in the North Sea are described, based on analysis of samples collected with a small beam trawl. Clustering of survey sites based on the presence or absence of attached species indicated that three regions had characteristic assemblages: the northern North Sea, the central North Sea from 55 to 57°N and the southern North Sea. Clustering of sites based on counts of free-living epibenthic species also revealed that the sites formed three major groups but these corresponded to regions in the north-east North Sea, the northern and western central North Sea and the southern and eastern central North Sea. Species which contributed most to the similarity within and dissimilarity between groups were identified. The environmental factors which best accounted for the grouping of sites were depth, winter temperature and the temperature difference between winter and summer for attached species and depth and the temperature difference between winter and summer for free-living species. The species richness of attached and free-living epibenthic species was higher in the central and northern North Sea than in the south. The number of abundant (Hill's N1) and very abundant (Hill's N2) free-living species also increased from south to north.

Polar benthic communities are subject to a range of disturbance levels from a variety of sources, principal amongst which is ice. This occurs in four main forms: the ice-foot, ice scour, anchor ice and fast ice, each of which influences benthos in a very different temporal and spatial manner. The four described forms of ice disturbance are all seasonal, but combined, influence communities throughout the year. The magnitude of ice mediated disturbance is often catastrophic and as a result both dominates benthic community structure and makes recolonization and development rates critical. This disturbance extremity results in high temporal and spatial heterogeneity, very low intertidal zone diversity and in places low mid–sublittoral diversity. It may also, however, be important in generating and maintaining the typically high sublittoral zone diversity observed at many polar localities. Intermediate frequencies or magnitudes of disturbance have been controversially discussed as important in maintaining diversity by prevention of space monopolization by overgrowth dominants in such environments as the deep sea. The shelf areas examined to date certainly suggest intermediate disturbance is important in maintaining polar sublittoral zone diversity. The combination of slow colonization and development with high frequencies of disturbance means most polar nearshore environments that have been described are permanently in a state of change or recovery.

In order to estimate the degree of implantation of excavating sponges in the oyster populations from the littoral zone at Blanes (north-western Mediterranean Sea), a representative sample of oysters (Ostrea edulis) was collected from depths between 0.5 and 4 m in 1986. All oysters were infested by the excavating sponges Cliona viridis and Cliona celata. Infestation affected always and exclusively the lower valve always reaching the inner side. The degree of infestation proved to be independent of oyster size and weight. Colonization by contact was considered the main means of dispersion of these sponges within the oyster population. Cliona viridis and C. celata emerged as the single excavating species able to effectively compete with other non-excavating or excavating organisms when trying to colonize the particular calcareous substrate provided by oyster shells in the north-western Mediterranean Sea.

Two strains of 6–8-y old Actinia equina (Anthozoa: Actiniaria) asexually derived from two individuals collected on the coast of Brittany were artificially UV irradiated in long-term experiments in the laboratory. After the animals had been allowed to adjust to the test aquaria for 15 months, a programme of UV irradiation and multiparameter analysis continued for 24 months. Ultraviolet irradiated sea anemones obtained in addition a quasi-solar UV irradiation at intensities representing the daily and annual cycles. Of the three modes of UV irradiation tested (1X, 2X and 4X), the one with the lowest intensity and duration (1X) corresponded approximately to the irradiation to which sea anemones are exposed in their natural habitat in the tidal zone of the southern North Sea. In all three modes all the actinians showed a similar, highly significant quasi-exponential weight loss immediately after the onset of UV irradiation. The more the animals were irradiated, the later juveniles were released from the gastrovascular cavity. At 2X the number of active animals gradually decreased after 18 months, whereas with the 4X irradiation mode the amount of activity fell abruptly and significantly after only eight months and remained at a very low level. Detachment from the substrate was also induced by UV irradiation. The experiments showed genotype-specific differences in body mass and migration. The crucial findings were that A. equina individuals that had adjusted to the laboratory for a long time did give clear responses to UV doses and intensities corresponding approximately to the irradiation in their natural intertidal environment or by radiation increased severalfold. The responses were immediate and sometimes irreversible to UV even in naturally occurring intensities and doses. The genotype specificity of some responses provides evidence that the stressor UV could induce genetic modifications of the population.

