Thirteen carefully prepared drogued buoy assemblies have been deployed in the eastern subtropical North Atlantic giving ~20 buoy years of Lagrangian data at a depth of 200 m. The buoy results together with hydrography have revealed the structure of the eastward flowing Azores Current (AC). The main jet had a transport of 26 Sv (near 28°W) with compensating counterflows in March 1992. Jet and counterflows were readily seen in the ADCP current structure and evident in the upper layer temperature (salinity) structure on an isopycnal surface. Buoys and hydrography showed that the adjacent westward flowing counterflows resulted in recirculation both north (anticlockwise circulation) and south (clockwise circulation) of the AC - the Subtropical Recirculations. South-south-west flow (3 cm s−1) occurred in the central region of study west of the Canary Islands. The long-term movement measured in the south or northern North Equatorial Current region was 3·5 cm s−1 west-south-west. The mean south displacement per year of the buoys was 2·2° of latitude to the south and most of this displacement occurred in the first half of the year (February-August). The maximum westward displacement rate occurred six months later in October and November. The Subtropical Front/Azores Current region was identified as a zone of increased levels of kinetic energy (>100 cm2s−2) at a latitude near 34°N at the 200 m level, stretching for >2000 km, and as a marked horizontal winter sea surface temperature contrast at a latitude near 36°N. Winter mixing created an outcropping region of water with density in the range 26–4<σ0<26·6 kg m−3 along the Subtropical Front near 34°N with a maximum vertical extent of 200 m.

The evidence for variations in winter phosphate concentration as a component of the ‘Russell Cycle’ has been re-examined. The change from high phosphate concentrations prior to 1930 is the largest apparent variation in concentration through the period 1923–1987. However, these values are the result of a retrospective application in 1938, of a salt correction factor of 1–35. The justification for this factor is examined. It is concluded that there is sufficient uncertainty in the accuracy of the pre-1948 measurements of phosphate concentration to preclude their use in long time-series analysis. A statistical analysis of the post-1948 data shows that a simple first order autoregression model provides a perfectly adequate description of the data; the data can be considered as essentially random, with a small component of carry over from one year to the next. The evidence is weak that variations in winter concentrations of phosphate support the Russell Cycle hypothesis.

In September 1993 the Irish Sea floor near the Sellafield nuclear reprocessing plant was surveyed by towed video to assess the distribution, abundance and behaviour of large burrowing invertebrates believed to be important in the transport and mixing of radionuclide-contaminated sediments. Sixteen stations were surveyed, covering a range of sediment types. Burrow openings and mounds were counted and assigned to species where possible. Particular attention was paid to the similarities and differences between the features observed and those produced by the same species in Scottish sea lochs, the source of most relevant ecological data. Several different burrowing communities were identified from bottom topography. Offshore muddy sands supported dense populations of the thalassinidean crustacean Callianassa subterranea, in burrows similar to those described from the North Sea. Coarse sediments closer inshore had C. subterranea at lower density, with the thalassinidean Upogebia deltaura and the crab Goneplax rhomboides also present. Softer muds were dominated topographically by ejecta mounds of the echiuran Maxmuelleria lankesteri and burrows of the Norway lobster Nephrops norvegicus. The thalassinideans C. subterranea, Jaxea nocturna and Calocaris macandreae were also present at low density. Surface bioturbation features in this habitat were very similar to those described from sea lochs. Population densities estimated from surface bioturbation features were always lower than counts of specimens from box-cores. The visual survey therefore gave minimum estimates of population density. Available data on rates of bioturbation by the species concerned are collated to give rough estimates of biogenic sediment transport in the habitats surveyed.

The taxonomy of six species and one subspecies of Natatolana, which have previously been recorded from the north Atlantic Ocean and Mediterranean Sea, is reviewed. Natatolana caeca, N. gallica, N. gracilis and N. neglecta are redescribed from the type material. The location of possible type material of N. borealis is reported and a redescription of this species is provided, based on material from the type locality. Natatolana neglecta var. imicola is recognized as a valid species. Natatolana schtnidti is regarded as a junior synonym of N. imicola based on comparison of type material and this material is used to redescribe the species. Distribution records for these species are summarized from examination of material held in various collections and a key to separate these species is provided.

