In a preliminary study of the marine benthos of Ría de Ares-Betanzos, 50 stations covering the quadrant delineated by the coordinates 43°26′42″N–43°20′42″N and 08°18′54″W–08°10′12″W were sampled and sediment samples analysed for particle-size composition, sand, silt and clay content, degree of sorting, median diameter and grain-size diversity of sediments. Organic and inorganic content, total carbon and nitrogen, carbonates, organic carbon/total nitrogen ratio and bathymetric data were also collected. On a smaller scale a few stations were sampled for sediment redox potential and pH measurement. The salinity, temperature and oxygen content of the overlying water was also assessed.

Cluster analysis and Principal Component Analysis methods were used to describe seabed heterogeneity and the pattern of sediment distribution within the ría, and to relate the environmental variables to each sediment type. Sediments were predominantly fine to very fine sands, and exhibited a direct depth-related gradient, i.e. with the finer grades, higher organic carbon and silt and clay occurring at the shallower areas of Pontedeume, Ares and Redes inlets and Ría de Betanzos sector where terrigenous input was important. Carbonate, organic carbon and organic matter maxima occurred in the central sector of the ría where most mollusc recruitment takes place: revealing the chiefly bioclastic origin of sediments. Taking into account the geological and hydrographic processes, explanations for the formation of the sedimentary bottoms in Ría de Ares-Betanzos are provided.

The putative impact of subsistence foragers along the Transkei coast of South Africa was determined by comparing the community-level attributes of infratidal macrofaunal assemblages in three ‘no-take’ reserves with those at adjacent exploited localities. The objective of this study was to ascertain whether the differences in the assemblages found at exploited and non-exploited localities were consistent along this coast. Two-way ANOVAs indicated that the presence/absence of exploitation had no effect on univariate community measures. Macrofaunal biomass was the only measure which showed significant differences amongst locations and interaction effects. Abundance/biomass comparison curves revealed that all the exploited sites except one showed the configuration typical of moderately disturbed sites and that all the non-exploited sites except one showed the trend typical of undisturbed sites. Two-way crossed ANOSIM tests indicated that treatment and location both had significant effects on these assemblages and that there were also significant differences between each pair of locations. The latter probably reflects regional differences in species composition due to the fact that this coast lies at the junction of two zoogeographic marine provinces. The multidimensional scaling (MDS) ordinations derived from abundance and biomass estimates revealed two major clusters of sites, one representing sites in the southern region and the other sites within the central and northern regions. The non-exploited sites within each region were situated above and to the right of the corresponding exploited sites. Similarity percentage analyses (SIMPER) indicated that the major species contributing to the average dissimilarity between the exploited and non-exploited localities varied regionally. There was, however, a fair amount of consistency in terms of the functional groups highlighted by these analyses. Some of the species adversely affected by exploitation are dependent on primary substrata either for their food supplies or for attachment. Likewise many of the species which appeared to benefit from exploitation were phytal-associated forms.

Divisional morphogenesis of the marine hypotrichous ciliate, Tachysoma ovata was investigated based on protargol impregnated specimens. Its morphogenesis reveals the following peculiarities: (1) there is a definite period during which the anterior part of the newly formed adoral zone of membranelles (AZM) in the opisthe connects with the parental AZM which remains unchanged during the morphogenesis. (2) The anlagen of left and right marginal rows do not develop simultaneously. (3) The replication processes of macronuclear segments are not recognizable during cell division. It is likely that the replication takes place during the interphase. (4) The origin of the fronto-ventral-transverse (FVT) cirral anlagen in the opisthe is characteristic: in other Tachysoma spp. these primordia are generated either from differentiated parental ciliatures (or are orientated by pre-existent organelles), or by division of the proter's FVT-cirral primordia. (5) The primordium of the undulating membranes in the proter always keeps the form of two streaks (so-called ‘semi-anlagen’). There is no conspicuous dedifferentiation or reorganization of the undulating membranes. A morphogenetic comparison with other species of this genus was carried out.