The influence of various species of digenean trematodes on the in situ growth rate of Littorina littorea (Gastropoda: Prosobranchia) from different habitats was investigated. The main results showed: (1) that infections either reduced or had no significant effect on growth in comparison with uninfected snails; (2) that the same type of infection could have a differential effect on growth depending on the habitat/population from which the snails originated. These findings are consistent with the life history hypothesis expecting no or a stunting effect of trematode infections on the growth of longer-lived snails, but do also emphasize that growth rates following trematode invasion can be significantly modified by environmental conditions, such as, food availability.

In this study the digenean parasites in the mud snail Hydrobia ulvae at two sites were compared for a period of one year. The sites were the north shore of Belfast Lough (Northern Ireland) and the Bend of Tarty on the Ythan Estuary (north-east Scotland). Samples of snails were collected monthly from which 13 species of digenean larvae were recorded at Belfast Lough. Two of these species were absent at the Bend of Tarty. Overall digenean prevalence was very similar at each site indicating that the respective bird communities were composed of ecologically equivalent species. Differences in the prevalence of individual digenean species are discussed in relation to the abundance of definitive and/or secondary intermediate hosts at each of the sites. Both sites displayed similar seasonal patterns of parasite prevalence with sharp increases to around 25% in the summer months. Snail shell heights were greater at Belfast Lough than at the Bend of Tarty and a positive correlation between snail shell height and infection by trematode parasites was recorded at both sites. Increased parasite prevalence in larger snails was attributed to factors such as age-related susceptibility and/or parasitic castration of the snails.

Spectral reflectivity and transmission of the iridescent cuticle of six species of male Sapphirina (Poecilostomatoida: Copepoda) were measured by microspectrophotometry. Sapphirina angusta and S. opalina showed two spectral peaks of reflection, one at about 420 nm and the other at wavelengths longer than 750 nm. Sapphirina auronitens and S. gastrica had dominant peaks at wavelengths longer than 500 nm. Sapphirina ovatolanceolata had peaks between 430 and 600 nm, while S. metallina had various peaks along a wide range of wavelengths. The peaks at the longer wavelength in S. angusta and S. opalina may be related to the red pigments in the subcuticular layer of the species, or a result of a second-order effect of the multilayer system. The spectra of transmitted light were complementary to those of reflected light, indicating that the iridescence is caused by the interference of light by the integumental multilayer structure. The present results are also consistent with the hypothesis that the iridescence has a role in increasing the contrast of males against the ambient light conditions in the daytime distributional depth of the species.

Two species of the genus Eudorella (Crustacea: Cumacea) were collected and examined from the Yellow Sea. A new species and one new record of Eudorella are described and illustrated. This new species Eudorella hwanghaensis sp. nov. closely resembles E. intermedia, but it differs from the latter species in bearing a distinct apical spine of endopod with uropod peduncle. The distribution of the new species is confined to the central portion of the Yellow Sea, and its distributional range coincides well with that of the Yellow Sea Bottom Cold Water Mass. Eudorella pacifica is recorded for the first time in Korean waters. It occurred in shallow waters and was distributed widely on both coastal sides of the Yellow Sea.

Siphonaria pectinata (Mollusca: Gastropoda) at Gibraltar foraged when exposed continuously or intermittently to air, when the relative humidity at the rock surface exceeded 75%. The paths followed by individual limpets were either single or compound loops beginning and ending at a home scar. In the main, outward and inward tracks were independent and there was little evidence of trail following. Siphonaria pectinata exhibited a range of crawling speeds but spent much of the excursion stationary or moving very slowly. Both duration of excursion and maximum foraging distance were very variable. No correlation between the size of S. pectinata and the duration of the excursion was apparent. The timing of activity may reflect an adaptive response designed to provide enough time to forage while avoiding predation, desiccation and dislodgement by waves.