The 1989 discovery of a large dorsal eye on the hydrothermal vent shrimp, Rimicaris exoculata, debunked the prevailing opinion that all animals living around deep hydrothermal vents were blind. Recent dives with DSV ‘Alvin’ recovered new bresiliid shrimp [Chorocaris (Lucky Strike) and Chorocaris (Broken Spur)] from two new vent fields on the Mid-Atlantic Ridge. The Lucky Strike species has recently been named Chorocaris fortunata and may be the same as the Broken Spur species - the retinal morphologies reported here are very similar. Like R. exoculata, C. fortunata has a visual apparatus adapted to the very dim light of its environment. Although in both species enlarged, non-imaging eyes appear to have evolved from the stalked compound eyes typical of caridean shrimp, those of C. fortunata are forward-facing whilst that of R. exoculata is located dorsally. The massive array of photosensitive membrane (rhabdom) of C. fortunata lies beneath a smooth cornea within a matt, white, reflecting matrix and occupies 80% of the available volume of the photoreceptors compared to the expected 10–15% of shallow water decapods. All screening pigment is located out of the light path at the bottom of the retina. There is no ultrastructural evidence for cyclic rhabdom shedding or renewal. Thus the cellular organization of C. fortunata is remarkably similar to that of R. exoculata and distinct from its surface-dwelling relatives. This suggests that in these species imaging optics have been sacrificed to achieve the increased visual sensitivity necessary to detect the very dim light emitted from the throats of the black smoker chimneys around which they live

One Scottish and two Aegean samples of Nephrops norvegicus (Crustacea: Decapoda) were allozymically tested using a total of 110 individuals and compared with two already characterized Adriatic populations. Three main characteristics of their genetic structure emerge: a highly homogeneous allele pattern, a strong heterozygote deficiency at some loci and a significant genotypic variance among populations, mainly caused by the Pgm locus. Population subdivision, intraunit inbreeding, bottlenecks and selective constraints are taken into account to allow for these genetic features, although none of them proved decisive. The search for straightforward characters differentiating Norway lobsters of geographically different areas proved unsuccessful, although a significant genotypic differentiation was noticed among our samples. Observed D values among the geographically distant samples indicate a very low genetic divergence, so that no clear phyletic conclusions can be traced on the sole allozyme-gene analysis.

This study tested the hypothesis that predator odours alter behavioural responses of hermit crabs to other chemical stimuli. Stimuli that cause alarm and shell-related behaviour (hermit crab haemolymph and two gastropod flesh extracts), and stimuli that did not cause shell-related behaviour (sea-water and predator haemolymph) were used. Individual hermit crab responses to stimuli were observed in ambient sea-water and predator odour. In the absence of predator odour, hermit crab haemolymph and gastropod flesh extracts stimulated shell grasping behaviour. Locomotion was the major response to sea-water and stone crab haemolymph. Crabs behaved consistently when repeatedly exposed to a particular stimulus. In general, addition of predator odour to mixtures, resulted in decreased shell grasping and increased locomotion. Shell fit was a poor predictor of behaviour for the size range of crabs tested. Hermit crabs respond to, and discriminate, a variety of complex odour mixtures.

Field observations and laboratory experiments were made on Cyclope neritea, a small (~10 mm diameter) burrowing stenoglossan gastropod with a flattened shell found in very high densities (>200 m2) in Paleohori Bay on the south coast of Milos (Aegean Sea). Cyclope neritea forms a high proportion of the biomass at seeps in this bay, where the medium to fine sand overlies hot, sulphidic brines. About half the animals were found on the surface in the daytime, an exception to the normal habit of this species which usually emerges from the sediment only at night. The C. neritea were aggregated on the thinner bacterial mats over the seeps. In the laboratory, C. neritea remained active for 3 h at sulphide concentrations up to 1 mM, the highest concentration in the interstitial water in the upper 25 mm of sediment at the seeps. Although the species can tolerate elevated salinity and temperature, it shows little adaptation for sulphide detoxification by oxidative pathways. It may survive at the seeps by its behaviour pattern, especially the use of the extensible siphon to access oxic water above the sediment boundary layer, and perhaps by exclusion of sulphide from the tissues. Cyclope neritea ingests large quantities of sand together with adhering bacteria and diatoms, but also scavenges on other animals killed by the extreme conditions of the seeps.

