The abundance of the common intertidal barnacles, Chthamalus montagui, Chthamalus stellatus, Semibalanus balanoides and Elminius modestus has been monitored since 1951 at a site near Cellar Beach, River Yealm, south Devon. Counts are made at 12 levels on a transect between high tide and low tide. The two chthamalids are of warm-water distribution while S. balanoides is a boreo-arctic species; changes in the abundance of these species are linked to environmental temperature. Maximum fluctuations occur in the lowermost third of the intertidal zone. The proportion of Chthamalus adults is correlated with annual mean inshore sea temperature two years earlier, while the proportion of S. balanoides adults is negatively so correlated. This relationship accounts for over 40% of the variance. A smaller part of the variance (<20%) is explained by intensity of larval settlement, also related to climate. The fourth barnacle, E. modestus, is an Australasian immigrant that arrived in England during World War II and reached south Devon in 1948. It increased during the 1950s on the transect but has since stabilized at a low level of abundance that shows large interannual variations not directly related to temperature. Between 1951 and 1975, coinciding with a secular decline in sea temperature, there was a long-term trend towards reduction of Chthamalus and increase in S. balanoides; this trend has reversed since. Removal of the long-term trend reveals a short-term fluctuation of approximately 10-y frequency that correlates with a cycle in sea temperature two years earlier. These cycles are close to the 10–11 y solar (sunspot) cycle between 1951 and 1975.

The free-running locomotor activity rhythms of freshly-captured swimming crabs Liocarcinus holsatus and L. depurator have been studied in constant conditions in the laboratory. L. holsatus captured in the intertidal zone of sandy beaches showed strong circatidal activity rhythms with maximum activity at high tide. L. holsatus captured in the sublittoral zone had a clear tendency to show circadian activity rhythms with highest activity during day-time hours. L. depurator occurred only sublittorally and showed circadian activity patterns with highest activity during the night. Exposure to hydrostatic pressure cycles of tidal amplitude and periodicity, entrained strong circatidal activity rhythms in previously arhythmic L. holsatus. This activity pattern also showed a marked circadian component. Exposure to the same regime entrained a circadian rhythm, but not a circatidal rhythm in L. depurator. In the sublittoral zone L. depurator is active mainly during the night, whereas L. holsatus, is active mainly during the day. This may constitute a behavioural mechanism for minimizing competitive interactions between these two sympatric crabs.

Clones of Ditylum brightwellii and Thalassiosira nordenskioldii were isolated from New York coastal waters, and PCB-resistance in D. brightwellii was induced in the laboratory by exposure to increasing concentrations of PCB. Resistance could not be similarly induced in T. nordenskioldii, but was serendipitously discovered in unexposed cultures that had undergone sexual reproduction.

Cells of the resistant strain were substantially larger than those of the sensitive strain in both species. Larger vacuole space seemed to account for this in D. brightwellii, but in T. nordenskioldii larger cells contained more carbon. Experiments with14C-PCB tracer indicated that PCB accumulation was less in resistant strains of both species. Neutral lipid content per cell, as determined using the fluorophore Nile Red, was similar for resistant and sensitive strains of both species. Sub-cellular examination of lipid droplets in D. brightwellii suggested that the PCB-resistant strain may be sequestering this lipophilic toxicant in a location removed from physiological activity. In T. nordenskioldii a decreased ratio of neutral lipidxarbon may reduce intracellular accumulation of PCB. These diatom species have developed PCB resistance in the highly PCB-polluted Hudson River estuary and, since they are the preferred food of dominant copepods, they may offer less PCB per unit ration to zooplankton grazers.