The population structure of the European flying squid Todarodes sagittatus was studied using data of about 5000 squid caught in waters off the western Sahara between 1969 and 1997. The bulk of the population consisted of winter-spawned squid, which occurred as juveniles of 80–120 mm mantle length (ML) over the slope in spring, and as immature squid of 160–180 mm ML both on the shelf and slope in summer. In autumn, the squid attained 220–280 mm ML, matured, and shifted to the slope, where the spawning was supposed to occur in winter. Age and growth of T. sagittatus was studied using statolith ageing techniques. Assuming daily production of putative growth increments within statoliths, as well as sizes and proportions of immature and maturing females, the lifespan of the west Saharan populations of T. sagittatus lasts ∼1 y. Todarodes sagittatus is a fast growing squid at juvenile and immature ontogenetic phases. Early maturation (at ages 220–230 d in males and 250–260 d in females, respectively) and subsequent decrease of somatic growth rates caused rather small modal sizes of mature squid (250–300 mm ML) compared with those of their northern counterparts (350–420 mm ML). Both hatching dates and seasonality in occurrence of mature females shows that in waters off the western Sahara T. sagittatus spawns throughout the year with a well-pronounced winter peak.

Stomach contents of Todarodes sagittatus caught by trawlers working from 100 to 800 m depth in the Balearic Sea (western Mediterranean) were studied. From the 348 stomachs examined (153 males and 195 females) 33.62% were empty (39.21% in males and 29.74% in females). The diet of the squid was composed of 58 different prey items belonging to four major groups: Osteichthya, Crustacea, Cephalopoda and Chondrichthya. Osteichthyes, crustaceans and cephalopods were the most common prey, with a frequency of occurrence value of 84.85, 48.92 and 29.87% respectively. A change in the diet as the squid grows was observed, since juveniles feed basically on fishes while adults prey more actively on crustaceans. Analysis of the diet by size-classes reflected an ontogenetic migration to deeper waters since, parallel to the increase of size, a raise in the percentage of prey species inhabiting deeper waters was detected. Cannibalism was quite frequent, since T. sagittatus was the second most common cephalopod prey. Females had higher fullness-weight index and lower emptiness index than males, which reflects their major energetic demand for egg production.

When offered a choice between open water and a ‘vegetated’ area of an aquarium (artificial sea grass), mysid (Paramesopodopsis rufa) swarms always selected open water. In contrast, juvenile and adult sea horses, Hippocampus abdominalis, which feed by ambush predation, always selected vegetated areas even when their mysid prey occurred in the adjacent clear water. Lunging predators, Australian salmon (Arripis trutta), always preferred open water to vegetated regions of the tank. Increasing vegetation density, i.e. from low to medium habitat complexity had a positive effect on capture success of juvenile and adult sea horses feeding on mysid swarms. However, number of attacks by juvenile sea horses, but not adults, was significantly reduced in higher density vegetation. Number of attacks by Australian salmon decreased as vegetation density increased but capture success, nonetheless, increased. Density of vegetation did not significantly affect the number of unsuccessful attacks by adult sea horses. Whereas proportion of unsuccessful attacks increased with vegetation density for juvenile sea horses, it decreased for juvenile salmon. This result is thought to be due to the fact that high vegetation densities disrupt structure of the prey swarm, itself a defensive formation, leaving a large number of more vulnerable small groups. Cohesive escape responses of a large swarm are likely to be a more effective defence against a lunging predator than against an ambush predator whose strategy is to use stealth to avoid provoking escape responses. Dense vegetation will militate against this strategy.

