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.

The radular activity of dogwhelks, Nucella lapillus, drilling mussels, Mytilus edulis, was monitored by piezoelectric transducers and recorded by an automatic digital system. In this way, for the first time, the drilling behaviour of dogwhelks was analysed in detail. Radular activity was similar to that previously recorded for limpets, each radular stroke (rasp) being formed by a sequence of 1–8 unit events, each probably corresponding to the application of one row of radular teeth on the substratum. During drilling, radular rasping followed a consistent pattern, each bout of radular rasping (lasting about 6–8 min) being followed by a period of radular inactivity (lasting about 35 min), when chemical dissolution is probably applied. The periodicity with which rasping was applied decreased during the drilling sequence (from about 25 min in the first quarter of the drilling process to about 40 min in the last quarter), together with a decrease in the rasping rate, i.e. number of radular rasps per min (from about 12 to about five rasps per min). Accordingly, the total number of radular rasps recorded during the first quarter of the drilling time was higher than during the other quarters (from about 3000 to about 500 rasps). The role of the radula in shell penetration was therefore rather extensive, accounting, during the first quarter of the process, for about 34% of drilling time. The results are discussed in relation to studies of chemical dissolution and mussel shell ultrastructure.

The reproductive biology of two aplacental viviparous deep sea sharks, Centroscymnus coelolepis and Centrophorus squamosus has been studied from 1735 and 675 specimens respectively, collected with bottom trawls between 600 and 1400 m depth off the west coast of the British Isles. A macroscopic maturity scale indicates that for both species, size at first maturity is greater in females than in males. In Centroscymnus coelolepis, genital maturity occurs at an average length of ∼86 cm for males and ∼102 cm for females. In Centrophorus squamosus, males are mature near 98 cm and females near 124 cm total length (TL). Smallest juveniles of both species are absent from catches: no specimens of Centroscymnus coelolepis shorter than 58 cm, nor specimens of Centrophorus squamosus shorter than 84 cm have been recorded. Ovarian fecundity is higher in Centroscymnus coelolepis than in Centrophorus squamosus. A maternal supply has been demonstrated for Centroscymnus coelolepis. Litter size has been estimated only in C. coelolepis because no pregnant females of Centrophorus squamosus were recovered. A dwarf embryo and a pair of twins have been observed. Segregation by sexual stage of development shows that immatures are generally found at greater depths than adults.

The spatial patterns of butterflyfish assemblages (Chaetodontidae) were examined within and between five islands of the Ryukyu Archipelago, southern Japan. Despite being the northernmost reef communities in the world and despite the severe natural and human-induced disturbances that have affected them since the 1970s, the coral reefs of the Ryukyu Islands have one of the most diversified assemblages of chaetodontids in the world. A total of 30 species were identified, and species richness per island ranged from 20 to 25 species. On each of the 45 stations prospected, between four and 17 species were recorded, and between 0.75 and 21.75 ind 250 m−2 were counted. Variation in species composition, species richness and abundance between islands was less pronounced than the variation within islands, where assemblages of the major reef environments (i.e. the reef flat, the reef edge, and the reef slope) were distinguished. The highest species richness and abundance were found on the reef slope and the reef edge. Canonical correspondence analysis revealed that depth, substrate complexity, and live coral cover influenced the distribution of chaetodontid fishes. These factors accounted for 20% of the variation in the species data matrix.

Octopuses (Eledone cirrhosa) feeding on crabs (Carcinus maenus) may penetrate the crab by a carapace borehole or puncture of the eye. In ad libitum feeding trials (632 crabs eaten), 31% of the predated crabs had a punctured eye, 57% had a borehole in the dorsal carapace. Eye puncture and boring occurred together in 6% of cases but 18% were neither punctured nor bored.

Feeding trials in which size of prey and size of octopus were controlled showed that the incidence of boreholes was greatest (>70%) in small crabs (<50 mm carapace width). Incidence of eye puncture (10% in small crabs) rose to 25% in crabs of over 50 mm carapace width and to over 40% in the largest crabs used (65–80 mm carapace width).