The hypothesis that the level of chromatic polymorphism in intertidal isopods is related to their distribution and seasonal fluctuations in abundance was examined in northern Spain. Four species were used, Dynamene bidentata, Dynamene magnitorata, Cymodoce truncata and Cymodoce emarginata. Only for Dynamene species were results consistent with initial hypothesis. The most common colour morph in Dynamene bidentata was uniformis which is the most flexible phenotype, allowing effective concealment in most of the environments where the species occurs. Dynamene bidentata is the most abundant species of isopod in northern Spain, where it is abundant along the shore and throughout the year. Distribution of D. magnitorata, Cymodoce truncata and C. emarginata is restricted to macroalgal assemblages at low tidal levels. Seasonality is also important in D. magnitorata and C. truncata. The number of colour morphs and phenotypic diversity was larger in D. magnitorata than in D. bidentata. Only one colour morph was found in C. truncata and four in C. emarginata.

The characters widely used for identifying members of the Ampelisca diadema group of species (A. diadema, A. spinipes, A. tenuicornis and A. armoricana) are reassessed. Highly variable characters are discarded in favour of more stable ones. Both sexes of all four species known from the north-east Atlantic are figured and diagnoses and a key to the species are provided.

In order to investigate the characteristic species and the relative importance of selected environmental conditions of rocky bottom communities in coastal waters and to estimate their richness, 27 sites in the Brest area were surveyed by diving. The abundances of underwater species, from a check-list of 115, were plotted as number of individuals or colonies in m2 or in percentage cover of the rock, against the environmental conditions (depth, bedrock slope, substrate type and sediment nature of the nearest soft bottom). Raw data were converted to biovolume expressed as mm3 m–2 and expressed as log 10 (x + 1).

Various correspondence analyses were applied to these data: the first included bedrock slope (lit/dark surfaces) and takes into account the four biological formations according to the depth. It shows zonation with depth and decreasing light as factor 1, hydrodynamic conditions (waves or current) as factor 2, mixing of estuarine and oceanic waters as factor 3 and turbidity as factor 4. Four species assemblages emerge from these four axes, for which the main species contributing to the four axes may be considered as characteristic species. These correspond well to four broad communities described in British waters: very exposed to wave-action, semi-exposed to wave-action, exposed to strong tidal current, very sheltered sites. The second analysis, in which lit and dark surfaces are distinguished, but some very close sites are fused together, shows in detail the photophilous or sciaphilous nature of the species. Values of hydrodynamic conditions and percentage of surface light plotted on the 'stations-points' of the graphs allow drawing of a factorial network which may be used as hydrodynamic and illumination scales.

The behaviour of two intertidal chitons (Mollusca: Polyplacophora) from the western Indian Ocean (Acanthopleura gemmata and A. brevispinosa) and one from the Caribbean Sea (A. granulata) were analyzed in order to assess the spatial and temporal organization of their foraging activity. Individual paths were recorded in the field using a motographic method based on LED-tracking and the speed variation during each excursion used to reveal the places where the animals slowed down or stopped for the purpose of grazing. Foraging segments of each trajectory were selected according to a threshold speed which was individually calibrated. The three species of Acanthopleura exhibited graded foraging strategies of different spatial complexity. Acanthopleura gemmata focused its foraging on a few large feeding sites well separated from its permanent home. Acanthopleura brevispinosa exploited more subdivided feeding grounds not distinctly separated from its rest area. Acanthopleura granulata spreads its grazing activity over many small segments, throughout each excursion. Due to different tidal and diel constraints on their activity the three species allocated different absolute time to foraging, but the fraction of time spent foraging relative to the total excursion was similar in each.

Based on qualitative data on prosobranch gastropods present at eight seamounts and islands of the Vitória-Trindade Seamount Chain off the eastern coast of Brazil, similarities at the species level are examined, and the effects of selection for different modes of development varying with increasing distance from the coast are investigated. Number of species decreases significantly from the continent towards easternmost localities. Similarity coefficients and cluster analysis suggest that similarities are greater among the western seamounts, followed by the eastern, most oceanic localities. Subtidal stations on Trindade Island show less similarity at specific level when compared with the remaining sublittoral stations. Percentages and absolute numbers of species with intracapsular metamorphosis decrease rapidly away from the coast in the sublittoral localities. However, there is little variation for the ratio planktotrophs/lecithotrophs among these localities, and their percentages remained constant over the entire Chain. In spite of the slightly wider range of distribution of planktotrophs within the Chain, the observations suggest that both planktotrophs and lecithotrophs can be effectively dispersed, probably by passive larval transport, in an ‘island-hopping’ pattern across the relatively small distances (100–250 km) that separate summits in the Chain. Notwithstanding shallow, subtidal conditions and intense isolation, percentages of planktotrophs and lecithotrophs also do not vary at the subtidal Trindade stations.