The Nassarius reticulatus complex (Mollusca: Gastropoda) is a common and morphologically variable organism of the Lusitanian marine province. The taxonomic status of the different morphs has been the subject of considerable debate for over a century. About 50 individuals of each N. nitidus and N. reticulatus morphs were collected in November 1994 from the same area (Ria de Vigo, north-west Iberian Peninsula). Preliminary screening by allozyme electrophoresis for 27 enzymes resolved 24 presumptive enzyme loci. There were no deviations from the Hardy-Weinberg expected proportions at most polymporphic loci for any morph. Five and two enzyme loci were completely and partially diagnostic loci, respectively, between the morphs. The genetic identity of morphs (1=0.658 ±0.095) was characteristic of congeneric species. The absence of electrophoretically recognizable hybrids in sympatric populations provides clear evidence that the two morphs are reproductively isolated within the study area. These genetic results corroborate other reported biochemical, morphological and behavioural differences between the morphs. Consequently, these data strongly suggest that the taxa N. nitidus and N. reticulatus must be considered as separate species.

The study of growth rates in the prosobranch snails Hydrobia ulvae and H. ventrosa under field conditions showed that growth rate of snails infected by different trematode species is species-specific. Trematodes from the families Microphallidae and Heterophyidae cause gigantic growth whereas species from families Notocotylidae and Bunocotylidae have no effect on growth rate. This discrepancy is attributed to the different pathogenicity of the parasites. However, under experimental conditions with different host population densities the effect of infection by Bunocotyle progenetica effect varies from a tendency to stunt the growth (under high density) to a significant increase in growth rate (under low density). The effect of Himasthla sp. (Echinostomatidae) was shown to be population-specific. These findings agree with a previously reported hypothesis that the growth response of trematode-infected snails depends (among other things) on supplement of host-parasite system with food. Trematode infection caused parasitic castration in all studied host-parasite combinations. It is argued that the phenomenon of gigantism in infected snails is a consequence of the reduced sexual ability of the host. The correlation between snail growth rate and penis size of infected males was negative. The correlation between growth rate and penis size was not found in uninfected snails from the same age group

Long-term variations in shell growth of the mollusc Arctica islandica (Mollusca, Bivalvia) from the northern North Sea have been assessed retrospectively using the annually deposited internal growth lines. Relatively young specimens yielded a detailed year-to-year chronology while the growth record of specimens older than 30 y yielded a time series with a length exceeding 100 years. The long-term growth trends demonstrated a marked alternating sequence of periods in which growth was below and above expectation. A 33-y long cycle could be discerned. Since the 1960s the growth patterns in Arctica from two nearby locations were opposite, while they resembled each other in the period before 1960.

Seasonal variation of clearance, absorption and respiration rates of mussels Mytilus edulis (Mollusca: Bivalvia) and cockles Cerastoderma edule (Mollusca: Bivalvia) of various size classes have been measured under ambient temperature and sea-water conditions. Food availability was kept almost constant during the measurements.

Allometric body weight coefficients were bcl=0.5 for clearance and about br=0.7 for respiration rate of both species. Stepwise multiple regression suggested no relation for clearance rate of mussels with temperature and reproductive condition throughout the year. Respiration rates of mussels were highest during the reproductive period. Excretion rate was measured for mussels only and showed an allometric coefficient of bex=0.7 and an increase with temperature in spring. For cockles a significant relation of clearance rate, body weight and temperature was observed; at low temperature, clearance rates of small animals were more reduced than for larger animals. Respiration rates of cockles showed a significant relationship with temperature and reproductive condition.