Large octopuses used eye puncture less frequently than small octopuses. Increasing the proportion of small crabs in the diet increased the subsequent incidence of carapace boring at all crab sizes. The results are discussed in relation to differences in prey handling efficiency at different prey sizes.

Populations of three species of juvenile Sparidae (Diplodus puntazzo, Diplodus sargus and Diplodus vulgaris) were sampled at different spatial scales in the north-western Mediterranean Sea over two years to follow growth after settlement. Length–frequency distributions were collected each week for periods of six months following the arrival of off-shore larvae in inshore habitats. Data were collected by underwater visual census along permanent transects.

Growth rate measured as the slope of the linear relationship between mean size and time varied between species. Diplodus puntazzo (0.160 mm d−1) and D. vulgaris (0.202 mm d−1), which are settling in winter experienced slower growth than D. sargus (0.567 mm d−1) which settles in summer. It is concluded that the difference was in part due to water temperature. Analysis of growth rate within each species also revealed significant differences among sites probably related to the currents and the water mass temperatures.

The feeding habits of John Dory (Zeus faber) were studied, based on the analysis of stomach contents from fish sampled in five groundfish surveys. These surveys were carried out off the Portuguese coast during different seasons between 1990 and 1992. The main aspects of feeding biology analysed in this paper are: ontogenetic diet changes, temporal variations in food composition and feeding intensity. Multivariate methods were used to investigate ontogenetic diet shifts. Two main length groups were identified: 8.0–24.9 cm fish, feeding mainly on dragonets and silvery pout, and 25.0–55.9 cm fish whose diet was mainly composed of blue whiting and snipefish. A transitional phase (24.0–30.9 cm fish) with a mixed food composition was observed. This ontogenetic diet shift does not seem to correspond to any important change in body morphology but it does coincide with the onset of sexual maturity in the species.

John Dory switched from a diet of small prey species with more pronounced benthic behaviour to a diet of larger schooling pelagic species. This suggests parallel evolution to more pelagic foraging behaviour. However, John Dory feeding habits appear to be largely controlled by the availability and accessibility of prey species: (i) the diet of adult John Dory is dominated by very abundant species; (ii) shifts in the main prey items between different times of the year and between different areas seem to be related both with their absolute and relative abundance in the environment and with the overlap between the depth distribution of predator and prey.

Continuous Plankton Recorder records from the North Sea and north-east Atlantic from September 1997 to March 1998 indicate an exceptional influx of oceanic indicator species into the North Sea. These inflow events, according to historical evidence, have only occurred sporadically during this century. This exceptional inflow and previous inflow events are discussed in relation to their similarity in terms of their physical and climatic conditions.

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.

One hundred and fifty intertidal fishes were captured at Jeffreys Bay in July 1996 and February 1997, and at De Hoop Nature Reserve in April 1997, South Africa. Caffrogobius caffer, Chorisochismus dentex, Clinus superciliosus, and Clinus cottoides were all parasitised by haematophagous larvae of the isopod, Gnathia africana, and between 22 and 81% of fishes were infested with 1 to 76 larvae each. Of those fishes examined for blood parasites, 35/46 (76.1%) had an intraerythrocytic haemogregarine identified as Haemogregarina (sensu lato) bigemina, but only Clinus superciliosus and Clinus cottoides were infected. Gamonts of the haemogregarine, some undergoing syzygy, were also present in 50% of stained batches of the anterior hindgut contents of G. africana larvae which had fed on Clinus superciliosus, but were absent from larvae taken from Clinus cottoides and Chorisochismus dentex. This study provides new host records for H. bigemina and further evidence that gnathiid isopods play a role in the transmission of the haemogregarine.

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.