Many coral reef fish are assumed to be conspicuous in their natural environment due to their bold and distinct colour patterns. However there have been few attempts to quantify the conspicuousness of coral reef fish under natural photic conditions. In this study, the effects of incident light and background conditions on the potential conspicuousness of four species of Hawaiian reef fish (Chaetodon auriga, Labroides phthirophagus, Thalassoma duperrey, Zebrasoma flavescens) were examined. The optical properties of water, coral and fish colour patterns were measured with an underwater spectroradiometer. Potential conspicuousness was quantified by calculating luminance (brightness) contrast and spectral (colour) contrast within fish colour patterns, and between patterns and natural backgrounds, i.e. water and coral. Under different illuminating and background conditions, the contrast from these fishes was highly variable. Different incident light conditions resulted in significant differences in inherent spectral contrast for L. phthirophagus. All fish had significantly different luminance contrast when the optical properties of the water backgrounds varied. Against coral backgrounds, T. duperrey and Z. flavescens had significantly different luminance contrast and L. phthirophagus and T. duperrey had significantly different spectral contrast. These results have important implications for theories on the adaptive significance of reef fish coloration since the conspicuousness of reef fish appears to be highly dependant on local photic conditions and therefore, some colour patterns may not be conspicuous in the wild as is often presumed.

Density and spatial distributions on an intermediate scale of two flatfishes—marbled flounder Pleuronectes yokohamae, and the brown sole Pleuronectes herzensteini (Pisces: Pleuronectiformes) within large (10,000–100,000 m2 patches of homogenous substratum (sand and silted sand)) were studied. Both species dominated in the demersal fish community. Densities of brown sole, were significantly higher in both types of habitat. Flatfish distribution was highly patchy and the mean fish densities in groups were as much as ten times higher than the mean fish densities in the area. More than 85% of all recorded flatfish were found within groups. Mixed groups with both species were most prevalent. The number of flatfish in one group ranged from 2 to 20. Brown sole was more abundant in the area and dominated in mixed groups. Levels of contacts between group members and densities within groups were inversely related to visibility condition. It is suggested that flatfish form a group and stay in the group, attracted by foraging movements of other flatfish and by plumes of upset particles caused by their bottom digging movements.

In this paper the macroscopic and microscopic morphology of the gonads of Helicolenus dactylopterus dactylopterus (Pisces: Teleostei) were analysed as well as its seasonal histological changes. The testicles are of the lobular type. The cystovarian ovaries have a central rachis from which the ovigerous lamellae are radially suspended. The gonoducts remain independent until they join together at the urogenital papilla which, in males, can be projected towards the exterior serving as a copulating organ. Sperm production is important from July to February. In contrast, the females only have mature and vitellogenic oocytes in winter, from December to February. In the west Mediterranean spawning takes place during the months of January and February. The ovaries contain clusters of spermatozoa for some ten months, from May onwards. By means of an optical microscope a specialized structure is detected, situated at the base of the interlamellar space, where male sexual cells are stored for a long period of time. Nevertheless, for several months many individual spermatozoa are also detected in the interlamellar areas, floating in the ovarian fluid secreted by the epithelium of the ovarian wall. It is still unknown whether the species under study is oviparous or viviparous, as until now, no intraovarian embryos have been detected in any of the specimens analysed.

Diet of common dolphins off the Portuguese coast was studied based on the examination of stomach contents of 50 stranded and incidentally caught animals. The relative importance of each prey species was assessed through occurrence, numerical and biomass indices. Common dolphins preyed on a large variety of items but four fish and two cephalopod species appeared to form the basis of their diet. Overall, sardine (Sardina pilchardus) was the most important prey, as given by all the indices used to measure prey relative importance. Although common dolphins preyed mostly on pelagic species, they seemed able to explore habitats with distinct features and employ various foraging strategies. A comparison between the diet of dolphins of different sex and size groups was not indicative of major differences. Common dolphins incidentally caught in fishing nets had taken a higher proportion of sardines, the target species of the fishery.

