Chlorophyll-a (chl-a) distribution and associated physical (temperature, salinity) and chemical (dissolved oxygen) conditions off northern Chile (Humboldt Current System), during the austral summer (February–March) and autumn (May) of 1994, were studied in the region bounded by ∼18–24°S and 70–72°W (out to ∼200 km from the coast; 0–100 m depth); within this region, nutrients were measured in an area of persistent coastal upwelling (∼19–22°S, out to 80 km from the coast). Temperature and salinity distributions, as well as nutrient concentrations, indicated the occurrence of active upwelling during both cruises. Also, and together with maps of geopotential anomaly (0/200 dbar) and depth of the thermocline (15°C isotherm), their distribution suggested the presence of a mainly equatorward flow, anticyclonic eddy-like structures, and intrusions of warm (>19°C), high salinity (>35·0 psu), subtropical water towards the coast. A tongue of cooler and lower salinity water, and of lower flow fields, extended from the coast towards the offshore zone during both sampling periods, in association with higher chl-a concentrations (>1 mg m−3, >20 mg m−2 between 0 and 25 m depth) and predominance of net-phytoplankton (>20 μm). The comparison of these results with those for the winter and spring of 1993 in the same area suggest a relatively weak seasonal signal in chl-a concentration during the 1993–1994 period, with higher water column concentrations during the summer and spring periods in the selected upwelling area, though surface chl-a concentrations for the whole of the area did not vary significantly.

The introduction of non-indigenous marine plankton species can have a considerable ecological and economic effect on regional systems. Their presence, however, can go unnoticed until they reach nuisance status and as a consequence few case histories exist containing information on their initial appearance and their spatio–temporal patterns. Here we report on the occurrence of the non-indigenous diatom Coscinodiscus wailesii in 1977 in the English Channel, its subsequent geographical spread into European shelf seas, and its persistence as a significant member of the diatom community in the north-east Atlantic from 1977–1995.

Zooplankton was collected by a diver-towed net close to the substratum at four depths (0, 6, 12 and 18 m) over a 17 month period in three locations in Lough Hyne, Co. Cork, Ireland. Zooplankton was identified to phylum or class levels and mean numbers were calculated for each taxon, site and depth. Seasonality was observed in several meroplanktonic groups (Echinodermata, Nemertea, Mollusca and fish postlarvae), and in gelatinous zooplankton. Depth preference was found to be statistically significant in the polychaetes (larvae and pelagic species), molluscan and ascidian larvae. However, the influence of depth on overall zooplankton community composition was found to be negligible. Sampling location, adjacent substrata and flow conditions were found to influence zooplankton in that area.

Octomagelona bizkaiensis (Annelida: Polychaeta), a new genus and species of the family Magelonidae is described from the north-eastern Atlantic. The specimens were collected from the Capbreton Canyon, Bay of Biscay, at a depth of 1000–1040 m. The new genus and species differs from all known genera and species of the family Magelonidae by the presence of eight instead of nine thoracic chaetigers.

A new species Spiochaetopterus nonatoi is described from the south-eastern coast of Brazil, the type locality being Flamengo Bight, 6-m depth (23°30′S 45°06′W). This species is distinguishable from already erected species of the same genus by the following characteristics: oculate specimens of large size; maximum segments, 197 (N=15); maximum tube length, 45 cm; maximum body length, 20 cm; orange coloration of the fore part (peristomium and segment 1) and of the ventral shield on segments 6–7; shape of the specialized enlarged cutting seta on A4 with an obliquely truncated distal end; this slightly concave section is heart-shaped and clearly asymmetrical; segments B1 and B2 with one lobe on the neuropodia. This additional description in the genus Spiochaetopterus confirms the limited geographical area of each species in this genus. In spite of the probable ability of planktonic larvae of Spiochaetopterus to disseminate throughout the Atlantic Ocean, the benthic adults of each species cover only a limited geographical area. In particular, the stem species S. costarum loses its cosmopolitan character.

Scanning microscope investigations were carried out on mandibles, labrum and paragnaths of several species of Mysidacea and Euphausiacea. Gut content analyses were in agreement with morphological observations. It appears that the morphology of the peri-oral structures and especially of the mandibles reflect the feeding habits, and that the well known relationships between the size of the molar process and the incisor one, i.e. a large molar process is associated with herbivorous feeding, is not always verified. Bacescomysis abyssalis and Bentheuphausia amblyops are believed to be mostly saprophagous, Boreomysis inermis and Meganyctiphanes norvegica are mostly phytophagous, Hemimysis speluncola is omnivorous, while Siriella armata and Thysanopoda orientalis are carnivorous species.

