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.

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 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.

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.

In Mont Saint-Michel Bay, one of the most abundant food items in young sea bass diets was Mytilus edulis. This invertebrate is an abundant cultured bivalve in many coastal systems and it is known to be in direct trophic competition with the natural food items of sea bass. This study shows that mussel culture can play the role of a nursery area, providing food for young opportunistic fish. Quantification of these interactions appears to be of a major importance in order to enable sustainable management of coastal areas.

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.

A new mechanism of demosponge spicule formation was recognized during taxonomic studies of bioeroding sponges (Porifera: Demospongiae: Clionidae). To date different spicule types have been explained by matching structures to their organic matrix, the axial thread. Bulbous structures, however, do not have an organic counterpart. Immature spicules of Cliona tinctoria and Pione caesia have irregular, rough heads. Higher magnification during scanning electron microscopy shows that silica granules are deposited regionally to form bulbs. Later silica secretion smoothens the bulb surface. Silica deposition in form of granules rather than in layers appears to be a structuring tool in tylostyles.

Otoliths from the stomachs of 138 by-caught grey seals (Halichoerus grypus) from the west coast of Ireland were compared with otoliths from the stomachs of 364 commercially caught cod(Gadus morhua) to determine if there were any overlaps in type, number and size of prey that might be attributable to secondary ingestion. A total of 19 species/groups were common to both cod and seal stomachs accounting for 99·6% and 95·8% of the otoliths from cod and seal stomachs respectively. There were significant differences between the otolith/fish lengths of all six species/groups compared but there were overlaps in the size distributions. Analysis of the diet composition of the cod stomachs suggested that larger cod consumed mainly fish and smaller cod consumed mainly crustaceans. Cod and seals were utilizing the same fish prey but the seals were generally consuming larger fish. Overlaps between the size distributions of prey species/groups suggest that secondary ingestion was possible and should be considered in future seal diet studies.

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.

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.

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.

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.

Observations and censi of the echinoid Paracentrotus lividus over 40 y at Lough Hyne marine nature reserve have revealed population fluctuations of >4 orders of magnitude. The P. lividus population has been anomalously low since the mid 1980s. The population age–size structure has also changed considerably and is now dominated by older individuals. Sea temperature is a known and important determinant of spawning (and recruitment) in this species. In certain years sea surface temperatures (SST) may not reach critical values for P. lividus mass-spawning to be triggered. In addition, toxic dinoflagellate blooms may have been responsible for large-scale mortalities within short periods. Years of anomalously low SSTs match the timing of critical decreases in the Lough Hyne P. lividus population. Years with low maximum SSTs coincide with the timing of major El Niňo Southern Oscillation (ENSO) events. We suggest a SST and possibly ENSO link to unfished (Lough Hyne) P. lividus population changes and propose such links as potential aggravating factors in the decline of the fisheries.

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.

Biological data are presented on two specimens of Taningia danae, an adult female caught by a trawler in Galician waters (north-west Spain) and a juvenile caught in a deep-water research trawl in Scottish waters (UK). The species has not previously been recorded in either area, although its presence has been inferred from beaks found in sperm whale stomach contents.

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.

The gastropod Littorina littorea shows increased mortality in the summer months when infected with digenean parasites. One possible cause of this mortality is impaired respiration in infected hosts. Respiration rates of L. littorea infected with three species of digenea of varying pathogenicity were measured: Cryptocotyle lingua, Himasthla elongata and Renicola roscovita. No evidence of altered respiration rates in infected snails was found.

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 demographic structure of a population of Paracentrotus lividus living in a coastal Mediterranean lagoon was studied in 1990. Analysis of this structure revealed that the population examined was made up of four distinct cohorts which represented individuals 2, 3, 4 and over 4 y of age. The variability in demographic structure as a function of biotope revealed that sea urchin migration occurred from the pebble area (recruitment area, high sea urchin density and overgrazing facies) towards areas made up of Cymodocea nodosa sea grass beds (growth areas, low density and abundant prefered food). These migrations seem to have been caused by food limitation in the former biotope coupled with a shift in diet in young individuals.

A large, mature, female cirrate octopod, Cirroteuthis magna, was caught in a research trawl at 3200-m depth on the Cape Verde Terrace off the west African coast in November 1999. It is only the fourth recorded specimen of this species and the largest specimen (1,700 mm TL; 330 mm ML) of cirrate octopod ever caught. Detailed measurements were taken of the fresh and preserved specimen and indicated considerable shrinkage (17–32%) during formalin preservation. Careful dissection revealed large mature eggs (12·5–14 mm long) in the proximal oviduct, and a wide range of egg sizes and development stages in the ovary. The taxonomy and ecology of the species is briefly discussed.