Visceral fat content, liver weight and carcass weight changes in female sand smelt Atherina boyeri from three brackish lagoons of southern France were studied throughout the year 1993. Each of these three parameters showed a peak in autumn, the visceral fat content peak occurring earlier in the season. Moreover, when ovary weight was maximal, maturing and ripe fish exhibited a second liver weight peak in April, at the beginning of the reproductive season which extended from late February to late August. Reserves were stored in flesh, liver and the abdominal cavity after the end of reproduction and were utilized from late autumn to early summer to overwinter and reproduce. At the onset of the breeding season, visceral fat content and eviscerated weight in larger fish, which started reproducing earlier and stopped later than smaller ones, were relatively higher. From April onwards, as reproductive effort was at its highest, liver and ovary weights decreased. However, eviscerated weight in smaller fish and visceral fat content in larger ones rose slightly before they ceased breeding. It is suggested that the strategy, especially in younger fish, is to avoid complete exhaustion in reproduction. This reduces the risk of subsequent overwintering mortality and increases the chance of reproduction in the future.

The distribution and abundance of Ascophyllum nodosum, Fucus serratus and F. vesiculosus were described at four sheltered, rocky shores in the south of the Isle of Man. Canopy removal experiments were performed at mid tide level of one sheltered, canopy dominated shore to investigate the interactions between the dominant canopy alga, Ascophyllum nodosum and the competitively inferior canopy species of Fucus serratus and F. vesiculosus. Ascophyllum was removed from replicated plots, 2×2 m in size, in both winter and summer; the early growth and survival of fucoids in the presence and absence of the Ascophyllum canopy were monitored and the eventual development of a new canopy described. Juveniles of F. serratus originally present beneath the undisturbed canopy of Ascophyllum died following canopy removal but new recruitment resulted in some canopy development, principally in the winter experiment. Fucus vesiculosus, despite being completely excluded from the Ascophyllum zone of all four shores described, dominated the canopy removal plots of both winter and summer experiments. The Ascophyllum canopy did not recover over a five year period of observation, although a considerable increase in the abundance of Ascophyllum juveniles occurred.

Microstructural prominent discontinuities (checks) were observed within the statoliths of the short-finned squid Illex coindetii from the Strait of Sicily. Two hundred and forty-two pairs of statoliths were extracted from specimens (52–175 mm of mantle length, ML) sampled during autumn 1995 and analysed. Beside the check delimiting the postnuclear zone, up to four peripheral checks were detected in the peripheral zone. The occurrence of peripheral checks in the statoliths of immature squid was low (5–15%), whereas 80–95% of mature squid had peripheral checks. The mean number of peripheral checks within statoliths of mature males and females did not differ significantly (1.53–1.68 peripheral checks per squid). In mature and spawning females, the number of peripheral checks corresponded well with the number of spermatophoric bundles inside the mantles. Age at peripheral check formation was estimated for each sex, indicating that the first peripheral check formed at a significantly younger age in males than in females. Formation of the first peripheral check coincided with the start of maturation in both sexes, at a wide age range. The number of increments between peripheral checks subsequent to the first one declined sharply and remained similar in the two sexes, with a predominant mode between three and seven increments. A possible relationship between the number of peripheral checks and mating events in I. coindetii is discussed.

The current distribution and abundance of Elminius modestus (Crustacea: Cirripedia) were examined at 15 sites along the Portuguese coast in March/April 1998. Elminius modestus was found at two sites only but was absent from a site where it had previously been recorded. The site at Faro is the most southerly location on continental Europe where Elminius has yet been recorded and it is nearly 300 km south of where it was previously found.

Macrofaunal community structure was examined in a shallow sublittoral sea grass bed (Zostera marina L.) and adjacent unvegetated sediment in the River Yealm, Devon, south-west Britain, on a single sampling occasion in August 1995. The presence of Zostera had a significant influence on macrobenthic community structure in the River Yealm. Samples from inside the sea grass bed were characterized by significantly higher numbers of individuals and species, as well as by greater species richness and high faunal dominance (i.e. low evenness) compared with the unvegetated samples. High faunal dominance within the sea grass bed was attributable to the large numbers of a few species (e.g. the polychaetes juvenile capitellids, Spio filicornis, Exogone hebes, Nereis pelagica and the tanaidacean Apseudes talpa), while increased species richness was a result of a large number of additional rare (1–2 individuals) species. The greatest number of individuals was found in samples with the highest sea grass biomass. Multivariate ordination revealed a distinct separation of macrofauna communities from vegetated and unvegetated sites. Significance testing with ANOSIM shows that there were significant differences in community structure between vegetated and unvegetated habitats.

