Arcachon Bay was the last important shell culture area of the French Atlantic coast without a stock assessment of the accidentally introduced Crepidula fornicata (Gastropoda). Following a stratified sampling strategy, 205 stations were sampled with a dredge. The total biomass of C. fornicata was estimated at 155 tn (confidence limits: 72 tn) scattered on 2·4 km2, i.e. about 5% of the infralittoral area. This biomass is very low compared to other exploited shellfish sites. Amongst mean environmental parameters (such as bathymetry, temperature, salinity, sediment grain-size, anthropic activity), the major keyfactors differentiating Arcachon Bay from other French sites were searched to explain the differences in C. fornicata colonization pattern. It seems that the low biomass of C. fornicata, 30 y after its occurrence was first recorded in the bay, could be correlated to: (1) the scarcity of subtidal muddy sediments which are suitable for C. fornicata settlement; (2) the presence of large Zostera spp. beds on both intertidal and subtidal areas; and (3) the absence of bottom trawl fishing.  Growth, production and productivity (P/B) ratios were compared between five stations characterized by different hydrological and sediment parameters. Growth and productivity (0·3 y−1) were not affected by mean biomass suggesting a lack of population regulation by intraspecific competition.

Weight–length relationships of some of the most abundant bivalve species from the Algarve coast (southern Portugal) captured during several exploratory fishing surveys carried out during 2000 on a soft bottom in the subtidal zone down to 25 m depth are reported. For this study a total of 7429 individuals were sampled, belonging to 25 bivalve species in nine families. The most represented families were Mactridae and Veneridae with six species, immediately followed by the families Cardiidae (five species) and Donacidae (three species). The results revealed that most species presented isometric (11 species) or positive allometric relationships (11 species), while only a small minority of species displayed negative growth (three species).

Littoraria ardouiniana and Littoraria melanostoma are common snails in Hong Kong, living and feeding on mangrove trees. Gut content and stable isotopic analyses were conducted to investigate the littorinid's diets. Gut content analyses revealed these snails ingested bark, epidermal plant cells, fungi, and microalgae, but that broken plant cells were the most abundant food items in the stomach and faecal contents. The gut contents of the two littorinid species, either from the mangrove trees Kandelia candel or Aegiceras corniculatum, were similar and showed little temporal variation throughout the year. Dual stable isotopic analysis, which investigated the δ13C and δ15N values of the littorinids and their potential food items, indicated that these littorinids might feed on mixed diets composed of parts of the mangrove trees and other items available on the trees such as phylloplane fungi, microalgae and cyanobacteria. These epiphytic mangrove littorinids are generalist grazers which graze on the substratum non-selectively as they are constrained on their host trees, and their diets are, therefore, dependent on food availability on the trees themselves.

The effect of different salinities on the marine snails Hydrobia ulvae and Hydrobia ventrosa (Mollusca: Prosobranchia) was studied in laboratory experiments. For juvenile snails, neither shell growth nor the strength of interspecific competition were affected by salinity within the range of 15–30 psu. In contrast, we found that larvae of H. ulvae were sensitive to salinity: survival was higher and the larvae were more active in higher salinity. The negative influence of low salinity on H. ulvae larvae may not be the only explanation of the complementary field distribution of the two species, since habitat separation is present in areas without spatial salinity variation.

Two taxa of commercially exploited cuttlefish, Sepia officinalis and S. hierredda, are compared for the first time on the bases of quantitative morphology and allozyme polymorphisms. Morphometric measurements and meristic counts of selected soft and hard (cuttlebone) body characters, with allozyme electrophoretic analysis are used. Samples were obtained from north-west Iberian Peninsula and Senegalese waters (West Africa). Significant differences in mantle width, arm and hectocotylus length, numbers of rows of reduced suckers on the hectocotylus and in most cuttlebone measurements were found. Canonical discriminant functions of cuttlebone measurements for males and females were calculated. Allozyme electrophoresis for 33 presumptive loci showed low levels of genetic variability and 13 diagnostic loci between the two Sepia taxa. The genetic identities (I) in pairwise comparisons of populations of both taxa were I=0·582–0·596, which are typical values for congeneric species. These congruent morphological and genetic results strongly suggest that S. officinalis and S. hierredda are different species.