A morphological, cytological and genetic comparison of putative conspecific populations of Spirastrella sp. cf. mollis (Porifera: Demospongiae) from both sides of the Isthmus of Panama revealed a very high level of genetic differentiation together with morphological and cytological differences. The main differences were the distribution of the spirasters within the choanosome, the size and shape of spirasters 1, and the size and shape of inclusions within type I cells. Consequently these two populations clearly belong to different biological species. The Atlantic one, S. hartmani sp. nov. corresponds to what previous authors have called S. cunctatrix in the Caribbean. The finding of this new species raises to three the number of Spirastrella spp. known from the Caribbean Sea. The Pacific species is named here S. sabogae sp. nov. The levels of gene divergence found between S. hartmani and S. sabogae (Nei's genetic distance D=2.30) were as high as those found between different genera in other groups of invertebrates. Similarly exceptionally high values of gene divergence have been found between other congeneric sponge species and may be indicative either of a higher rate of molecular evolution or a very slow rate of morphological evolution in the Porifera compared to other metazoans.

A new species of the genus Celleporella (Celleporella galaica sp. nov.) is described from material collected in Galicia (north-west Spain).

Temporal patterns in metazoan parasite community diversity of Crassostrea gigas, (Lamellibranchia: Ostreidae) were studied in the Exe Estuary at monthly intervals over one year and in relation to host age-classes. A total of four metazoan species was found to parasitize C. gigas in the Exe Estuary: the turbellarian Paravortex sp., cercaria Lepocreadiidae, metacercariae of Renicola roscovita and the copepod Mytilicola intestinalis. Only R. roscovita and M. intestinalis were present in all months throughout the year and in all host age-classes. Analysis of the metazoan parasite community at individual host level revealed little variation in community structure with respect to season or host age, as only a slight increase in diversity values was observed during the summer months. However, community diversity does vary from year to year, as shown by comparison between host age group samples in three consecutive years. None of the parasites are specialist to oysters but all appear to be widespread and abundant parasite of other lamellibranch species.

The role of the ommastrephid squids Illex coindetii and Todaropsis eblanae (Mollusca: Cephalopoda) collected from two areas in the north-eastern Atlantic waters (north-west Spain) as hosts for larval ascaridoid nematodes was examined from November 1992 to November 1993. The morphology, morphometric growth, population dynamics and electrophoretic identification of the anisakid nematodes was described. The correspondence of Anisakis type I larvae recovered from both squid species within the sibling species Anisakis simplex B is confirmed by comparative data on morphology, morphometry, and genetic evidences. Almost all somatic structures showed progressive and continuous allometric growth corresponding with increase in worm length. Seasonal changes in parasite population levels were evident in both sampling areas.

In situ grazing activity of mesoplanktonic copepods was investigated by the fluorometric method during an algal spring bloom in a zone of oyster farming in Marennes-Oléron Bay. The grazing activity of copepods was overall higher during the night than during the day for three species (Temora longicornis, Paracalanus parvus and Acartia clausi), but peaks also appeared during the day for all of them. Individual ingestion rates and daily rations were higher during neap tide (low suspended particulate matter (SPM) concentrations) than during spring tide (high SPM concentrations). During ebb tide (when SPM concentrations were the lowest) the feeding activity of T. longicornis, P. parvus and A. clausi was significantly negatively correlated with algal concentration. Our work suggests that during the algal spring bloom in the farming area of Marennes-Oléron Bay the pressure exerted by mesoplanktonic copepods on the algal stock was very low, as a consequence of: (i) high algal concentrations in the field (resuspension and high phytoplanktonic production); (ii) low ingestion rates when high algal concentrations were observed. The likely ingestion of non-fluorescent particles by copepods is discussed.