The red whelk, Neptunea antiqua (Mollusca: Prosobranchia) is a dioecious prosobranch species with internal fertilization, and lecithotrophic larval development. Sexual dimorphism, sexual ratio, the size and age at sexual maturity, and the annual breeding and hatching periods of this subtidal neogastropod were investigated in the central western Irish Sea. Sexual dimorphism was evident as female whelks were larger in both length and weight. Subtle differences in shell morphology were also detected between the sexes. All samples taken together indicated an equal male to female sexual ratio for the studied population. Size and age at sexual maturity were noted to differ between sexes, occurring at 75–90 mm (shell length), or four to five years in males, and 95–110 mm, or six to nine years in females. Quantitative and qualitative techniques identified an annual spawning period between late spring and early summer. Egg masses containing between 14 and 84 egg capsules were observed attached to the dorsal surface of whelk shells in the succeeding months. An average fecundity of 63·78 juveniles was estimated per egg mass deposited. Juveniles were observed to hatch after 6–7 months in laboratory maintained aquaria, indicating a hatching period from October to January in the Irish Sea.

Loripes lucinalis, a littoral bivalve harbouring endocellular sulphur-oxidizing bacteria within its gills, was studied between September 1991 and September 1992 at the Moulin Blanc beach (Brittany, France). The general macro-anatomy of the gill consists of bacteriocyte channels and cylinders made up of two cell types, namely bacteriocytes and intermediate cells. In addition to the usual assortment of cell organelles, the bacteriocytes contain bacterial cells, electron-dense inclusions and large granular bodies. The bacteria are numerous within the bacteriocyte zone, representing 55±8% of the gill cross-sectional surface area. Acid phosphatase activity is detectable within the gill tissue both in proximity to and within the bacterial cells. The electron-dense inclusions and large granular bodies also stain positively for acid phosphatase suggesting that these bodies represent different phases of endosymbiont digestion. Bacterial lysis may be an important means of providing L. lucinalis with its nutritional requirements. The granular bodies stain positively for acid polysaccharides and the percentage of the gill cross-sectional area occupied by lysed granular zones varied as a function of sampling period. The percentage of total body weight represented by the gill was significantly lower in March compared to September, October and January, all other months being intermediate. The decrease in gill percentages and the levels of gill lysis correspond remarkably well to gamete development.

The effects of sublethal tributyltin (TBT) concentrations on the growth and development of Ruditapesdecussatus larvae were studied. Veliger larvae of R. decussatus were exposed to TBT nominal concentrations of 25, 50, 75 and 100 ng Sn l−1 in the water for a period up to 13 d. Larval growth and development were chosen as endpoints for evaluation of TBT toxicity. Growth of R. decussatus larvae was severely affected by TBT concentrations (25–100 ng Sn l−1). A 3- to 6-fold reduction growth was observed in these early larval stages. Furthermore, R. decussatus larvae exposed to TBT did not develop further than D-larvae while the unexposed ones reached the umbonated stage.

Four Benthoctopus species are recognized in the waters of the Falkland Islands: B. eureka, B. magellanicus, Benthoctopus sp. A, and Benthoctopus sp. B. Initial oocyte reserve of B. eureka is 250–535 eggs, the actual fecundity is 75–234 eggs while the rest of the oocytes degenerate at maturation. Larger females have higher fecundity. Gonad maturation of Benthoctopus sp. A and Benthoctopus sp. B follows a similar pattern. The Benthoctopus egg masses contained 170–190 eggs. The hatchlings possess arms that are much longer than mantle length with a large number of suckers, and do not have discernible chromatophores.

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 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.

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.

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.

Assessment of spawning survival for female capelin Mallotus villosus (Pisces: Osmeriformes) greater than 12 cm in length was made in the autumn of 1995–1997 comparing a histological technique with existing methods. An intensive macroscopic visual assessment of selected samples from 1995, 1996 and 1997 revealed that 10, 20 and 40% of the females were recovering from spawning respectively each year. Histological assessments of the same fish revealed that 20% in 1995, and nearly 60% of the fish in 1996 and 1997 showed physiological evidence of previous spawning. The proportion of recovering spawners increased with both length and age of the fish. One sample from the Northwest Atlantic Fisheries Organization area of 2J during October 1997 contained nearly 90% recovering fish. The potential impact of the fishery in light of the variability in post-spawning survival of the iteroparous female capelin is discussed.