The trophic behaviour, stomach contents, and morphology of the feeding appendages, with emphasis on setae, of a species of Laomediidae, Axianassa australis (Crustacea: Decapoda: Thalassinidea), were investigated. This species is a deposit feeder. The 32 described setal types were clustered in four main categories: plumed, serrate, plumodenticulate and simple. By examining the setae and spatial position of the segments of the appendages, it is possible to infer that the main function of the 1st and 2nd pereiopods, the 3rd pair of maxillipeds, as well as the dactylus, propodus, carpus and merus of the 2nd maxilliped, is to brush particles. The ischium, basis and coxa of the 2nd maxilliped appear to be specialized for particle retention. For the remaining mouthparts, brushing is generally the main function of the basal endites, while the coxal endites retain particles. Patterns of morphological adaptations to feeding habits are proposed for the Thalassinidea based on a review of the literature. Setal diversity, ratio of plumodenticulate to serrate setal types and mandible morphology are linked to ecological adaptations to trophic modes. Conversely, the presence and degree of development of the crista dentata appear to be related to phylogenetic heritage rather than to feeding mechanisms. Stomach contents are also indicative of trophic modes used by the species; while the predominance of small particles can indicate either filter or deposit feeding, stomach contents with high quantities of large particles suggest deposit feeding as the exclusive trophic mechanism.

The present study checks on the validity of the hypothesis that heterozygosity and the fluctuating asymmetry (FA), common measure of the developmental stability, are linked in populations of wild and cultured stocks of Sparus aurata from five countries. Muscle and liver samples were analysed for variation in 26 allozymes and three microsatellite loci. Pectoral fin rays and upper and lower gill rakers of the first branchial arch were counted on the left and on the right sides of each fish. Fluctuating asymmetry existed in the majority of the samples although their values were consistently low, (0·305±0·147), but higher in the cultured samples. The allozyme heterozygosity values were always high, but lower in the cultured samples. The microsatellite DNA analysis produced similar results. Heterozygosity was higher in cultured individuals (except for the Greek samples). These findings seem to be early evidence that the reared samples are losing some genetic variation, especially due to the loss of the rarest alleles (which were present in the wild populations). Genetic drift, probably caused by propagation practices, is most likely responsible for the decrease of the genetic variation. No distinct pattern of geographic separation was identified.

The distribution of deep-water (150–4850 m) benthic and bentho–pelagic cephalopods in the north-east Atlantic is described, based on 592 specimens collected from commercial and research trawling. Thirty-six different species of cephalopod belonging to 14 families were identified, though problems remain with the taxonomy of some of the octopod genera. At the shallower depths (150–500 m) sepiolids were the most abundant group with five species identified. Sepiola atlantica, Sepietta oweniana and Rondeletiola minor were restricted to the shallow depths (<300 m), but Neorossia caroli (400–1535 m) and Rossia macrosoma (205–515 m) extended into deeper water. The squids Todaropsis eblanae and Loligo forbesi were also common in shallow areas (<250 m). Among the incirrate octopods, Eledone cirrhosa was found at depths of 208–490 m. Three putative species of Benthoctopus and two of Bathypolypus were identified occupying depths of 250–2700 m. Graneledoneverrucosa was caught at depths of 1785–2095 m. Cirrate octopods dominated the cephalopod catch from the deeper areas, with Opisthoteuthis massyae occurring from 877 to 1398 m, O. grimaldii from 2165 to 2287 m, Stauroteuthissyrtensis from 1425 to 3100 m, Cirroteuthismuelleri from 700 to 4854 m, Cirrothauma murrayi from 2430 to 4850 m and Grimpoteuthis (five putative species) from 1775 to 4877 m. Abundance estimates of the more frequently caught species were calculated from swept areas of trawls and sledges in the Porcupine Seabight and on the Porcupine Abyssal Plain.