Supralittoral splashpools representing 312,000 m2 of shoreline in Barkley Sound, British Columbia, were surveyed seasonally for tidal elevation, size, water properties, macroflora and faunal constituents coincident with colonization by Tigriopus californicus (Arthropoda: Copepoda). Overall, 90.1% of pools containing T. californicus were found between 3.0 and 5.0 m above lowest normal tide, with an average surface area-to-volume ratio of 7.06. Copepod populations were found at water temperatures of 6–33°C; salinity of <1–139 psu; pH of 6.1–9.5; and of 1.1–13.7 mg l−1 oxygen. Sediment and vegetation was sparse in T. californicus pools (mean cover 15.79±10.6% in 9.4±11.1% of pools, all species), and consisted most commonly of Enteromorpha compressa and Scytosiphon lomentaria and its Ralfsia-like alternate phase. Common fauna included mites, amphipods, littorines, and nematodes, with the highest diversity of co-inhabitants occurring in spring. Factors such as wind, wave action, and incidental fauna are discussed as potential agents of dispersal for splashpool copepods.

Two recently-distinguished species of Chthamalus (Cirripedia) are found on rocky shores in the north-eastern Atlantic: C. stellatus predominant on islands and headlands and C. montagui more abundant in bays. Larvae of the two species were produced in laboratory cultures to describe and compare the morphology and to allow identification in plankton samples. Nauplius larvae of C. stellatus are up to 30% larger than those of C. montagui. Differences in setation are minor. The two species are easily distinguishable from the size and shape of the cephalic shield. Chthamalus stellatus has a subcircular shield with longer body processes in later stages while C. montagui is more ovoid. The former develop more slowly in culture than the latter. Chthamalus stellatus larvae in a culture at 19 °C reached stage VI in 16 d compared to 11 d for larvae of C. montagui at the same temperature. The morphology and longer development time of C. stellatus larvae suggests adaptation to a more oceanic lifestyle and wider dispersal to reach more fragmented habitats than larvae of C. montagui.

In the summer of 1995 a massive kill of the dog-whelk, Nucella lapillus, occurred in Bude Bay on the north Cornish coast. High mortality was detectable along 12 km of shoreline. The only other intertidal species affected appeared to be another neogastropod, Ocenebra erinacea. The cause of the kill is unknown but the evidence suggests that it occurred in early July following an extended period of warm, calm weather in June. Possible causes of this event are discussed: algal toxicity may have been responsible since an algal bloom was detected offshore in July in the area. Laboratory experiments exposing gastropods to different species and concentrations of microalgae, designed to test whether N. lapillus is more sensitive than Monodonta lineata and Littorina littorea, gave inconclusive results. No comparable kill has occurred in the Bude area for at least 20 y, but it is suggested that nutrients from a newly-constructed, offshore sewage outfall may now stimulate local algal bloom development during calm weather periods.

Loligo vulgaris (Cephalopoda: Loliginidae) is a commercially important species in the cephalopod trawl fishery in the Saharan Bank (21–26°N). This study on squid in central-east Atlantic waters aims to examine some important aspects of its reproductive biology. In the period from May 1993 to April 1994 monthly samples of L. vulgaris were collected from this commercial trawl fishery. The maturation pattern for males and females was described from the proportion of immature, maturing and mature animals in the samples and using a maturation index. A range of reproductive indices derived from the morphometrics of the somatic and reproductive systems were also estimated to provide comparative information. The proportion and an abundance index of mature and immature animals in commercial landings in the period 1983–1994 were calculated to provide comparative results of maturity and recruitment respectively. Peaks of mature animals were mainly seen between November and January. The summer months exhibited the maximum recruit abundance. Age determinations were also undertaken in order to obtain the hatching peaks and to complete the proposed life cycle of L. vulgaris on the Saharan Bank. A main hatching peak was observed in spring, particularly in May. The age–size relationship suggests differences related to sex and possibly to hatching season. The wide range of size at maturity observed in male L. vulgaris is analysed and discussed. Males showed a seasonal pattern in size at maturity. The dorsal mantle length–body weight relationship and the sex ratio were determined. The sex ratio exhibits a seasonal pattern in relation to body size. Results are compared with information on this species from European waters.