To evaluate the relative importance of tentacular crown and body surface in sabellid respiration, experiments were carried out on Eudistylia vancouveri (Kinberg, 1867), a long narrow worm living in a permanent tube in the intertidal zone. This species irrigates its tube by peristaltic waves, as do most species of Sabellinae and this allows water circulation inside the tube for body surface respiration.

Measurements of oxygen uptake after amputation of the tentacular crown indicated a reduction of about 80% of the total respiration. This value was higher than that found for other Sabellinae studied. Some predictions about other species were made on the basis of the present observations and of comparison with species having similar aptitudes.

The habit of living in a narrow tube protruding from the sea bottom, as occurs among sabellids, implies some adaptations concerning feeding, excretion and respiration. In the order Sabellida, the prostomium is reduced and fused to the peristomium which usually forms a large tentacular crown (Fauchald, 1977) with both feeding and respiratory functions. Its relative importance in respiration, however, is still little known. Survival after crown amputation suggests that this structure is not essential for respiration; moreover some species can autotomize and regenerate it (Berrill, 1931; Okada, 1934). In sabellids, respiration can in fact occur at the level of the body surface and this is made possible by the flux of the water contained in the tube which is generated by the worm itself: i.e. irrigation. Sabellinae species can actively irrigate their tubes by waves of muscular contraction of the body wall in either direction.

Activity of Patella vulgata was monitored in the asymmetrical tidal regime of an Irish sealough, Lough Hyne, and also outside the lough in a normal tidal regime. An automated method was used, allowing continuous records to be made over two weeks. Most activity occurred at night while the limpets were emersed. Rainfall depressed activity. There was little activity during daytime emersion, contrary to the results of previous studies in which low-shore limpets foraged diurnally as well as nocturnally. Timing of activity in relation to tidal coverage was similar inside the lough and outside.

Activity of high-shore limpets within the lough was greater at spring tides than at neaps, but that of low-shore limpets was greater at neaps. Outside the lough, both high-shore and low-shore limpets showed greater activity at spring tides. Reasons for the differences are discussed.

Using Maximum Entropy Spectral Analysis, three periodicities underlying limpet activity were indicated. These were at h, 124 h and 8–2 h. When limpet activity was simulated by adding three sine waves of appropriate periodicity, rhythms very similar to those recorded from the shore were produced.

An intensive investigation of the benthic biology of the Porcupine Seabight, to the south-west of Ireland, was carried out by biologists from the Institute of Oceanographic Sciences Deacon Laboratory (IOSDL) between 1977 and 1986. More than 400 benthic samples were obtained during the study using towed gears and corersover the depth range 200 to 4500 m. Transect and time-lapse photography was used extensively. This paper summarises the techniques employed and provides an analysis of the depth and seasonal coverage. In addition a review is provided of available data on the physical, chemical and geological characteristics of the Porcupine Seabight area, including information collected during the IOSDL study. Finally, existing publications based on the study are listed.

The discrete habitat requirements of Ophelia bicornis from the Exe estuary are reported in relation to: the influence of tidal activity; the nature of the sandy substratum; the associated meiofauna; the interstitial bacteria; the interstitial water, organic matter and calcareous material; and the interstitial and sand-adsorbed free amino acids. The interrelationships of these features as potential limiting factors in the highly specific littoral distribution of O. bicornis is speculated upon.