Epixanthus dentatus (Crustacea: Brachyura: Eriphiidae) is a predator crab, commonly inhabiting East African mangroves, whose nocturnal and elusive behaviour usually prevents analysis of its natural diet and prey selection. The present study was carried out on a population inhabiting a peculiar mangrove habitat in which E. dentatus produces heaps of non-ingested parts of its prey. Fifty-nine of these accumulations of prey remains were examined and 17 species were identified as part of the diet of E. dentatus. Relative prey consumption was then analysed with respect to the relative abundance of prey species within the local faunal community. This methodology provided important information about prey selection by E. dentatus; in particular, gastropods were always strongly under-represented, while there was an active selection among the different crab species. Uca species were under-represented, while swimming crabs were also part of the E. dentatus diet, which shows that the latter is able to prey both at low and high tide.

The vent mussel Bathymodiolus puteoserpentis, a large vesicomyid clam and a smaller thyasirid were collected from an area of sediment subject to diffuse hydrothermal flow. The mussels live on the surface, the vesicomyids are partly buried and the thyasirids burrow in the sediment. The fine structure of the gills differs in the three bivalves. Bathymodiolus puteoserpentis hosts two types of bacterial symbiont, one methanotrophic, and another probably thiotrophic. The other two bivalves have single types of symbiont of different shapes. Stable isotope ratios of carbon and nitrogen indicate thiotrophy in the vesicomyid and thyasirid, but a predominance of methanotrophy in the mussel. This is the first time that such an assemblage has been found at a hydrothermal site on the Mid-Atlantic Ridge (MAR), with the different faunistic elements exploiting different energy resources.

A comparative study of some tagging methods for the great scallop (Pecten maximus) is reported and intended to increase reliability and reduce costs associated with tagging. Tags were tested for ease of application, legibility, visibility and retention prior to a 17-month study of Pecten maximus in suspended (pearl net) culture. Of the six adhesives tested (standard epoxy resin, rapid epoxy resin, underwater epoxy resin, dental cement, cyanoacrylate fluid and cyanoacrylate gel), rapid epoxy resin and both cyanoacrylates were successful, bonding strongly and quickly to scallop shells. Of the three tag types used, Shellfish Tags (Hallprint) were favoured because they were simpler to apply, more visible, easier to read, and held more data than both Micromarkers (Brady) and engraved codes. In long-term trials 550 scallops were double tagged with Shellfish Tags using cyanoacrylate gel. Loss rates were 16% for tags on the umbo and 0·4% for tags positioned in grooves near to the shell margin. Loss rates did not increase over the 17-month period.

The annual pattern of burial depth in natural populations of the infaunal bivalves Tagelus dombeii (Tellinacea) and Venus antiqua (Veneracea) is described in relation to annual food availability in both the water column and the sediment and abiotic factors (temperature and salinity) at Coihuín tidal flat, in southern Chile. A field experiment in which burial depth was measured in situ each month (over 14 months), with the aid of a fixed-length nylon thread attached to the shell. For T. dombeii the results showed a significant increase in burial depth with increasing bivalve size and syphon weight. Tagelus dombeii had a mean burial depth of 17·5 cm, which was three times more than in V. antiqua (5·30 cm). The burial depth dynamics for both species displayed a strong correlation with food availability in the water column. Approximately 60% of the variability in burial depth in T. dombeii and V. antiqua was explained by concentration of chlorophyll-a in the water column. Food concentration on the sediment surface did not effect burial depth, i.e. deposit feeding seems to be of minor significance in either species.

Cytological and biochemical changes in the digestive gland of Pecten maximus throughout a one-year period were investigated in the Bay of Brest (France) relative to lipid storage and glycogen and α-amylase concentrations in tubuloacinar terminations. Seasonal variations in both cell structure and biochemical composition were observed. These changes were independent of the tidal cycle, but correspond to phytoplankton abundance. From November to January, cells of digestive acini were hypertrophied due to the high lipid storage. From February to May, these reserves were markedly reduced, cell size decreased, and the acinar lumen was clearly apparent. From May to September, the RNAs transcribing for α-amylase increased, and a correlation was found between digestion events and lipid storage in acinar cells. The relationships between metabolite transfers from digestive gland to gonad and other tissues are described. Distinct lipid storage sites appear to be associated with maintenance energy and acute demand energy, such as gametogenesis when adductor muscle reserves have been depleted. The digestive gland may thus function as a relay organ during periods of energetic stress, notably during the first gametogenesis in February and March and for shell growth in early spring.