Ontogenetic changes in the body morphology, morphometrics, age, growth, maturation, fecundity, feeding spectrum and parasites were studied in 218 specimens of the oceanic nektonic squid Onychoteuthis banksi and in two specimens of the rare planktonic squid Chaunoteuthis mollis (Onychoteuthidae) caught in the tropical waters between 1977 and 1990. Similarities between the two species in major taxonomic features and in several morphometrical indices suggest that C. mollis is in fact a mature female of O. banksi with degenerated mantle and fin muscles and lost tentacles. Thus, C. mollis will be considered as a lesser synonym of O. banksi. Statolith microstructure analysis reveals that O. banksi is a slow-growing squid with low maturation rates, spending the first 240–260 d of life in the epipelagic zone. The main features of the reproductive strategy include earlier maturation of the males, small eggs (0.2–0.5 mm in diameter by the end of protoplasmic growth), synchronous development of oocytes and high potential fecundity (51,000–205,000 eggs). Onychoteuthis banksi is an opportunistic predator, shifting to a fish and squid diet much earlier and at smaller sizes (20–40 mm ML) than ommastrephid squid. The feeding activity of small and medium O. banksi (20–80 mm ML) is a little higher and that of large O. banksi (80–148 mm ML) is lower than in ommastrephids of the same size. The helminth fauna of O. banksi is impoverished and consists of ‘food parasites’: larval Didymozoidea and Scolex spp. The level of infection is low, only reaching -52 specimens per host in large squid. The nature of the life cycle of O. banksi and possible evolutionary trends in the development of the ‘Chaunoteuthis’ stage for maturation and spawning of females in the deep water are discussed.

Behaviour during homing movements and downstream migration of yellow- and silver-phase American eels (Anguilla rostrata) was observed using continuous ultrasonic telemetry in a tidal estuary. Homing subadult (yellow-phase) eels, non-displaced yellow-phase eels and adult (silver-phase) eels all used tidal currents as a transport mechanism (‘selective tidal stream transport’) and possibly as a means of orienting and moving in an appropriate direction. Yellow-phase eels displaced up the estuary and migrating silver-phase eels moved mostly at night and during ebbing tides. Yellow-phase eels displaced down the estuary moved mainly during flooding tides both day and night. Non-displaced eels used selective tidal stream transport to make long, round trip excursions and to move about their home range. Eels were at or near the surface during most of their movements, but were also vertically active, diving transiently to mid-water or to the bottom. During movements, the eels tended to drift with the current, or to swim slowly in the direction of the current. Although they used the tidal currents effectively as a transport mechanism, they were not precise in timing their movements to maximize transport on each tide. This study demonstrates that both yellow- and silver-phase eels use selective tidal stream transport during movements in tidal habitats and excludes some cues previously proposed to regulate the behaviour.

Underwater behavioural observations were conducted to evaluate the relative importance of cleaning behaviour in three species of common north-eastern Atlantic wrasse (Teleostei: Labridae). At the study site, the only cleaner was Centrolabrus exoletus. A total of 12 species was cleaned, with the wrasse, Symphodus melops and Labrus bergylta being the species most frequently cleaned. Neither S. melops nor Ctenolabrus rupestris, known to be cleaners in other sites or in captivity, could be observed cleaning other fishes. Centrolabrus exoletus was found to be a facultative cleaner fish with cleaning acts representing only 7% of the observed feeding acts. In focal observations of host fishes, the incidence of cleaning acts reached a level (11 h-1 per host) similar to that reported for tropical reef fishes and probably reflects the high numbers of cleaners available. Some factors that may affect the origin of the cleaning interactions are discussed.

The dominant planktonic calanoid copepods in inshore and estuarine habitats in northern European waters; the Acartiidae, Centropagidae and Temoridae, produce eggs which survive and can remain dormant in the sediments (Marcus, 1996). Eggs of Eurytemora survived passage through the guts of fish larvae, in contrast with eggs of Pseudocalanus (Conway et al., 1994). Eggs of Paracalanus do not survive in sediments (Marcus, 1991). Lindley (1992) suggested that families within the superfamily Centropagoidea, including Eurytemora but not Paracalanus and Pseudocalanus, produce eggs which remain viable in sediments. Previous work on these eggs has been from subtidal sediments, although Naess (1996) showed that calanoid eggs survived in sediments in seasonally drained fish ponds.

