In order to control the spread of the invasive Caulerpa taxifolia (Chlorophyta) in the Mediterranean, in situ experiments were conducted with the specialized predator Lobiger serradifalci (Mollusca: Ascoglossa=Sacoglossa). An unexpected effect of L. serradifalci on C. taxifolia was observed. Instead of destroying the algal frond, the ascoglossan cut fronds into tiny living fragments capable of regenerating. Thus, L. serradifalci may facilitate C. taxifolia dispersal instead of controlling it.

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.

Stomach contents of 382 Palinurus elephas collected in the Columbretes Islands Marine Reserve (north-western Mediterranean) were examined to study the diet and to assess ontogenetic and sex related differences in feeding regime. Molluscs, crustaceans, and sea urchins were the most common prey. Diet composition varied with lobster size but not with sex. Ontogenetic changes in diet were reflected in the progressive reduction of the contribution of gastropods and crustaceans and in the increased importance of other prey such as fish.

This study examined the inter-relationships between molluscs, heavy metal concentrations and trematode parasites. Littorina littorea (Mollusca: Gastropoda) were sampled seasonally from two sites in a tidal lagoon. Site A was close to the inflow of a polluted stream whilst site B was at the opposite end of the lagoon. The samples were analysed for lead, iron, copper and nickel. Metal concentrations in L. littorea varied with site, season and parasite infection, and exceeded comparative non-polluted concentrations for all metals in some samples. Parasitized periwinkles consistently had significantly lower levels of iron, copper and nickel than uninfected periwinkles.

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.

This study investigated the features of mudballs produced by male and female Uca annulipes. Both sexes formed mudballs from mud excavated from within the burrow during the final hour of the low tide period. Males placed the centre of the mudball aggregation and the furthest mudball significantly further from the burrow than females. These observations suggest that the placement of male mudballs was not simply a by-product of burrow excavation.

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.

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.

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 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.

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.

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.

Microsatellite loci are one category of genetic markers that are frequently highly polymorphic. As such they have proved to be extremely useful tools for examining the population biology of many different taxa, and offer the potential to discriminate among fish stocks. Here, four new polymorphic microsatellite loci in the European plaice, Pleuronectes platessa are reported. In addition, data are provided on the utility of all published plaice microsatellite loci in flounder (P. flesus), lemon sole (Microstomus kitt) and Dover sole (Solea solea).