Six juvenile sperm whales were observed visually and acoustically in the confined waters of Scapa Flow, Orkney Islands during March 1993. General visual behaviours observed included slow travelling, head-outs, logging and side fluking but there were no observations of tail fluking within the confines of Scapa Flow. Recordings of the whales' vocalizations through hydrophones revealed a remarkably wide repertoire including clicks, rapid clicks, gunshots, chirrups, creaks, short trumpets, pips, squeals and clangs. Selected examples of these sounds were digitized and analysed as spectrograms. Clicks, rapid clicks, gunshots and clangs all showed a characteristic impulsive broadband signature. Chirrups, short trumpets and creaks were composed of rapid sequences of broadband impulses, although creaks were invariably faint and were difficult to illustrate well. Chirrups, short trumpets and clangs showed strong spectral peaks and pips were particularly unusual sounds with impulsive narrowband signatures composed of harmonically spaced peaks. Squeals exhibited prolonged, narrowband swept frequency signatures often with slight oscillation. All types of vocalization with the exception of clangs were heard from sperm whales during pure observation, minimum disturbance encounters in the field. Two attempts were made to remove the whales from Scapa Flow, the first being an enticement operation to lure the whales to open water with the use of underwater playback of sounds of socializing female sperm whales and the second a shepherding operation to drive the whales with a flotilla of vessels. The enticement operation was unsuccessful but the shepherding operation was successful, although the whales showed considerable reluctance to navigate a narrow channel to the open sea. During the shepherding operation there was a distinct change in the nature of the whales' vocalizations, with clangs predominating over other forms.

A variety of methods are available to extract chlorophyll from epilithic biofilms using solvents. The relative efficiency of these has not been determined simultaneously and there is no recognized standard procedure. In this paper techniques for sample collection, storage, preparation and extraction are reviewed and compared experimentally.

Extraction of chlorophyll was incomplete unless biofilms were fully hydrated. This factor was highly significant for all the solvents tested, with at least three times more pigment being extracted from hydrated samples than from dry ones. Methanol was the most efficient solvent, releasing over 96% of the total chlorophyll during a single extraction; hot ethanol extracted 86%, while acetone extracted less than 50%. Sonicating samples during extraction did not release any additional pigment. Centrifuging to remove suspended material did not alter estimates and was not advantageous. Rugose rock surfaces released more chlorophyll than smooth ones. However, a simple method to quantify surface rugosity at an appropriate scale was not available.

Based on these observations, a standard method for chlorophyll extractions from epilithic biofilms using 100% methanol at room temperature (20°C) is proposed. This technique requires considerably less supervision than previously preferred methods and gave a chlorophyll extract which was stable for 15 h.

A new species of marine yeast Kluyveromyces penaeid (Saccharomycetoideae) was isolated from the heart tissue of a subadult shrimp Penaeus chinensis during tissue culture. The yeast grew well in seawater supplemented with 2% shrimp extract, but did not grow in chemically defined media. The vegetative cells reproduced by multilateral budding and formed rudimentary pseudohyphae occasionally. Asci were spheroidal and evanescent containing 2–13 smooth or oval ascospores. The best temperature for the yeast to grow was 20–25°C and 37°C was lethal. The yeast grew well in half to full strength seawater supplemented with shrimp extract, but did not grow in 25% strength seawater. The carbohydrate fermentation test was positive, the diazonium blue B and urea hydrolysis tests were negative.

The polymerase chain reaction (PCR) was used to produce species-specific DNA markers (RAPDs) from two sibling cockle species and five other co-occurring intertidal bivalves. Amplification reactions with one single primer readily distinguished larvae and adults of Cerastoderma edule from larvae and adults of C. lamarcki, and from adults of Mya arenaria, Macoma balthica, Scrobicularia plana, Venerupis pulastra and Mytilus edulis. Random amplified polymorphic DNA (RAPD) is suggested as a simple and quick method to determine species identity in taxa that are difficult to identify on the basis of morphological characters alone, such as marine bivalve larvae.