Gelidium pristoides dominates the lower and mid-eulittoral zones of rocky shores in the eastern Cape, South Africa. A disproportionately high percentage of the plants is attached to barnacle and limpet shells, or restricted to rock crevices. Our experiments at Port Alfred indicate that this distribution is caused by grazing by the limpet Patella oculus and/or strength of attachment of the plants to the different substrata. Exclusion of limpets caused an approximately four-fold increase in the cover of G. pristoides on rock, and an increase from almost 0 to 80% cover on sterilised (dead) limpet shells. Measurements showed G. pristoides to be more than 50% more strongly attached to barnacle and limpet shells than to rock. The distribution of G. pristoides on the various substrata is largely determined by limpet grazing and possibly the different strengths of attachment to the different substrata. The upper distribution limit of G. pristoides is set by physical effects of emersion and was largely unaffected by limpet exclusion. Competition with other algae is important in setting the lower limit: in the sublittoral fringe, although limpet exclusion enhanced recruitment, juveniles were later displaced by articulated corallines, and adult transplants senesced because of encrusting coralline epiphytes.

A study was made ofGeryon trispinosus (Herbst) from the Porcupine Seabight in the north-east Atlantic, based on detailed examination of 687 specimens, and carapace length data for a further 2000. Evidence indicates that males become sexually mature at 30–35 mm carapace length, and females between 12 and 15 mm. There is probably a terminal anecdysis, in males at 55–65 mm and in females at 45–50 mm. The chelae show limited heterochely and marked right-handedness in both sexes. Relative growth in chelae and abdomen followed expected patterns, except that the right chelae of males decreased in relative size at the puberty moult. Seasonal reproduction is indicated: laying in September/October, hatching the following May, and settlement from the plankton in August/September.

The influence of temperature on the duration of the embryonic and larval development in Necora puber (L., 1767) was studied. Nine different temperatures were used for the eggs and seven for the larvae, in both cases ranging from 2 to 35°C. The temperature range where visible development was obtained was between 4 and 31°C, with the lowest lethal temperature (temperature at which the eggs did not show any sign of development and development did not resume when the eggs were placed at 15°C) being between 2 and 4°C and the highest lethal temperature between 31 and 35°C for both eggs and larvae.

Temperature was found to be inversely related to developmental time. The incubation period (D) fluctuated between 76 days at 10°C and 17·6 days at 25°C, with an increase in the rate of development (100/D) from 1·13 to 5·55 between these two temperatures. The larval period varied between 48·5 days at 15°C and 28 days at 25°C with rates of development of 2·08 and 3·57 respectively. The adjustment equations used show that temperature has a greater accelerating effect on eggs than on larvae. A simple potential equation, D=aT, describes the relationship between temperature and developmental time better than the Belehrádek equation, D=a(T-t).

Acording to the fitted equations developmental time from spawning to the first postlarval stage is completed in 91–105 days at temperatures of 13–15°C which is very close to our experimental data. The model proposed also fits most of the data from the available literature even those for other species such as Liocarcinus holsatus (Fabricius, 1798) and Carcinus maenas (L., 1758), which suggests that a similar response of developmental time vs temperature could be expected from other related Portunidae.

Thyasira gouldi, an arctic bivalve mollusc of the family Thyasiridae, has symbiotic, probably chemoautotrophic, bacteria living in its gills. In specimens collected from Loch Etive in Scotland in 1989, after the local population had undergone an unexplained decline, the gill bacteria contained numerous virus-like particles 60 nm in diameter. The bacteria are not lysed by the virus, and the particles are not present outside the bacteria except in phagocytic vacuoles of the gill cells where the bacteria have been digested, leaving the virus particles unchanged. Similar particles have been discovered in bacterial symbionts of Thyasira flexuosa, but in much smaller numbers.

A massive toxic bloom ofChrysochromulina polylepis occurred along the Swedish west coast in May and June 1988 with severe effects on most biota in shallow marine habitats. In the present study, the effects on the common dog-whelk,Nucella lapillus was investigated in the archipelago at the mouth of the Gullmar Fjord.

Mortality varied throughout the archipelago, with extinction of populations in the inner parts and survivors found only on the outermost islands. Even on these sites, mortality could be as high as 98­99%. Extensive samples of survivors and dead animals were divided into five age groups dependent on size and wear of the shell. The cohort consisting of 3­4 year old individuals suffered the lowest mortality, while mortality was almost total in younger and older cohorts. In each age group, except the oldest, survivors were significantly larger than the dead.