Attached cypris larvae and less than one month old metamorphs of Chthamalus stellatus and C. montagui (Crustacea: Cirripedia) were sampled from random quadrats on two shores in County Cork, Ireland, from July 1996 to June 1997. Cyprids of C. stellatus were much more abundant than those of C. montagui, but the relative abundance of metamorphs of the two species did not differ significantly. Cyprid abundance predicted metamorph recruitment intensity during peak settlement in C. stellatus but not in C. montagui.

Using acoustic telemetry techniques, the movements and habitat utilization of anadromous Arctic charr (Salvelinus alpinus) were determined when they entered the Freshwater Creek Estuary (Cambridge Bay, Northwest Territories, Canada) in the spring. The study was carried out during the transition from full ice cover to open water.

Between 23 June and 1 July 1996, nine adult Arctic charr were tagged with external acoustic transmitters. These fish were tracked until 6 July using two radio-linked acoustic array systems and a portable manual receiver with a directional hydrophone. Two transmitters measured temperature and location, one measured depth and location and the remaining six, location only.

All of the tagged charr remained in Cambridge Bay Estuary until the sea-ice had melted and the mouth of the bay was ice-free. Primarily, they remained in the warmer brackish surface layer which was ∼2 m thick and rarely moved into the colder underlying marine waters. As well, the tagged charr remained either near the shore or over offshore shoals, following the ice-edge as it melted down the estuary. Residence time in the estuary was greater than ten days for some fish. Therefore, in spite of evidence from controlled laboratory studies that have shown that Arctic charr are preadapted to the marine environment and are capable of migrating directly into seawater, this study shows that, in the wild, they prefer to remain in warmer brackish water until the sea-ice has melted and that the transition stage is longer than previously suggested.

The study of the digestive epithelium in Sagitta setosa, S. serratodentata, and S. pacifica revealed only a few morphological and cytological differences among the three species. The gut was divided in two main regions. The first is the cephalic region where the epithelium is composed of three distinct cell types (S1, S2, and S3), the ultrastructure of which is probably specialized either for the synthesis of mucosubstances (S1), or enzymes (S3), or both (S2). The second region of the gut extends to the trunk and is mainly composed of the intestine and a short vertical rectum. No intestinal diverticula were observed. The intestinal epithelium displayed two ciliated cell types, anteriorly, a secretory cell type (S4) containing large mucus-like granules, and a second cell type (A) predominated in the posterior part of the intestine. A-cells appear to have two main functions. Although they exhibit secretory granules, they also display typical endocytotic features in their upper half, i.e. coated vesicles, a well-developed tubulo–vesicular network and two distinct types of digestive vacuoles corresponding to an endosome–lysosome-like system. From the distribution and presumed function of the cells, the gut may be divided in two main functional units, i.e. the cephalic and trunk units.

Three macroalgae were studied: Enteromorpha sp. (Chlorophyceae), Hormosira banksii (Turner) Descaisne (Phaeophyceae), Corallina sp. (Rhodophyceae). Fractal dimensions (D) for the outlines of the three species were 1.24, 1.07 and 1.35 respectively in the step range 0.5–5.0 mm. All three species showed loss of epifauna on the falling tide; loss was greatest in Enteromorpha, least in Corallina. In Enteromorpha and Hormosira, most loss of epifauna was in the form of harpacticoid copepods; in Corallina loss was spread more evenly across the taxa. Epifaunal biomass and retention was much greater in Corallina than in the other two species, partially because of better water-retention properties. Enteromorpha and Hormosira both showed marked decreases in epifaunal diversity during emersion; Corallina did not.