This study constitutes a first approach of the use of a stereological method for estimating potential fecundity in cephalopods. Squid samples were taken in two regions from the south coast of Portugal. In Olhäo, commercial trawlers provided mainly immature squid during winter. In Quarteira, a summertime traditional jigg fishery provided maturing and mature squid, which were used in the fecundity estimates. A total of 38 female squid, Loligo vulgaris (Cephalopoda: Loliginidae), from all maturity stages were analysed. The results revealed that: (1) the development of the ovaries is monocyclic and the oocyte growth and development is asynchronous; (2) oogenesis proceeds in six histological stages, showing statistically different oocyte maximum diameters; and (3) the best estimate of potential fecundity seems to be obtained by counting all oocytes in the ovaries of the mature females in maturity stage IV

Thirteen species of Amphipoda have been recorded from the stomachs of plaice and 11 species from dabs, with Perioculodes longimanus the most notable prey oedicerotid in both flatfish species sampled from the shallow sublittoral zone (<-6 m depth) at Kames Bay, Millport. Plaice took mostly bivalve siphon tips (Angulus sp.). Polychaetes were more numerous in larger plaice. Sand gobies specialized on small crustaceans, taking 13 amphipod species inter alia (with P. longimanus again the most notable oedicerotid). Amphipod numbers in sand goby stomachs increased with the length of the fish. Neither dabs nor sand gobies consumed bivalve siphon tips and only rarely consumed polychaetes. Although amphipods formed only a minor part of the diet of plaice, at the population density known for this species in this bay, its depredations would still constitute an important selective agency governing patterns of activity in epibenthic oedicerotids.

Eight individuals of Mullus surmuletus (Teleostei: Mullidae) ≤80 mm total length were captured in shallow water in the Firth of Lorn, western Scotland in August and September 1995. The species is rare on the west coast of Scotland and the occurrence of juveniles is a new record for the area.

The red mullet (Mullus surmuletus L.) is a species whose distribution is centred on the Mediterranean where it forms the basis of a commercial fishery (e.g. Renoñes et al., 1995). Outside the Mediterranean it is found on eastern Atlantic coasts from the Canaries northwards to the English Channel and the southern North Sea where it is ‘moderately common’ (Wheeler, 1969). Further north it is regarded as rare (Wheeler, 1969; Hureau, 1986) and the northern limit is variously given as Scotland (Lythgoe & Lythgoe, 1992) or southern Norway (Wheeler, 1978). Most northern records are from the North Sea (Rae & Wilson, 1954; Rae & Lamont, 1964), presumably reflecting the intensive fishing effort in this area. Records to the west of the British Isles are few and have been summarized by Gordon (1981) and subsequently by Henderson (1986, personal communication), including one from the Faeroes (Blacker, 1977). All recorded occurrences in western Scotland are of adult fish (26–31 cm) caught by commercial fishing vessels and juveniles have never been reported from this area. This note documents (Table 1) the capture of small individuals (N=8) in shallow water off the west coast of Scotland in an area where they had never been recorded previously, despite intensive studies of the local fish fauna since 1970 (R.N.G., personal observation; Gibson, 1973; Gibson et al., 1993). The eight fish were caught on Tralee beach, Ardmucknish Bay, Firth of Lorn, Argyll (56°31′N 5°29′W). The sea bed in this area consists of fine sand (Gibson et al., 1993). It is possible that their occurrence is linked with the unusually warm summer of 1995 allowing juveniles to penetrate further north than usual. Water temperatures at 2–5 m on 29 August, 1995 were 14.3°C compared with a maximum of 13.6°C recorded over the period 1986–1989 (Gibson et al., 1993).

A pilot study was conducted to follow condition and swimming performances over two months using three samples of 50 juveniles of white sea bream, Diplodus vulgaris. The initial result indicated that the weight-length relationship followed the model; W=5.2xl0-3L349. According to this relationship, condition indices were estimated for each individual as the observed weight related to the computed weight. Measures of swimming velocities realized in an artificial flume show variations through time with an increase and decrease directly correlated to condition indices. Maximum speed of an individual was measured at 12.3 cm s1. Analysis of environmental conditions indicated that the decrease of condition index and swimming performances was related to bad weather which induced turbid water in juvenile habitats.