The number of egg capsules laid per female in 1988 seemed normal, but about half of the capsules were empty. The number of young per capsule was significantly lower in 1988 compared to 1989, but the young were significantly bigger.

The demersal ichthyofauna of the continental slope of the Porcupine Seabight, eastern North Atlantic, was studied from 144 samples taken by three different types of otter trawl. At least 118 species from 43 families were represented among some 54,000 specimens collected from 247 to 2172m soundings. Collectively, the catches were dominated in species richness by the Macrouridae, Alepocephalidae and Squalidae and in abundance by the Synaphobranchidae, Macrouridae and Moridae. Separately, relative abundance of species was more similar between the two larger trawls, setting their catches apart from the smaller net. Gear selectivity evidently accounted for this variation, which was examined by an index we developed and call species fidelity. This accounts for patterns of continuous faunal change with increased soundings concomitant with variance in species adult size and mobility. In pursuance of a more accurate representation of relative biomass and abun-dance than achieved hitherto, the best estimate, within the limitations imposed by the sampling gears and regime, was derived from a combination of the mean values per 200m stratum of the two large trawls with the addition of those of the eel, Synaphobranchus kaupi, from the small gear. Tentative comparisons between these results and those from elsewhere suggest that the Porcupine Seabight is generally lower in biomass and similar or lower in abundance. It was concluded that an accurate indication of ichthyofaunal structure with increased soundings can only be achieved through a detailed knowledge of the size structure of each species over its entire sounding range synthesized from a multi-trawl investigation via analyses of species fidelity.

The presence of Stoloteuthis leucoptera in the Mediterranean is recorded on the basis of three specimens, including an adult male, caught by IKMT and by commercial otter-trawl in the Ligurian Sea. The hypothesis of a recent immigration is discussed.

The list of Mediterranean cephalopods (Mangold Wirz, 1963; Torchio, 1968; Bello, 1986; Mangold & Boletzsky, 1987) includes the Sepiolidae of the subfamily Heteroteuthinae, whose members are supposed to be pelagic throughout their life cycle. Mangold Wirz (1963) recognizes in the Mediterranean fauna the unique species Heteroteuthis dispar, the other authors include H. atlantis Voss, which Voss himself (1955) reported at Messina. To this group may now be added Stoloteuthis leucoptera (Verrill, 1878) a species until now recorded in limited Atlantic areas. Verrill (1881) wrote “This species is an exceedingly beautiful one, when living, owing to the elegance and brilliancy of its colours and the gracefulness of its movements. In swimming it moves its fins in a manner analogous to the motion of the wings of a butterfly.”

Back-calculated egg fertilization (spawned) dates and growth rates for young-of-the-year bass, Dicentrarchus labrax (L), captured from Loughor Estuary, Oxwich Bay and Ogmore Estuary, south Wales, UK, during 1988 and 1989 were compared. Spawned date frequency distributions indicated that the bass spawning season began in late February and continued until early June in 1988 and early July in 1989.

There were no significant differences in the frequency distributions of back-calculated spawned dates for the bass populations, between either sites or years, which suggested that any variations in growth rates were attributable to characteristics of their respective environments. Growth rates were determined for bass cohorts resulting from early, midor late-season spawnings at Oxwich and Loughor in 1988 and Oxwich, Loughor and Ogmore in 1989. There were only slight intra-annual differences between the mean growth rates of bass cohorts at the same site, suggesting that bass from early cohorts would be larger at any given time of year. In 1989, growth was considerably faster at Oxwich and Loughor than at Ogmore, where food supply was considered limiting. However, between-site variations in growth rate were small in comparison with inter-annual differences. The faster growth rates observed at Loughor and Oxwich in 1989 were attributed to higher water temperatures.

Relationships between growth rate and subsequent survival of young-of-the-year bass, and the relative importance of estuaries as nursery habitats for juvenile bass, are discussed.