The distribution, abundance and recruitment of Chthamalus species were studied for one year at two rocky shores on the central coast of Portugal. Chthamalus montagui is the most abundant intertidal barnacle on the Portuguese mainland. Higher abundance of C. montagui was found on the lower levels of the more sheltered shore, which is closer to the influence of the Tagus estuary. Chthamalus stellatus was also present, in very low densities, and always confined to the lower level of the barnacle zone. Chthamalus stellatus was more common at the shore farther away from the estuary, in which exposure to wave action is higher. The metamorphs of C. stellatus settled at the studied shores are considered to be immigrants from other populations, where the density of adults is sufficient for cross-fertilization to occur. Chthamalus spp. recruited almost continuously throughout the year, with a peak between July and September and a gap during February and March. Variations in phytoplanktonic assemblages and temperature may be the main factors controlling the reproductive season of Chthamalus spp. Recruitment was usually stronger on the lower shore levels but extended for a longer period higher on the shore. Seasonalvariations of C. montagui abundance were greater on the lower levels of the more exposed shore. This is probably due to faster growth and higher mortality of barnacle populations occupying the lower shore levels at the more exposed habitats.

Feeding behaviour of the Japanese pygmy cuttlefish Idiosepius paradoxus, inhabiting sea grass beds, was observed in captivity. Pygmy cuttlefish preferred to feed on crustaceans and the feeding behaviour consisted of two phases, namely, attacking and eating. The sequence of attacking behaviour is divisible into three stages, namely attention, positioning and seizure. In the eating process, pygmy cuttlefish insert buccal mass into the exoskeleton of the captured crustacean. In this action the buccal mass elongates to a similar length to the first arm, and moves in various directions inside the exoskeleton and flesh is ingested as this behaviour proceeds. As a result, the empty exoskeleton remained intact when the pygmy cuttlefish finished feeding.

Population density, biomass, seasonal growth and gonad index of the heart urchin Echinocardium cordatum were monitored in muddy sediments of the Seto Inland Sea, Japan, from July 1998 to July 2000. Rates of sediment ingestion by the urchin were also measured. Juveniles settled in winter and their growth in the first year was rapid. Individual somatic mass in terms of ash-free dry weight (AFDW) increased from about 0·1 to 40 mg while the test length increased from about 2 to 20 mm. At the end of the second and third year (early December), somatic mass averaged 90 and 120 mg AFDW (test length=30 and 33 mm), respectively. The gonads of both year-classes matured during this period and spawning followed within two months. Individual E. cordatum (test length=29–34 mm) ingested sediments at rates of 14–43 mg wet weight per hour. Population density (28 m−2) and AFDW biomass (2·8 g m−2) of E. cordatum (test length [ges ]15 mm) were high at the start of monitoring (July 1998), remained relatively constant through the next spring and rapidly decreased to <2 m−2 and <0·2 g AFDW m−2, respectively, by December 1999. When abundant, E. cordatum comprised about 60% of the macrobenthic biomass in the study area and its annual production in AFDW reached about 1·5 g m−2 y−1, suggesting substantial contributions of the urchin in material cycling through the sediments.