The embryonic and early larval development of the laboratory-reared tub gurnard, Trigla lucerna are described. The eggs ranged in diameter from 1·33 to 1·40 mm, with a mean of 1·36±0·236 mm, were pelagic and spherical with a homogeneous and unsegmented yolk. There was single oil globule in the eggs. Globule ranged in diameter from 0·25 to 0·29 mm (mean 0·28±0·012 mm). Embryonic development lasted 115 h 2 min at mean temperature 13·5 °C. Newly-hatched larvae were 3·09±0·014 mm in total length. Absorption of the yolk sac was complete after the sixth day, when larvae reached 4·85±0·015 mm in total length. The only character for identifying eggs among species could be diameter, since the values obtained are lower than those obtained for Eutrigla gurnardus and Aspitrigla cuculus, but larger than those for Trigloporus lastoviza. The length of newly hatched yolk-sac larvae of tub gurnard is significantly lower (t-test, P<0·05) than those of most of the other gurnard species. Characters likely to help in identification of species will probably prove to be the length, shape and pigmentation of the pectoral fin, and the degrees of development of spiny armature on the head.

In the Mediterranean Sea, the most conspicuous cleaner fish is the wrasse, Symphodus melanocercus, a specialized cleaner wrasse. In this fish species, energetic investments in reproduction are different for males and females. Female S. melanocercus were found to be more active in cleaning and ingested significantly more gnathiid isopod larvae than males. Male cleaners foraged more on benthic animals and showed a strong preference for clients according to their mucus characteristics. Results indicate that female S. melanocercus are more likely to be specialized, in terms of cleaning behaviour, than males. We suggest that females are more honest than males and that they play an important role in preserving the good reputation of S. melanocercus as a cleaner fish.

The main prey species in the summer (July–September) diets of harbour seals (Phoca vitulina) on the Island of Mousa (Shetland, UK), 1994–1997, were whiting (Merlangius merlangus), herring (Clupea harengus), sandeel (Ammodytidae) and garfish (Belone belone). Norway pout (Trisopterus esmarkii) was numerically important but comprised no more than 11% of prey weight in any year. There were marked between-year fluctuations in the relative importance of these prey, with whiting comprising 16–34% (by weight) of the diet, herring 12–28%, sandeels 7–18% and garfish 7–22%. Additional data on spring (April–June) diet were available for 1995–1997: sandeels were the most important prey (% weight) in all three years (51–60% of the diet), while herring (8–48%) and gadids (2–22%) varied in importance. The average size of fish eaten was larger than that reported in comparable studies from other areas. Harbour seals appear to have selected larger sandeels, whiting and Norway pout than the average size available in the area, as indicated by survey trawls, although between-year changes in the size of Norway pout in the diet did to some extent reflect availability. Interannual variation in the importance of Norway pout in the diet appeared to track trends in abundance, although the short time series precluded detection of a statistically significant correlation. Thus, some of our results are consistent with harbour seals feeding opportunistically while others point to selectivity, particularly for prey size. Estimated consumption of fish by the 500 harbour seals on Mousa during summer ranged from 152–195 tonnes.

With this note we contribute to the discussion on the appropriate level of taxonomic resolution required in benthic monitoring studies. In a set of multivariate analyses using data from different taxonomic levels and various data transformations we show that similar results are obtained on the levels of species to families, almost irrespective of the transformation used. For taxonomic levels above that of orders, transformation results in different plots and especially presence/absence transformation reduces the discrimination of sites. We recommend guiding the choice of transformation by biological considerations and adjusting the taxonomic sufficiency to the objective of each study.

To evaluate the potential for sediment reworking of two deposit-feeder polychaetes, daily sediment expelled per single worm has been estimated in laboratory experiments on 20 specimens of Nainerislaevigata and 20 of Notomastus latericeus. Both species showed very low values of daily sediment expelled especially when compared to literature data concerning other polychaetes. In both species reworking response was correlated to the dry weight of the worms and appeared higher in Nainerislaevigata, displaying the largest biomass. This species also revealed a greater mobility in situ than Notomastus latericeus which could be considered more as a tube dweller than a burrower.