The data presented here demonstrate that the sea cucumber Cucumaria frondosa secretes a biologically active mucus that helps maintain gametogenic synchrony among conspecifics. Either a whole mature individual or a sample of its freshly collected mucus was able to initiate gametogenesis in conspecifics that were in the gametogenic recovery stage when other environmental conditions, including daylength, were maintained constant. Similar results were obtained when the mucus was kept in seawater for less than 3 h prior to its use, whereas after 6 h in seawater, the mucus had lost its inducing properties. Laboratory experiments showed that the mucus was produced in lesser amount during late summer and autumn; the production rapidly increased in early January to reach a peak a few months before the June spawning, in 1992 and 1993. The increment of mucus production was concurrent with the initiation of gametogenesis. Synthesis of mucus was maximal in individuals having attained gametogenic maturity and minimum in individuals with less developed gonads. At first relatively stable in seawater, the mucus gradually lost its integrity within a period of 3–5 h, suggesting that the mucus may be carried over long distances by currents, thus allowing a transfer of information before its complete degradation. This phenomenon was observed in the field where streams of mucus could be followed by SCUBA divers as far as 20–30 m away from the secreting animal. The data presented here are the first evidence of the important role played by mucus secretion during the gametogenic processes of an echinoderm.

Changes in the reproductive strategy of Sphaerechinus granularis (Echinodermata: Echinoidea) according to food availability were examined by comparing gonadal index changes from two populations with different food conditions. The better nutritional situation was confirmed by a repletion index always higher without significant inverse relationships with the gonadal index. The two populations exhibited a different reproductive strategy during their life cycle. The food limited population showed a delay in reproductive competence, a lower gonadal index and an increase in relative gonadal growth with age. This population showed a seasonal inverse relationship between the consumption index and the gonadal index during the spawning period. A discussion based on the variations in the main life history parameters between the two populations: reproduction, somatic growth, longevity, underlines the plasticity of this species which must maximize its reproductive output in terms of changes in food availability. The adaptive value of this plasticity was observed by the reduction in somatic growth which decreases the energetic cost of maintenance and by the increase in size of the feeding structure (Aristotle's lantern) which improves food acquisition.

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.

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.

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 stomach contents of 344 four-spotted megrim, (Lepidorhombus boscii) and 159 megrim (Lepidorhombus whiffiagonis), off the eastern coast of the Gulf of Valencia (Spain), were analysed. The two species examined do not appear to have very similar diets, based on the species composition of prey. The vacuity coefficient is not high for any of the species, the main food being Crustacea (Decapoda and Mysidacea). Also Amphipoda and Teleostei are components of the diet. Variations in the food of both fish related to their length show few small crustaceans as prey of the major specimens. Finally, there was evidence for seasonal variation of the quality and quantity of the food consumed. There was no great dietary overlap between these two species.

This paper analyses the age and growth pattern of the four-spotted megrim (Lepidorhombus boscii), collected in the north Aegean Sea. The otoliths of the species exhibit bilateral asymmetry. Our data indicates that males have shorter lifespans (0–6 y) than females (0–8 y) and reach lower asymptotic lengths. A significant difference in growth rate exists between the two sexes after the first year of life. Growth in length is greater in females than males, whereas males appeared to be heavier than females of the same size. The latter was also corroborated by the higher accumulation of lipids in the muscle of males in relation to females. The growth rate of the species in the Atlantic was higher than in the Mediterranean. The oligotrophic character of the study area seemed to have a negative effect on the growth of megrims.

Zooplankton biomass varies on temporal, horizontal and vertical scales. However, data sets which incorporate all these dimensions at high resolution are very rare. Two devices which measure all these aspects have recently been simultaneously deployed in the Celtic Sea, the continuous plankton recorder (CPR) and the Longhurst–Hardy plankton recorder (LHPR). This demonstrates that integrated biomass derived from the LHPR are not significantly different from those derived using the CPR. Values have, therefore, been combined for the first time to describe the vertical distribution of mesozooplankton biomass at the Celtic Sea shelf edge through an annual cycle. This suggests that the surface biomass peak is broader at the shelf break than in the open ocean and in the autumn the main biomass peak may be below the depth sampled by the CPR.