Diets of the four main flatfish species, Arnoglossus laterna,Bothus podas (Bothidae), Buglossidium luteum and Solea solea (Soleidae), inhabiting shallow sandy bottoms near the Gulf of Fos (north-west Mediterranean) were analysed to elucidate food partitioning between their juveniles (1+ group) in nursery areas. The two Soleidae were principally active during the night, and the two Bothidae during the day. The four species all mainly fed on the three most abundant categories of prey in the area (polychaetes, molluscs and crustaceans) but showed different food preferences. Arnoglossus laterna and B. luteum mainly preyed on crustaceans and molluscs (gastropods and bivalves) whereas Bothus podas and S. solea preyed principally on polychaetes and bivalve molluscs. Food niche width was clearly higher in A. laterna and Buglossidiumluteum (13·3 and 14·2 respectively) than in Bothus podas and S. solea (3·2 and 3·6 respectively). Overall food niche overlaps (T) obtained for each pair of fish ranged from 0·33 to 0·58. Overlap was higher between species of the same family but did not reach a significant level. Food niche overlap differed according to the period of the day but did not show any important seasonal variation. Differences in feeding rhythms, food preferences and body sizes, reduced the direct food competition between the juveniles of the four flatfish species, allowing their coexistence within the same nursery zone, despite close periods of settlement.

Specimens of the chemoautotrophic symbiont-bearing hydrothermal vent clam Calyptogena pacifica were collected from hydrothermal vents at the Endeavour segment of the Juan de Fuca Ridge. Total lipid was extracted from gill, foot and mantle tissues, and lipid class and fatty acid composition determined by thin layer chromatography with flame ionization detection (TLC–FID), gas chromatography (GC) and gas chromatography with mass spectrometry (GC–MS). An abundance of n–7 monounsaturated fatty acids (MUFA), especially in the gill, reflected the large contribution of chemoautotrophic symbiotic bacteria to the nutrition of this clam. The absence of n–8 MUFA suggests that C. pacifica does not contain methanotrophic symbiotic bacteria. Low levels of highly unsaturated fatty acids (HUFA) such as 20:5 n–3 and 22:6 n–3 were detected in C. pacifica and their presence is attributed to a source other than chemoautotrophic symbiotic bacteria. Significant levels of non-methylene interrupted dienoic fatty acids and eicosatrienoic acid (20:3) were also detected in C. pacifica and it is suggested that these fatty acids are synthesized from n–7 MUFA as alternatives to HUFA. In contrast to shallow water bivalves, elevated levels of triglyceride were detected in the gills compared to the mantle.

Large numbers of small individuals (pediveligers and juveniles <5 mm) are routinely recorded in size–frequency distributions of mussel samples collected from deep-sea chemosynthetic environments. If recruitment of invertebrates to deep-sea hydrothermal vent sites were via long-distance dispersal, as is typically assumed, one would expect recruitment ‘events’ recorded in size–frequency distributions to be difficult to detect, due to loss of larvae in an open system over large distances. If one imposes mesoscale oceanographic phenomena that minimize dilution of larvae (such as eddies shed from hydrothermal vent plumes) and episodic spawning, expression of this mesoscale corralling at the level of population structure would likely be limited to discrete records of recruitment events encountered serendipitously during haphazard sampling in space and time. The ubiquity of large numbers of post-larvae in mussel samples from a number of disparate sites is likely not serendipitous, but instead may reflect the importance of local sources and sinks of propagules in maintenance of mussel populations.

Todarodes sagittatus (N=1131) were opportunistically sampled from commercial and research trawling in Irish and Scottish waters between 1993 and 1998. The results suggest that the species is common in deep waters (>200 m) to the west of Ireland and Scotland, particularly in late summer and autumn. The size of squid caught was related to depth, with larger squid caught deeper, and is indicative of an ontogenetic, bathymetric migration. Females were more common (sex ratio 1·00:0·46), and attained a larger maximum size (520 mm mantle length (ML)) than males (426 mm ML). Mature females (360–520 mm ML) were caught in deep water (>500 m), between March and November, with a large catch of mature females taken off the west coast of Ireland in August 1996. Mature males (300–426 mm) were found from August to November. Potential fecundity was estimated to range from 205,000–523,500 eggs female−1. Putative daily increments in statoliths indicated a life cycle of slightly over a year, with rapid growth of approximately 1·8 mm d−1 during subadult and adult life. Fish were the most important prey of T. sagittatus and 17 fish prey taxa were identified, of which pelagic species were the most important.